Edn 0504 Supplement

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S P E C I A L

S U P P L E M E N T

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E D N

NOVEMBER 2005

A Digital Power Revolution

90% Reduction in Components, PCB Traces, and Development Time Z-One™ Digital IBA Integrates Power Management and Conversion ■ ■ ■

System-level component count reduction improves cost, reliability, and power density. GUI configuration and simulation dramatically simplifies power system development. Industry-leading power conversion and management capabilities include programmable output voltages, sequencing, tracking, and protection limits. I2C Bus

Z-Series Digital Power Manager ■ ■

■

Single-wire Z-One Digital Bus 48V

Programs and manages Z-POL™ converters. Monitors intermediate bus, accepts external interrupts, and initiates crowbar protection. Facilitates Z-POL performance telemetry for remote monitoring and fault management.

Z-POL (Point-Of-Load) Converters ■

IBA Bus

■

Vout 1

Vout 2 Vout 3 (Up to 32 Outputs)

■

Programmable 0.5 to 5.5VDC outputs using 3.0 to 13.2VDC inputs. Current densities up to 39 amps/in2. Real-time reporting capabilities include voltage, current, and temperature.

www.power-one.com • 800.678.9445 • 805.987.8741 Power-One and the Power-One logo, Z-One, ZIOS, Z-POL, and the Z Digital IBA logo are trademarks or registered trademarks of Power-One, Inc.

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A L L T H I N G S E L E C T R O N I C— S T A R T W I T H M I C R O C H I P

Getting started in embedded design is easy with PIC® Microcontrollers

Microchip offers a variety of low pin count 8-bit PIC microcontrollers that are extremely simple to use and fit in practically any application!

WIN THIS!!!

Our PIC microcontrollers are not only powerful and flexible, but are supported with tools and resources to ease you into embedded design. With superior technical services, low-cost development tools, full NEW! PICkit™ 2 Flash Starter Kit for low-cost development of Microchip’s documentation, online discussion groups and numerous other resources, 8-bit PIC® microcontrollers. Visit our web site to enter it has never been easier to start developing with PIC microcontrollers! the Start Now Design Contest!

Architecture Cost-Effective Baseline PIC Microcontroller*

Peripheral-Rich Mid-Range PIC Microcontroller

Product Series

Program Word

Pin Count

Flash Program Memory (Bytes)

PIC10F

12-bit

6

384 to 768

4 to 8 MHz

8-bit

•

PIC12F

12-bit

8

768 to 1536

4 to 8 MHz

8-bit

•

PIC16F

12-bit

14 to 40

768 to 2048

4 to 8 MHz

8-bit

•

PIC12F

14-bit

8

1792 to 2048

32 kHz to 8 MHz

10-bit

•

•

•

•

PIC16F

14-bit

14 to 64

1792 to 14336

32 kHz to 8 MHz

10-bit

•

•

•

•

Internal Oscillator

ADC

Comparators

Capture/ Compare/ Pulse-Width Modulation

nanoWatt Technology†

Data EE

*Easily migratable to Mid-Range PIC Microcontroller Architecture; † Microchip’s proprietary low power technology.

www.microchip.com/StartNow Start Now with a career at Microchip! Visit www.microchip.com/careers for a current listing of open positions throughout the world. The Microchip name and logo, the Microchip logo and PIC are registered trademarks of Microchip Technology Incorporated in the USA and in other countries. PICkit is a trademark of Microchip Technology Incorporated in the U.S.A. and other countries. ©2005 Microchip Technology Incorporated. Allat rights reserved. Enter xx www.edn.com/info

PART FOUR: EMBEDDED POWER

Reed Business Information 225 Wyman Street, Waltham, MA 02451 Phone: (781) 734-8000 www.edn.com

EDN Worldwide Stephen Moylan, President, Boston Division/Publishing Director Phone: (781) 734-8431 Fax: (781) 290-3431 [email protected] Cindy Fitzpatrick, Director EDN Custom Publishing Services Phone: (781) 734-8438 Fax: (781) 290-3438 [email protected] Heather Wiggins Web/CPS Production Coordinator Phone: (781) 734-8448 Fax: (781) 290-3448 [email protected] Contributing Editors: Linnea C. Brush Senior Research Analyst [email protected] Jeremiah Bryant Research Analyst [email protected] Jeff Shepard President [email protected]

ADVERTISER INDEX

American Power Design . . . . . . . . . .P24 Bear Power Supply . . . . . . . . . . . . . .P24 Bel Fuse . . . . . . . . . . . . . . . . . . . . .P19 Darnell Group . . . . . . . . . . . . . . . . . .P6 Digi-Key Corporation . . . . . . . . . . . . . .P3 Fairchild Semiconductor . . . . . . .Cover 4 Gaia Converters . . . . . . . . . . . . . . . .P30 International Rectifier . . . . . . . . . . . .P11 Intersil . . . . . . . . . . .P8, 21, 26, Cover 3 Kepco Inc . . . . . . . . . . . . . . . . . . . .P29 Linear Technology Corporation . . . . . .P25 Martek Power . . . . . . . . . . . . . . . . .P15 Micrel . . . . . . . . . . . . . . . . . . . . . . .P28 Microchip Technology Inc . . . . . . . . . .P4 National Semiconductor . . . . . . . . . . .P7 Norvell Electronics . . . . . . . . . . . . . .P23 Power Integrations Inc . . . . . . . . . . .P12 Power-One . . . . . . . . . . . . . . . . .Cover 2 Spellman High Voltage . . . . . . . . . . .P20 Vicor . . . . . . . . . . . . . . . . . . . . . . . .P31

6 Letter from the Editor 9 Embedded Power Supplies Reach New Heights

13

CASE STUDY: LINEAR TECHNOLOGY CORPORATION

How to Provide a Full-featured Embedded POL DC/DC Converter

16 AC Powering Semiconductor Growth

18 CASE STUDY: TEXAS INSTRUMENTS

Scalable Power Systems Meet the Needs of Configurable Blade Servers

22

CASE STUDY: FAIRCHILD SEMICONDUCTOR

PFC/PWM Combo IC Enables Best Power and Board Space Efficiency in LCD TV’s

27

CASE STUDY: POWER-ONE, INC.

Which Voltage Bus is Best?

Review the EDN Embedded Power and Control Online Source List at www.edn.com/supplements

NOVEMBER 2005 • EDN POWER TECHNOLOGY P5

PART FO U R: EM BED D ED POWER A SPECIAL S U P P L E M E N T TO

EDN

LETTER from the EDITOR he market for embedded ac-dc power supplies and dc-dc converters is currently being driven by a number of technologies, including blade servers, Power-over-Ethernet (PoE), and the intermediate bus architecture (IBA). Combined with digital power management and control, opportunities are emerging for higher wattage converters. Blade servers are seeing growth that is more than three times faster than the server market as a whole, and their growth is one driver pushing the IBA. As a result, large original equipment manufacturers that were reluctant to move towards the IBA are now employing it in their higher performance systems. In this issue, Texas Instruments discusses how they helped a customer design a scalable power system to meet the needs of configurable blade servers. Both space and cooling are at a premium in networking systems powered via a 48V backplane. Therefore, it is extremely important for point-of-load converters to be both compact and efficient. Linear Technology provides a case study on supplying a POL dc-dc converter for embedded systems that meets or exceeds the multiple constraints of limited space and cooling within a given enclosure. Powering challenges on the ac input side are equally demanding, with power factor correction (PFC), hot swappability, and pulse width modulation (PWM) posing special challenges. Semiconductor companies are providing products for this side of the house that range from digital PWM to One Cycle Control for PFC. PFC, in particular, is gaining attention as new harmonic standards become mandatory in Europe and Japan, and efficiency programs (such as Energy Star) prescribe limits to power consumption. To address PFC regulations, Fairchild Semiconductor designed a PFC/PWM combo integrated circuit to enable power and board space efficiency in LCD televisions. As regulations change, and as digital power moves into the commercial mainstream, opportunities will emerge for power supply manufacturers to increase efficiency and reduce costs. Power-One’s case study looks at how they helped a customer choose the right intermediate bus voltage by using a digital power management system. The variety of solutions being offered, and the standards to support them, ensure that embedded power supplies will remain one step ahead of system needs.

LINNEA C. BRUSH Senior Research Analyst Darnell Group

P6 E D N P O W E R T E C H N O L O G Y • N O V E M B E R 2 0 0 5

New Alternatives for Next-Generation DC-DC Conversion Whatever Topology You Choose, National Has the Power Management Solution Alternative 1:

LM5041 Current-Fed Converter

LM5041 Current-Fed Converter • Buck stage regulates input to push-pull or full-bridge isolation stage • Accommodates wide input voltage range • No output filter inductors required • Lower voltage stress and switching loss in push-pull switches • Ideal for multiple high-power outputs • Optimized for synchronous rectification

Alternative 2:

LM5033 IBC

LM5033 Intermediate Bus Converter (IBC) • Isolated step-down converter stage feeds multiple non-isolated point-of-load (POL) converters • Each output is independently regulated • No feedback opto-coupler required • Integrated start-up regulator • Low primary component count • Tiny, thermally enhanced LLP® packaging

© National Semiconductor Corporation, 2005. National Semiconductor, All rights reserved.

For FREE samples, evaluation boards, datasheets, and more, visit us today at: power.national.com Or call 1-800-272-9959

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, and LLP are registered trademarks of National Semiconductor Corporation.

Intersil Switching Regulators Intersil High Performance Analog

What’s Black, White, and Cool All Over? Maintaining IC temperatures doesn’t have to be a riddle. Intersil's new high current Integrated FET Regulators have the industry's only true Thermal Protection with auto shut down at 135°C. Intersil's EL7554 and EL7566 DC-DC buck regulators with internal CMOS power FETs operate from 3V-to-6V input voltage and are capable of up to 96% efficiency. But what's really cool about these devices is ground breaking features like built-in Thermal Protection and Voltage Margining for actual in-circuit performance validation.

The first line of defense against heat is a thermally-efficient HTSOP-28 package, which utilizes an exposed thermal pad underneath the IC to spread heat through the PCB.

Key Features: 4A (EL7554) and 6A (EL7566) continuous output current Up to 96% efficiency Built-in 5% voltage margining 3V-to-6V input voltage

The VTJ pin is a formula-based, accurate indicator of the internal silicon junction temperature.

If all else fails and the temperature sensor indicates a junction temperature above 135°C, the PWM Regulator will shut down.

0.58 in2 (EL7554) and 0.72 in2 (EL7566) footprint with components on one side of PCB Adjustable switching frequency to 1MHz

For more information and samples, go to www.intersil.com/edn Easy-to-use simulation tool also available. Modify switching frequency, voltage ripple, ambient temperature and view schematics waveforms, efficiency graphs and complete BOM with Gerber layout. www.intersil.com/iSim

Intersil – Switching Regulators for precise power delivery. ©2005 Intersil Americas Inc. All rights reserved. The following are trademarks or services marks owned by Intersil Corporation or one of its subsidiaries, and may be registered in the USA and/or other countries: Intersil (and design) and i (and design).

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PART FO U R: EM BED D ED POWER A SPECIAL S U P P L E M E N T TO

EDN

Embedded Power Supplies Reach New Heights 8 by JEREMIAH BRYANT number of trends are converging that are pushing embedded ac-dc power supplies and dc-dc converter modules towards higher wattages. Rapidly growing blade servers, Power-over-Ethernet (PoE) equipment and several other devices are driving power requirements higher. Shifting bus architectures have an even larger effect on the embedded power supply market. These shifts range from the growing usage of the intermediate bus architecture (IBA), to alternative powering trends, to the biggest potential change— digital power control and management. Combined, these trends are driving opportunities for higher wattage converters. Gains made by the IBA and its hallmark bus converters are a primary driver of this trend. While the IBA is clearly not new, the market acceptance of the IBA is continuing to grow. Large OEMs that were reluctant to move towards the IBA are now employing it in their higher performance systems. Blade servers are seeing growth that is more than three times faster than the server market as a whole. Currently blades account for a small portion of the server market, their growth is one driver pushing the IBA. Recently, a number of companies have released new bus converters that illustrate growing interest in 2000

1500

1000

500

0

<4W

4-12W

13-24W

25-49W

50-99W 100-249W 250-500W >500W

2005 2010

Worldwide DC-DC converter module market by wattage (millions of dollars)

the IBA. Power-One added a 46A quarter-brick bus converter to its product line that delivers 441W. Tyco Electronics introduced the QBK033 bus converter, which the company claims was the first 400W quarterbrick power module. Artesyn Technologies increased the wattage of its highest power quarter-brick bus converter to 450W, a 150W improvement over its earlier generation quarter-brick bus converter. Similarly, the growing usage of the IBA is driving sales of Point-of-Load (POL) converters. The worldwide non-isolated dc-dc converter market, including POLs and voltage regulator modules, is Figure 1: Artesyn increased the power of outpacing the dc-dc converter its latest Typhoon quarter-brick bus market as a whole. According converters to 450W to the Darnell Group, revenues in this market are projected to rise from $760 million in 2005 to $1.4 billion in 2010. A number of new product offerings from companies in the Point-ofLoad Alliance (POLA™) illustrate this trend. Ericsson Power Modules recently introduced 17 POLA-interoperable POLs in three platforms with current ratings from 6A to 60A. One of these POL families, the PMM series, is aimed at current-thirsty highend computer applications. It delivers 60A, while achieving a 96% peak efficiency. Artesyn has developed 50A and 60A POL converters for the telecom and datacom markets including blade servers, data storage switches and voice-processing systems. Texas Instruments has introduced the PTVxx010 8A and PTVxx020 18A families of POLA compatible plug-in power modules. While POLs are not specific to the IBA, the growth of POLs coupled with the

NOVEMBER 2005 • EDN POWER TECHNOLOGY P9

PART FO U R: EM BED D ED POWER A SPECIAL S U P P L E M E N T TO

EDN

converters using the SMBus in expanding bus converter market illusorder to configure, control and trates the growing usage of the IBA. monitor PMBus compatible While the IBA is creating architecturdevices, such as converters or al power shifts within the system's box, Figure 3: Power-One has expanded its power supplies. However, the PoE is changing power requirements outZ-1000 No-Bus family to include 7A, PMBus is only a communicaside of the box. Like the IBA, PoE is 15A and 20A POLs tions standard and companies changing the power distribution mechanism from the wall plug to the load. In PoE, power sourc- are still developing complete digital power conversion ing equipment (PSE), typically either a PoE endspan inte- product lines. While there are a number of differences grated into an Ethernet switch or a PoE midspan, deliver between the two approaches, the primary difference power to a powered devices (PD), such as a VoIP phone, stems from the communications protocols and the manner in which the parameters are set. Wi-Fi access point, flat panel PC and so on. Power-One has two digital strategies. The first The PoE strategy increases power requirements for the centralized PSE, especially for ac-dc front strategy is the I2C proends, but typically replaces the power supplies for the grammable Z-7000 POLs PDs with discrete components. Currently, PoE deliv- which are programmed ers only a maximum of 15.4W per port, which limits using the company's prothe type of PDs that PoE can power and also limits prietary software and can the power requirements of the PSE. However, the be reprogrammed at any IEEE has formed a study group that is examining time. Power-One's addi- Figure 4: Astec Power’s first offering from its PoE-Plus, with the goal of at least doubling the power tional strategy is the one Digital Power Initiative is the 50W DTX dc-dc level to 30W per port and possibly as high as 100W. time programmability converter, which features integrated digital control with bi-directional PMBus If PoE-Plus gains steam, ac-dc front ends will see a found in the Z-1000 Nocommunication greater opportunity, as will dc-dc converter modules. Bus™ POLs. These POLs Trying to capitalize on the growing PoE market, provide power management capabilities without havAstec Power has introduced the DS657, a 657W ing to implement external controllers and other assopower supply for PoE implementations. Phihong has ciated components. introduced a 275W power supply with integrated 24Another digital communications approach origiport PoE injection. Power Integrations has designed nated from a collaborative open standard—the PMBus. new solutions for the PoE market, as they expanded So far, Texas Instruments, Zilker Labs and Silicon Labs their DPA-Switch™ family have digital power controllers, but PMBus-complaint of ICs to include an option digital dc-dc converters are just now hitting the market. for PoE. Several new digital products were unveiled at the The growing IBA mar- Digital Power Forum or shortly after. Artesyn Techket is also yielding opportu- nologies announced a PMBus-compliant digitally pronities for digital power con- grammable dc-dc converter. The DPL20C is a non-isotrol and conversion lated POL that features digital configuration, monitorbecause systems that use ing and diagnostic facilities accessible via the PMBus this architecture are going interface. The 20A POL provides a programmable outto be the early digital put voltage from 0.6V to 5.5V, programmable sequencadopters. Thus far there ing, tracking and margining and real-time voltage, curhave been two primary dig- rent and temperature monitoring. Astec's first offering ital implementation strate- from its Digital Power Initiative is the PMBus-complaint Figure 2: Ericsson power modules gies. The first strategy is DTX dc-dc converter. The DTX features integrated digintroduced 17 POLA-interoperable POLs Power-One's proprietary Z- ital control with bi-directional PMBus communications capable of delivering 6A to 60A One™ Digital IBA which is and includes self-diagnostics, efficiency optimization a complete digital product line for the IBA. The sec- and output impedance control in addition to dynamic ond approach stems from the PMBus™ which defines a standard way to communicate with power (“Embedded Power” continued on P33)

P10 E D N P O W E R T E C H N O L O G Y • N O V E M B E R 2 0 0 5

CAN YOUR BRICK DO THIS? IR’s DC Bus Chipset Enables Bricks With 48Vin, 9.6Vout, 330W at 97% Efficiency Full-Bridge Bus Converter Chipset (IRF6646, IR2086S, IRF6635 ) 48Vin / 9.6Vout / 175kHz

98

97%

Electrical Efficiency (%)

96 94 92 90 4 x (80V) IRF6646 Primary 2 x (30V) IRF6635 Secondary

88 86 84 82 0

5

10

15

20

25

30

35

Load Current (A)

Full Bridge DC Bus Converter

Reference Designs Available

New DC-DC Chipset Solution from International Rectifier DirectFET™ MOSFETs Part # Package VDSS IRF6644 IRF6655 ★ IRF6646 IRF6613 IRF6614 ★ IRF6635

Medium can Small can Medium can Medium can Small can Medium can

100V 100V 80V 40V 40V 30V

RDS(on) max @ VGS=10V 13mΩ 62mΩ 9.5mΩ 3.4mΩ 8.3mΩ 1.8mΩ

QG Typical 35nC 8.7nC 36nC 42nC 19nC 47nC

QGD Typical 11.5nC 2.8nC 12nC 12.6nC 6.0nC 17nC

Control IC Part # Package Voltage Rating Description Primary-side half-bridge control IC, IR2085S SO-8 100V fixed 50% duty cycle, self-oscillating Primary-side full-bridge control IC, ★ IR2086S SO-16 100V fixed 50% duty cycle, self-oscillating

International Rectifier’s new power management DC Bus converter chipset delivers 48V in , 9.6V out , over 330W at 97% efficiency for networking and telecommunications systems. • Single DirectFET MOSFET can replace two SO-8 devices • Reduces component count by > 45% • Achieves up to 1.5% better efficiency compared to industry standard quarter brick form factors • Reduces temperatures up to 40˚C • Board space reduced by 29% vs. quarter brick form factors • Industry Best RDS(on) for IRF6644 (13mΩ), IRF6646 (9.5mΩ), IRF6635 (1.8mΩ) Design Services available at www.mypower.com

★ – IR product featured in Full-Bridge Bus Converter reference design above IR's proprietary DirectFET technology is covered by US Patent 6,624,522 and other US and foreign pending patent applications. DirectFET is a trademark of International Rectifier.

for more information call 1.800.981.8699 or visit us at Enter xx www.irf.com/dcdc at www.edn.com/info

THE POWER MANAGEMENT LEADER

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PART FO U R: EM BED D ED POWER A SPECIAL S U P P L E M E N T TO

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CASE Study

New ICs Simplify Embedded POL DC/DC Converter Designs 8 by TONY ARMSTRONG, PRODUCT MARKETING MANAGER, POWER PRODUCTS GROUP, LINEAR TECHNOLOGY CORPORATION

the challenge

the solution

Most embedded systems are powered via a 48V backplane. This voltage is normally stepped-down to a lower intermediate voltage of either 12V or 5V to allow power to the racks of boards within the system. However, most of the sub-circuits or ICs on these boards are required to be powered at voltages ranging from 0.8V to 3.3V at currents ranging from tens of milliamps to tens of amps. As a result, a point-of-load (POL) dc/dc converter is needed to step down the 12V or 5V to the desired voltage and current level required by the subcircuits or ICs. Since space and cooling are at a premium in these systems, it is extremely important for any POL converters to be both compact and efficient. Furthermore, many microprocessors and digital signal processors (DSPs) need a core power supply and an input/output (I/O) power supply which must be sequenced during start-up. Designers have to consider the relative voltage and timing of core and I/O voltage supplies during power-up and –down operations to comply with manufacturers specifications. Without proper power supply sequencing, latch-up or excessive current draw may occur that could lead to damage to the microprocessor’s I/O ports or the I/O ports of a supporting device, such as memory, programmable logic devices (PLDs), field programmable gate arrays (FPGAs), or data converters. To ensure that the I/O loads are not driven until the core voltage is properly biased, tracking of the core supply voltage and the I/O supply voltage is necessary. Although start-up and shutdown tracking can be implemented externally for any given DC/DC converter, the power supply sequencing requirements will vary from system-to-system. These solutions include application specific standard products (ASSPs) that can be configured via a programmable interface or by external components; programmable microcontroller-based solutions and FPGA solutions.

Feature Rich IC Allows Optimum Flexibility The penalty for poor tracking or sequencing is often irreparable damage to devices in an embedded system. FPGAs, PLDs, ASICs, DSPs and microprocessors typically have CUSTOMER diodes placed between the core and PROFILE I/O supplies as a component of ESD A WORLDWIDE LEADER IN protection. If supplies violate the track- NETWORKING ing requirements and forward bias the SOLUTIONS FOR protection diodes, the device may be THE INTERNET damaged. Voltage sequencing, tracking, and margining have become popular features in dc-to-dc converter modules; however, these functions are less commonly found in dc/dc controller ICs. Linear Technology’s LTC3770 is an ideal solution for POL dc/dc conversion needs and is also distinguished by its fast transient response, a phase-locked loop (PLL) that allows synchronization to a system clock, and a highly accurate reference. Capable of operating from a 4V to 32V input, the current-mode controller can produce a stepped down output at currents up to about 25A, see Figure 1. The LTC3770’s constant on-time, valley current-mode architecture, combined with a very low minimum on-time (50ns typical), allows the control loop to respond quickly to load steps. The LTC3770 can perform RDS(ON) current sensing by sensing the voltage drop across the synchronous power MOSFET. Or for systems requiring more-precise control of output current, a conventional sense resistor can be used in the source of the lower MOSFET. In either case, the current limit is user-programmable. The controller can operate at very low duty cycles. In the extreme case, an output as low as 0.6V can be supplied from input voltages as high as 32V -

N O V E M B E R 2 0 0 5 • E D N P O W E R T E C H N O L O G Y P 13

PART FO U R: EM BED D ED POWER A SPECIAL S U P P L E M E N T TO

Figure 1. The LTC3770 steps down a 12V input to a 2.5-V output at 10 A

even under no-load conditions. In the applications where such low output voltages are required, the precision of the chip’s voltage reference becomes significant. The LTC3770 specifies an output voltage accuracy of ±0.5% at room temperature and ±0.67% from 0ºC to 85ºC. Across the device’s full operating temperature range (–40ºC to 85ºC), the total error on output voltage is still only ±1%. The controller’s operating frequency can be selected by a single external resistor. For applications that require stringent constant-frequency operation, a PLL (phase lock loop) allows the LTC3770 to be synchronized to an external clock, which helps reduce EMI. In normal operation, the top MOSFET is turned on for a fixed interval determined by a one-shot timer. When the top MOSFET is turned off, the bottom MOSFET is turned on until the current comparator ICMP trips, restarting the one-shot timer and initiating the next cycle, refer to Figure 2. Inductor current is determined by sensing the voltage between the SENSE+ (PGND on the SSOP package) and SENSE(SW on the SSOP) pins using a sense resistor or the bottom MOSFET on-resistance. The voltage on the ITH pin sets the comparator threshold corresponding to inductor valley current. The error amplifier EA adjusts this voltage by comparing the feedback signal VFB from a reference voltage set by the VREFIN pin. If the load current increases, it causes a drop in the feedback voltage relative to the reference. The ITH voltage then rises until the average inductor current again matches the load current. P14 E D N P O W E R T E C H N O L O G Y • N O V E M B E R 2 0 0 5

At low load currents, the inductor current can drop to zero and become negative. This is detected by the current reversal comparator IREV which then shuts off M2, resulting in discontinuous operation. Both switches will remain off with the output capacitor supplying the load until the ITH voltage rises above the zero current level (0.75V) to initiate another cycle. Discontinuous mode operation is disabled by comparator F when the PFB pin is brought below 0.6V, forcing continuous synchronous operation. The operating frequency is determined implicitly by the top MOSFET on-time and the duty cycle required to maintain regulation. The one-shot timer generates an on-time that is proportional to the ideal duty cycle, thus holding the frequency approximately constant with changes in VIN. The nominal frequency can be adjusted with an external resistor RON. Over-voltage and under-voltage comparators OV and UV pull the PGOOD output low if the output feedback voltage exits a ±10% window around the regulation point after the internal 25µs power bad mask timer expires. Furthermore, in an over-voltage condition, M1 is turned off and M2 is turned on immediately and held on until the over-voltage condition clears. Foldback current limiting is provided if the output is shorted to ground. As VFB drops, the buffered current threshold voltage ITHB is pulled down and clamped to 0.9V. This reduces the inductor valley

(“New IC’s Simplify” continued on P32)

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AC Powering Semiconductor Growth 8 by LINNEA BRUSH mbedded power is used in a wide range of distributed power architectures with much of the design focus going to the dc output side. Challenges on the ac input side are equally demanding, however, including power factor correction (PFC), hot swappability, and pulse width modulation (PWM). Semiconductor companies are providing products for this side of the house that range from digital PWM (DPWM) to OCC (one cycle control) for PFC. PFC (power factor correction) is gaining attention as new harmonic emission standards become mandatory in Europe and Japan. Other countries are at various stages in accepting these standards which means power supplies could be subject to more stringent requirements. High minimum power factors are no longer limited to high-power applications, for instance. Newer norms and standards apply to products dissipating as little as 75W or 26W for lighting devices. Low PF results in poor electrical efficiency creating the need for larger generators, transformers and other distribution devices that would otherwise not be necessary. Other PF conditions include overloads, voltage distortions, noise, parasitic harmonics in the network, and reciprocal interference in the system. Analog-based PFC control methods have long been used in power supplies. One PFC control method Figure 1: International Rectifier’s IR1150 family of gaining in popµPFC™ ICs for ac/dc power factor correction circuits ularity is to use an analog controller with a discontinuous conduction mode, such as Fairchild Semiconductor’s FAN7527B

P16 E D N P O W E R T E C H N O L O G Y • N O V E M B E R 2 0 0 5

and FAN4812. The company also introduced its new FSAB20PH60 PFC smart power module which implements the partial PFC switching converter circuit topology, switching at twice the line frequency of the traditional PFC topology. The partial-switching method is popular for 1kW to 3kW air conditioners. International Rectifier introduced the IR1150 family of µPFC™ integrated circuits for ac-dc PFC circuits. IR utilizes its licensed OCC approach in the IR1150 to deliver the performance of continuous conduction mode (CCM) PFC with the simplicity, reliability, and low component count of a discontinuous current mode circuit for PFC applications. The company Figure 2: The GPTC110X series claims that the patented OCC from Green Power technique “radically alters tradiTechnologies controls PFC stages operating tional thinking about PFC soluunder continuous tions. It’s a form of CCM PFC conduction mode using a new ‘integrator with reset’ conditions control block.” Companies are also looking at full digital power factor correction, although these solutions can have higher costs associated with them. Fairchild offers an approach that features a control method based on a modified sinusoidal pulse width modulation. Fairchild’s proposed method does not need to sense a line current or voltage, and can be implemented by using one of their low-speed and low-priced conventional microcontrollers. Power Factor One Inc. uses its patented control methods including constant pulse proportional current, analog reset system, start enforcer and nonlinearity correction to significantly simplify the converter’s circuit and improve the controller’s performance. The company states that their PF484x PWM controller circuits include near-unity PFC circuits that meet all international standards for electronic

PART FO U R: EM BED D ED POWER A SPECIAL S U P P L E M E N T TO

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topology uses three FET PFC boost ballast and off-line power converswitches and tolerates a wide input sion applications. range. Fault detection and control is A modular approach for PFC is monitored by a microprocessor. The provided by Green Power Techgeneration of the control reference nologies Ltd. The company claims for PFC correction is handled both that their plug-and-play products on an analog level and a microenable quick and easy integration of processor level. critical components into OEM prodZilker Labs has introduced the ucts with a resulting minimal bill of materials that reduces costs. The Figure 3: ON Semiconductor’s NCP1603 ZL2005, a mixed-signal, power manGPTC110X series is designed to con- combines a PFC controller chip and a agement and digital PWM IC that PWM control chip in a single, 16-pin integrates a compact, efficient buck trol the PFC stages operating under SOIC package controller, high-current adaptive continuous conduction mode conditions. It provides near-unity power factor for a univer- drivers and full power and thermal management sal input line (85Vac-265Vac) with no need for sens- functions in a single package, eliminating the need ing the input voltage. GPT is also finalizing develop- for complicated power supply manager chips and ment of a digital power management module that numerous discrete components. Digital PWM control is also being slowly introincorporates a PFC stage which is expected to be duced as a way of enabling high-frequency PWM commercially available within the next year. A new PFC/PWM controller from ON converter applications. Texas Instruments introduced Semiconductor with integrated standby and high- the UCD9501 high resolution DPWM controller voltage start-up capabilities. The NCP1603 combines which is part of its Fusion Digital Power™ family of a PFC controller chip and a PWM control chip in a products and can achieve up to 150 picoseconds single, 16-pin SOIC package. Under light load condi- DPWM resolution. Silicon Labs debuted the Si8250 DK, a developtions the NCP1603 PWM controller disables the PFC ment kit that includes tools for designing digital power function saving in the range of 200mW of power. Another company looking at digital implementa- supply controllers. The kit includes a digital power tion is C&D Technologies. They recently presented a supply and PMBus™ adapter along with software paper at the Digital Power Forum that introduced a that the designer uses to describe the desired funcdigital/analog power-controlled 5500W rectifier with tions of the controller. The code is synthesized, comthree-phase ac input and high power factor. The piled, then put into the chip. Companies like Roal Electronics are looking at front-end power supplies with combined digital and analog control. The company has a single output digital power front end with a patent-pending multiphase digital PFC. A single 8-bit microcontroller is used to manage the PFC, VBULK regulation, alarms and signal monitoring. An interleaved two-transistor forward converter PWM control is achieved by using a standard, low-cost, 10-pin analog IC with direct digital integration for power management. Ac powering may not be the primary focus of many power supply design engineers, but the demands of distributed power architectures will make it a challenging area in the next few years. As regulations change, and as digital power moves into the commercial mainstream, opportunities will emerge for power supply manufacturers to increase efficienFigure 4: The Si8250DK is a development kit from Silicon Labs that includes tools for designing digital power supply controllers cy and reduce costs. ■

N O V E M B E R 2 0 0 5 • E D N P O W E R T E C H N O L O G Y P 17

CASE Study

Scalable Power Systems Meet the Needs of Configurable Blade Servers 8 by STEVE MAPPUS, TEXAS INSTRUMENTS dc power supply, or two if redundancy or load sharing is required, and its own cooling source. Consequently, a fully-configured 42, Blade server computing systems must be highly configurable to 1U rackmount server can house as many as meet a variety of application needs. As a result, blade servers 84 individual power supplies. are bought and sold primarily based upon a desired amount of Blade servers are mounted vertically processing power required to meet the needs of a specific task. into a 3U rack unit. Ironically, one of the least considered, and yet most important, Each blade is really CUSTOMER components of a blade server is the power supply. After all, it nothing more than a sin- PROFILE can be easily argued that a system’s reliability is only as good gle board computer A LEADING as the power supplied to it. MANUFACTURER complete with memory, OF CONFIGURABLE Texas Instruments recently worked with a customer wanting processor, and network BLADE SERVER to design a 1.5kW, highly-efficient, isolated power converter module for a blade server application. This customer relies heavconnections. By sliding COMPUTING SYSTEMS ily upon a well-known power module supplier for meeting his the blades into a compower needs. Power converter modules offer many advantages, mon vertical enclosure, a larger number of but the foremost must be ease of implementation. However, servers can fit into a smaller allowable space there are several disadvantages with this approach, particularly resulting in higher computing power density in blade server applications. Server systems are designed to be compared to horizontal rackmount servers. highly-configurable in terms of available processing power. To As many as 250 blades can be installed into handle a variety of scalable power requirements, a configurable a single PCI based industry standard rack. server needs to be optimally matched to a compatible power sysUnlike the 1U horizontal rackmount tem. As a primary obligation, the customer desired more flexibilservers, dc power in a blade server is distribity by closely matching their power needs and processor requireuted from one or more power supply modments. Secondly, because of specific supervisory and power management requirements, the power modules themselves do ules through the PCI cabinet and to each of not make up a complete “power system”. And finally, the custhe individual blades. Distributing dc power tomer emphasized the need to reduce overall power system means that the ac to dc isolation only has to costs. Faced with a certain cost increase associated with outoccur once through an intermediate bus sourcing a custom power converter design for their blade server converter. Since the blades themselves do applications, this customer boldly decided to do the unthinknot have an on-board isolated power supply able– design his own custom power supply. or fan, bus power and cooling distribution can be thought of as shared system resources. Blade server power supply modules can now be paralleled and hot-swapped for greater system flexibility and scalability. In their earliest development, blades contained Traditionally, configurable servers have been built only a single processor so power dissipation was not a based upon an industry standard rack capable of hold- serious issue. However, the current trend is to pack as ing up to 42, 1U (1.75 inches) servers. Since ac power many as four power-hungry processors onto a single is bused through the server rack, each horizontally- blade which greatly increases cooling demands. And, mounted 1U server module requires one isolated ac to because the blades themselves are now dissipating so

the challenge

the solution

P18 E D N P O W E R T E C H N O L O G Y • N O V E M B E R 2 0 0 5

PART F O U R: EM BED D ED POWER A SPECIAL S U P P L E M E N T TO

much additional power, there is an ever-increasing shift (or phase overlap) that is controlled. For a comparable component count, the PSFB offers ZVS, EMI and demand to push for higher power supply efficiency. Because the customer specializes in high-per- performance benefits unmatched against the traditionformance computing systems with little to no previous al hard-switched full bridge technique. power supply design experience, designing an application specific, custom power supply was a significant challenge. TI worked closely with the customer to first understand their immediate power requirements. The 1.5kW converter needed to operate from an off-line power factor correction (PFC) regulated boost converter. Initially, the UCC38500 combination PFC/pulse width modulation (PWM) controller was considered, however this approach was eliminated because it was limited to several hundred watts of power. A version of the full-bridge power topology was really the only practical choice and for maintaining absolute highest efficiency the UCC3895 phase shifted full bridge (PSFB) PWM controller was chosen along with a Don’t let multiple source voltage designs slow you down! From SMT UCC3817 PFC boost prepoint-of-load converters, to multi-phase VRMs and bus converters regulator. The PSFB control for intermediate bus architecture, Bel has your DC/DC converter technique differs from the modules in stock, and in volume! Our full lines are traditional PWM full bridge in engineered to optimize PCB space (8A in two ways. First, an intention0.2” x 0.2” footprint) and thermal performal delay time is introduced ance (up to 94% efficiency) in 2.5V to where, under the right oper48V, and 1A to 200A applications. Offered in low-profile and SIP packages, ating conditions, zero voltage our POL, step down, non-isolated, and switching (ZVS) occurs 07CR Series of 1/8 boost converters provide the features which would be essential for Brick Bus Converters today’s networking, computing and meeting the customers need telecom designs demand. Regardless of for high efficiency. Secondly, your requirements, Bel gets competitively the duty cycle of each pripriced products to market faster. mary bridge MOSFET is fixed at 50 percent, so instead of the pulse width being control Tel:800/235-3873 Selector modulated it is the phase www.belpower.com Guide Available

DC/DC CONVERTERS

Modules for 2.5V to 48V Applications Speed Time-to-Market

E D N P O W E R T E C H N O L O G Y P 19

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PART F O U R: EM BED D ED POWER A SPECIAL S U P P L E M E N T TO

EDN

nonlinear elements are defined, the ZVS critical timing must be precisely adjusted to fully realize the converters’ efficiency benefits. Leveraging TI’s expertise in ZVS power topologies, the burden of climbing an otherwise steep learning curve was avoided. Throughout the entire development cycle, TI provided extensive design support with specification and design reviews, component recommendations and support of initial hardware debugging. Within nine months, the customer had its first “in-house” custom designed power system ramping into production. A short time later, this customer again consulted TI to discuss their specifications for a 200W dc to dc converter design. Since favorable results with the 1.5kW PSFB design had been achieved, With Every Spellman the customer naturally conBertan brand High Voltage Supply sidered using a scaled-down you get something extra inside: 200W version. The PSFB The “Know How” of the High Voltage People. would undoubtedly meet their For more than 50 years, Spellman is the innovator of the High Voltage industry. With our requirements of high efficienrecent acquisition of the respected Bertan High Voltage brand, we offer the world’s most cy and reduced cost, but was comprehensive line of generators, rack instruments, modules and Monoblock X-Ray Sources®. it the best choice? The singleended forward converter with APPLICATION KNOW HOW: Whether your field is X-Ray Analysis, Semiconductor Processing, active clamp transformer Security Detection, Medical Imaging, Electron Microscopy, or Mass reset offers many of the same Spectrometry, we make a high voltage supply to meet your needs. advantages found in the ENGINEERING KNOW HOW: PSFB topology, but at reWe have the largest engineering team in the business and one of the duced power levels. Where most innovative design libraries in our industry. the PSFB can be designed to MANUFACTURING KNOW HOW: operate at tens or even hunWe maintain world-class ISO9001 production facilities in the US, dreds of kilowatts, the active Europe and in Mexico. clamp forward is limited, in a The High Voltage People of Spellman: responsive, professional and situated globally to support practical sense, to about your high voltage needs. For more information, call us or visit our website www.spellmanhv.com 400W. Once the performance and cost trade-offs were pre475 Wireless Blvd. Hauppauge, NY 11788 sented, the customer agreed tel: +1-631-630-3000 to proceed with an active fax: +1-631-435-1620 Optimizing the converter for high efficiency depends upon a thorough understanding of parasitic circuit elements, such as MOSFET junction capacitance and transformer leakage inductance. Even once these

e-mail: [email protected]

www.spellmanhv.com

USA

EUROPE

JAPAN

MEXICO

CHINA

(“Scalable Power” continued on P33)

MONOBLOCK® is a registered trademark of Spellman High Voltage Electronics Corp.

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P20 E D N P O W E R T E C H N O L O G Y

Intersil Switching Regulators Intersil High Performance Analog

Running Out Of Room? We Suggest Fewer Chips. Reduce your board size and increase efficiency with Intersil's multiple output DC/DC Switching Regulators. Get up to 20A of output current and four regulated outputs from a single VIN ranging from 3.3V to 24V.

Design has never been so easy, with a variety of combinations of linears and PWMs, Most devices are available in thin scale packages to maximize real estate.

Intersil's Family of Multiple Output DC-DC Solutions

# of Outputs

Device

Regulators PWMs

Regulators Linears

4

ISL6521

1

3

ISL6455 ISL6455A ISL6537 ISL6532A ISL6441 ISL6443

2

ISL6227 ISL6440 ISL6539 ISL6530/1 ISL6528 ISL6529

VIN (V)

IOUT (max) (A)

Package

3

5

20

SOIC-16

1 1 2 1 2 2

2 2 2 + Ref 2 1 1

3.3 5 2.5, 12 5, 12 4.5 to 24 4.5 to 24

0.6 0.6 20 20 6 10

QFN-24 QFN-24 QFN-28 QFN-28 QFN-28 QFN-28

2 2 2 2 1 1

0 0 0 Ref 1 1

4.5 to 24 4.5 to 24 5 to 15 5 3.3, 5 3.3 to 5, 12

16 10 8 1 15 15

SSOP-28 QSOP-24 SSOP-28 SOIC-24, QFN-32 SOIC-8 SOIC-14, QFN-16

Int. FETs

Datasheet, free samples, and more information available at www.intersil.com/edn

Intersil – Switching Regulators for precise power delivery. ©2005 Intersil Americas Inc. All rights reserved. The following are trademarks or services marks owned by Intersil Corporation or one of its subsidiaries, and may be registered in the USA and/or other countries: Intersil (and design) and i (and design).

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CASE Study

PFC/PWM Combo IC Enables Best Power and Board Space Efficiency in LCD TV’s 8 by RENO ROSSETTI, DIRECTOR OF THE ANALOG PRODUCT GROUP STRATEGY, FAIRCHILD SEMICONDUCTOR JUNG WON KIM, SENIOR SYSTEMS DESIGNER, PH.D., POWER SUPPLY GROUP, POWER CONVERSION TEAM, FAIRCHILD SEMICONDUCTOR

Power conservation inside the appliance In the next few years, the worldwide number of color TVs is expected to stay roughly flat while the digital TV (DTV) sub-segment will grow at a brisk 30% CAGR, reaching 94 MUs in 2009. Flat panel TV technologies come in two flavors, LCDs (58MU in 2009) and Plasma TVs (12MUs in 2009). This article focuses on LCD TVs, which comprise the largest portion of the flat panel TV market. Today, the size of DTVs is moving up steadily, with 32” LCD TVs being produced in the highest volumes, and with sizes as high as 61” being announced. As bigger TV screens consume more power and grow faster, the end result is an exponential increase in power consumption. Energy Star is a program developed by the US Environmental Protection Agency (EPA) to require energy-savings in office equipment such as computers and monitors. An Energy Star monitor automatically goes to sleep or powers down after a period of inactivity. This feature can save 60-80% of power during idle times––all you have to do to wake up the monitor is touch the keyboard or mouse. Current regulations, such as the Energy Star program requirements for TV’s, focus on

power consumption in 4 3 stand-by requiring less 3.5 5 than 1W since 7-13 7 2005. In the future, 2.5 9 the focus should shift 2 to the bigger prize: sav11 1.5 ing power in normal 13 1 operation. Already av0.5 ailable is an E-Star final 0 document prescribing Harmonic order, n=3, 5, ... to 39; 3.85/n mA/W at n>13 limits to power consumption in normal Fig.1. IEC 61000-3-2 Edition 2.2 Harmonic Current Limits operation for External Power Supplies, for example, ac adapters, and preliminary draft monic limits of various equipment classes. prescribing efficiency of computers are also Specifically, all personal computers, displays and available. Furthermore, E-Star has just begun TV receivers (Class D equipment) drawing more to tackle the issue of regulating power con- than 75W must have harmonics at or below the profile demonstrated in Figure 1. With a modern sumption in DTVs during normal operation. 40” LCD TV easily drawing 250W. This means Efficient power draw from the AC line that these TV sets shipped to Europe must comThe other aspect of power conservation is power ply. When it comes to compliance, the rest of the factor correction (PFC). PFC regulations are con- world is following Europe's lead at varying paces. cerned with the quality of the power drawn from Figure 1 illustrates one aspect of the the line. Optimum conditions for power delivery European specification. Notice that the allowance from the ac line are achieved when the electric grows stricter for the higher harmonics; however, load, a TV set for example, draws current which these harmonics also have less energy content is in phase with the input voltage (ac line), and and are easier to filter. According to the specifiwhen such a current is undistorted (sinusoidal). cation, the allowed harmonic current maxes out To this end, IEC 6100-3-2 Edition 2.2 is the above 600W, making it more challenging to current European standard specifying the har- achieve compliance at higher power.

the solution A major TV manufacturer asked Fairchild Semiconductor, to help them design the power supply system for a 40” digital TV set. The challenge was to design a power supply system that was small and highly efficient––both constraints being dictated by the appliances thin form factor. The power supply

P22 E D N P O W E R T E C H N O L O G Y • N O V E M B E R 2 0 0 5

Harmonic current per Watt, mA/W

the challenge

system had to have efficiency above 85% in normal opera- CUSTOMER tion and meet the Energy Star PROFILE requirement of <1W power A LARGE MANUFACTURER consumption in stand-by. OF LCD TV SETS A typical 40” LCD TV set needs several AC-DC isolated outputs converting power from the 90~254Vac line. Typically, Output 1

PART F O U R: EM BED D ED POWER A SPECIAL S U P P L E M E N T TO

(24V/8A, 192W) will power the LCD back light inverter block, Output 2 (5V/0.5A) will power the logic block, Output 3 (5V/2A) will power the tuner block and Output 4 (12V/3A) will power the audio amplifier block. This adds up to a total power of 243W in normal operation with a standby power of less than 1W. The strategy we adopted to meet both normal and stand-by operation was to divide the entire system into two sub-systems, a main power supply sub-system for normal operation and an auxiliary one for stand-by (Figure 2).

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current in the storage capacitor between the PFC and PWM sections. This results in higher efficiency and smaller component size. Thanks to these features, the measured total efficiency at 85Vac was over 85%,

Stand-by Operation In stand-by mode, the main power is disconnected from the ac line. We used a relay and only the stand-by power supply built around Fairchild’s FSDM311 SMPS power switch to power the logic block. The FSDM311 consumes very little power thanks to its high-voltage start-up switch and the advanced burst mode operation to reduce switching loss.

Normal Operation In normal operation, the device’s main power supply was built around Fairchild’s FAN4800 PFC/PWM monolithic combo controller IC, which achieves high efficiency using ZVS (zero voltage switch) ASHB (asymmetric half bridge) topology and utilizes the FAN7382 for high side MOSFET drive. The patented Leading-Edge Modulation (LEM) PFC/TEM Trailing-Edge Modulation (TEM) PWM synchronization method reduces ripple

E D N P O W E R T E C H N O L O G Y P 23

The quickest way to find the power you need. Sometimes looking for the right power supply can be a hassle. That’s why Norvell has developed Power Supply Solutions. This unique tool will respond to your specifications quickly by accessing several manufactures and providing multiple power solutions. It’s just that simple. Go to norvell.com/pss and experience Norvell’s newest www.norvell.com/pss way to service your needs. Just plug it in, order it and power up!

power up

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PART F O U R: EM BED D ED POWER A SPECIAL S U P P L E M E N T TO

FAN 4800: LCD Backlight PS

D5SB60 AC LINE

FSDM311: Stand-By PS

24V/8A

FSCQ0765: Audio PS

5V/60mA

FAN5234: DC-DC

12V/3A

5V/2A Tuner 5V/0.5A Logic

Fig. 2. 40” LCD TV Power Supply System

including the PFC section, and met the customer’s Conclusion demand. The diffusion of large-sized flat panel television sets is adding new dimensions to the challenge of power management and power conservation. Regulatory PFC The FAN4800 meets the PFC regulations thanks to its agencies have so far focused on power conservation in high-performance average current mode PFC control stand-by and are just beginning to tackle regulation of block. As an added bonus, the device’s current fed (“PFC/PWM” continued on P34) gain modulator produced excellent noise immunity.

“S” Series High Voltage DC/DC Converters

* Output Power from 1 to 10 Watts * Single Outputs to 1000Vdc * Dual Outputs to +/- 500Vdc * 1000Vdc Isolation * Input Ranges (9-36Vdc, 20-60Vdc, 36-72Vdc) * Low Profile Packages (0.8” x 1.25” x 0.52” & 1” x 2” x 0.4”) * Typical Efficiency 82% * Pricing starts at $25/1K

For more information, call American Power Design Phone 888/894-4446 , Fax 603/894-4291 Email [email protected] www.apowerdesign.com

P24 E D N P O W E R T E C H N O L O G Y • N O V E M B E R xx 2 0at0www.edn.com/info 5 Enter

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High Power Buck-Boost

97% Efficient Single Inductor Buck-Boost Controller The LTC®3780 is Linear’s latest addition to our growing family of true buck-boost regulators. This wide input voltage range, high power controller is capable of delivering efficiencies of up to 97% for a 12V, 5A output from an input voltage range of 4V to 36V. Its current mode topology and single inductor architecture enable simpler solutions than traditional SEPIC or transformer-based designs. With up to 400kHz operating frequency, compact, high power density designs are easily achieved.

▼ Features

(VOUT = 12V, ILOAD = 5A)

www.linear.com Literature: 1-800-4-LINEAR Support: 408-432-1900

100% 95%

Efficiency (%)

• VIN Above, Below or Equal to VOUT • Single Inductor 4-Switch Synchronous Operation • Selectable Low Current Operating Modes • 200kHz to 400kHz Constant Frequency Operation, Phase-Lockable • VOUT Disconnected from VIN During Shutdown • 24-lead SSOP and 5mm x 5mm QFN-32

▼ Info & Online Store

LTC3780 Efficiency vs SEPIC

LTC3780

90% 85%

SEPIC Converter

80% 75% 70% 5

10

15

20

25

VIN(V)

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30

35 , LTC and LT are registered trademarks and SwitcherCAD is a trademark of Linear Technology Corporation. All other trademarks are the property of their respective owners.

Intersil Battery Charger ICs Intersil High Performance Analog

Unshackle Your Handheld Device From Its Cradle Intersil’s ISL6299 is a fully integrated low-cost Li-ion or Li-polymer battery charger that accepts both USB port and desktop cradle charger. The ISL6299 is a low component count solution that features programmable cradle charge current, charge indication, adapter present indication, and programmable end-of-charge (EOC) current with latch. All these advanced features, along with Intersil’s Thermaguard™ technology for an added measure of thermal protection, are delivered in this single chip available in a tiny 3x3 mm DFN package. ISL6299 System ISL6299 Key Features: Cradle input. The max input voltage tolerance is 28V. Programmable charge current up to 1A and programmable end of charge current. The included end of charge latch is the default input source.

Dual-Input charger for single-cell Li-ion/ Polymer Batteries for Cradle and USB Low Component Count Integrated Pass Element

USB input. Takes input from USB port or other low voltage supply. Fixed charge current at typically 380mA. Only charges when cradle source is not connected.

Programmable end of charge optimizes end-customer applications. High input voltage tolerance protects the device when used with low cost unregulated supplies or in under input transient conditions.

Fast-charging rates of an AC adaptor for when you have access to cradle.

Fixed 380mA USB Charge Current Programmable Cradle Charge Current Charge Current Thermaguard™ for Thermal Protection 28V Maximum Voltage for the Cradle Input Charge and Adapter Presence Indicators Less than 0.5µA Leakage Current off the Battery when No Input Power Attached Programmable end-of-charge current with latch for Cradle Input No External Blocking Diode Required Pb-Free Plus Anneal Available (RoHS Compliant)

28V tolerant cradle with overvoltage protection. Sync-up and fuel-up directly from your laptop with convenient USB charger.

Intersil – Switching Regulators for precise power delivery. ©2005 Intersil Americas Inc. All rights reserved. The following are trademarks or services marks owned by Intersil Corporation or one of its subsidiaries, and may be registered in the USA and/or other countries: Intersil (and design) and i (and design).

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Datasheet, eval kit with USB interface, free samples, and more information available at www.intersil.com/edn

PART FO U R: EM BED D ED POWER A SPECIAL S U P P L E M E N T TO

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CASE Study

Which Voltage Bus is Best? 8 by LOU PECHI, POWER-ONE, INC.

the challenge To meet the design goals of the equipment, the customer needed not only to reduce the size of his new design, but also reduce the material cost while at the same time increase the functionality of the power conversion and management functions. The customer required 8 distinct voltages ranging from 0.75 Volts and up to 3.3 Volts at currents ranging from low 3.7 Amp and up to 10 Amp. Besides sequentially powering each output, in order to assure proper system operation, the rate of turn on and turn off had to be different for each output. To optimize the system power dissipation the customer was faced with the problem of choosing the right bus voltage. At low bus voltages at same overall power, the current and the associated I2R dissipation in the circuit board traces is higher, while at higher voltages due to the lower currents the dissipaFigure 1. System tion is lower. Additionally, Block Diagram converting higher inputs to the low outputs at the point of loads (POLs), the dissipation in the POL itself is higher. The dissipation in the isolated dc/dc converter that converts the 48 Volt input to the bus voltage does not change appreciably due to different isolation transformer turn ratios, with the output voltage. Thus the choice of the bus voltage needs to be made based on the best balance between the circuit board trace and the POL losses.

The POLs are not isolated and do not employ a transformer to convert the IBV to the output voltage, hence the efficiency of the device varies with the voltage differential between the input and the output. This means that the POL operates more efficiently with lower voltage differentials across the device. The printed circuit board (PCB) trace resistances are constant and the power is a multiple of voltage and the square of the current (I2R). When delivering power to a load, it is desirable to raise the distribution voltage to the highest level feasible so as to lower the current and minimize the trace voltage drops. CUSTOMER As power requirements in a system PROFILE vary, the load currents of each POL, and A LEADING thus the total IBV current varies, affectDEVELOPER OF ing the PCB trace voltage drops. NEXT-GENERATION At low power requirements the IBV OPTICAL ULTRAHIGH-SPEED can be lowered in order to reduce the TRANSMISSION voltage drops and increase the efficienTRANSPORT cy of the individual POL converters. PRODUCTS. At higher system power requirements the IBV can be increased in order to reduce the PCB current and reduce the trace (I2R) power losses. Within a range of varying system power requirements, there is an optimum IBV where the efficiency is maximized. Analysis calculations, using actual copper circuit board trace resistances, indicated that even though the power dissipation in the POLs was higher, at the high required currents, the higher bus voltage resulted in a slightly better efficiency of 80% for the 12 Volt bus vs. 78% efficiency for the 5 Volt bus.

the solution The concept is illustrated in Figure 2. The isolated dc/dc Converter is an isolation transformer used to convert the higher input voltages to a lower intermediate bus voltage (IBV), and the efficiency does not appreciably change with the voltage differentials across the device. Figure 2. Power Dissipation Block Diagram

N O V E M B E R 2 0 0 5 • E D N P O W E R T E C H N O L O G Y P 27

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PART F O U R: EM BED D ED POWER A SPECIAL S U P P L E M E N T TO

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Solution Implementation Simulation of the two intermediate bus voltages confirmed the theoretical calculations. The customer chose the Power-One QBC11ZH-NT isolated converter that met the requirements of converting the wide input worldwide telecom bus voltages of 36 to 75Vdc to a 12V bus at 11A.

the ZM7108 Digital Power Manager (DPM). The eight Point of Load Converters (Z-POLs) were programmed and managed by the eight channel ZM7108 as shown in Figure 3.

SERIES BOP HIGH POWER Figure 3. Chosen DPM and Z-POLs

For the POLs the customer had a choice to use the ZY7007 (7 Amp) and the ZY7010 (10 Amp) for the lower currents, and the ZY7115 (15 Amp) for the higher output currents. In order to minimize the number of different components, the customer chose the ZY7115 intelligent, fully programmable step-down POL converters, even though some of the output current requirements were below the capabilities of the device. Besides reducing the number of different part numbers, operating way below the rated output current capabilities of the POLs increased the overall system reliability. To manage and control the 8 POLs his choice was

POWER TOOLS

d-c bipolar power 1KW • Source & sink, 4 quadrant operation. • Fast analog programming. • Precision stabilization: 0.001% source, 0.002% load. • Digital programming. • Built-in arbitrary waveform generator.

www.kepcopower.com/bophi.htm

SERIES KLP voltage, current and power-limited operating boundaries 1200 watts • GPIB, RS 232 & isolated analog control standard. • True 1U height - full power operation with no spacing between units. • Wide range a-c input with active PFC.

www.kepcopower.com/klp.htm

SERIES RTW d-c modular power 50-100 watts

Kepco, Inc., an ISO 9001 company, has been making precision-stabilized power supplies since 1946. We specialize in analog-controlled fast-programmable d-c products, capable of producing 1, 2 or 4- quadrant (bipolar) outputs. Digital control is supported under GPIB (IEEE 488.2), RS232 and VXI, using SCPI and CIIL. VXI plug&play capability is available for more than 50 models ranging up to 1200 watts. Kepco also offers industrial and OEM modular power supplies in single and multioutput designs. Many designs current share for hot-swap and N+1 redundancy applications. We take pride in the new and innovative power products that will further expand the horizon of options for systems designers. For the tools you can rely on, from a company you can trust, call Kepco today or check out our Web site.

RoHS Compliant

• Wide range a-c input with active PFC. • Low profile, optional cover factory installed. • FCC Class B conducted and radiated emissions.

www.kepcopower.com/rtw.htm

E D N P O W E R T E C H N O L O G Y P 29

You need to use the right tools to get the job done. Kepco provides you with these tools in our broad line of instrumentation and modular power supplies.

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131-38 Sanford Avenue, Flushing, NY 11352 USA Tel: (718) 461-7000 • Fax: (718) 767-1102 Email: [email protected] VISIT OUR WEB SITE FOR MORE INFO

www.kepcopower.com

PART F O U R: EM BED D ED POWER A SPECIAL S U P P L E M E N T TO

GAIA-CONVERTER GAIA

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Figure 5. Turn on Simulation

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Figure 6. 50% Load Transient Simulation

The DPM bi-directionally communicates with the 8 ZOne POLs and with the main system through a standard two wire I2C Bus. The DPM, besides communicating with the main system, can set through a graphical user interface (GUI) I2C interface each Z-POL converter’s parameters such as, output voltage, sequencing, tracking, protection type and thresholds, frequency, fault propagation, interleave and feedback loop compensation. The DPM constantly monitors each Z-POL converter’s output voltage, current and temperature, while the Z-POLs monitor and report their individual status of, over and under voltage protection (OVP & UVP), and power good high and low (PGH & PGL). Data, such as output voltage, output current, and temperature, are constantly updated and stored in the DPM’s shift register and can be accessed in case of system failure. Such telemetry data can also be used to monitor the temperature at each POL location. Fault management between the Z-POL converters can be programmed to act differently when faults occur. If no fault propagation is required, the protection, depending on fault severity, shuts down just the faulty Z-POL in a latching or non-latching mode (hiccup with a 130ms period). Fault propagation within a group of Z-POLs, besides shutting down the failed Z-POL, shuts down all the Z-POLs within the group and assures that the group is synchronously turned

(“Which Voltage Bus is Best?” continued on P34)

P30 xx E DatN www.edn.com/info POWER TECHNOLOGY • NOVEMBER 2005 Enter

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(“New ICs Simplify” continued from P14) current level to one tenth of its maximum value as VFB approaches 0V. Foldback current limiting is disabled at start-up. Margining is a resistor-programmable function with the LTC3770. A resistor placed between the programmable margining input pin and ground sets the margining current. This current multiplied by the resistor between the VREFOUT and VREFIN pins sets, determines the margining voltage offset. In addition, the MSB and LSB logic inputs for the margining function together determine whether the IC is in margin high, margin low, or no margin state. This functional capability is particularly useful for designs who need

to stress their systems by varying supply voltage during testing. The LTC3770 has the ability to either soft start by itself with a capacitor or track the output of another supply. When the device is configured to soft start by itself, a capacitor is connected to the TRACK/SS pin. The LTC3770 is put in a low quiescent current shutdown state if the RUN pin voltage is below 1.5V. The TRACK/SS pin is actively pulled to ground in the shutdown state. Once the RUN pin voltage is above 1.5V, the LTC3770 is powered up. A soft-start current of 1.4µA then starts to charge the soft-start capacitor CSS. Pin Z1 must be grounded for soft-start operation. When the device is configured to track another supply, the feedback voltage of the other supply is duplicated by a resistor divider and applied to the TRACK/SS pin. In this case, Pin Z1 should be tied to INTVCC to turn off the softstart current in this mode. Therefore, the voltage ramp rate on this pin is determined by the ramp rate of the other supply output voltage.

Summary Designers of POL dc/dc converters for embedded systems face many challenges due to the multiple constraints of limited space and cooling within a given enclosure, as well as the need for the correct power supply tracking for improved system reliability. Despite having to navigate through this myriad of constraints, the recently introduced LTC3770, from Linear Technology provides a simple, compact, efficient and feature rich solution.■ Figure 2. Functional block diagram of the LTC3770 (QFN package)

P32 E D N P O W E R T E C H N O L O G Y • N O V E M B E R 2 0 0 5

PART FO U R: EM BED D ED POWER A SPECIAL S U P P L E M E N T TO

(“Embedded Power” continued from P10) feedback loop compensation and configuration. Astec's DTX provides up to 50W of power from a 36V to 75V input and offers outputs ranging from 0.96V to 1.44V. While each company uses the same PMBus "language" to set parameters, the software used can vary substantially. Delta Electronics in conjunction with Primarion, a PMBus adopter, announced Delta's Digital X-Power 30 (DXP30), which uses Primarion's digital multiphase PWM controller. The DXP 30 delivers 30A, with an input voltage range of 7V to 11V and provides adjustable output voltage from 0.8V to 2.5V in digitally defined steps of 1.62 mV. While more digital products are coming to market, the market is still working out which solutions, if any, are best. Another perceived difference between PMBus implementations and Power-One's approach is the open-standard vs. proprietary design debate. However, both sides fit on both sides of the debate. Power-One formed the Z-Alliance with C&D Technologies and Atmel in order to secure second sourcing for the Z-One Digital IBA products so it is no longer a single-source product. While the PMBus is

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an open communications standard, the products that use this standard are not necessarily going to be compatible in terms of size or pin outs. So even though PMBus products speak the same language, they are not necessarily the same. While the above discussion focuses on the supply side of digital power control and digital power management, the demand side is beginning to show signs of life, as well. Large OEMs including IBM and EMC have expressed increasing interest in using digital power technologies, with a few caveats. The first caveat high on the list is price parity. Several OEMs have indicated that once digital solutions reach price parity, more specifically, acquisition cost price parity with analog solutions, digital power solutions will be implemented. Secondly, OEMs have indicated that they need to be more involved in the design process of digital power solutions rather than simply being left to choose either a PMBus- or Z-Alliance-based solution. While digital power developments are dominating the power news, the combination of growing markets for the IBA, PoE and digital power will drive developments for embedded power market for some time to come.■

ciation for all that is involved in custom designing efficient power conversion products for their blade server clamp forward design based upon the UCC2894 active systems. The customer has even been discussing the possibility of allocating in-house design resources clamp current mode PWM controller. To help quickly bring the customer up to speed, uniquely dedicated to developing custom power sysTI provided a reference design and a working convert- tems for blade server applications. er used as a learning aid for gaining a thorough understanding of active clamp forward converter principles. Summary TI also delivered a custom-designed mathematical • A 1.5kW PSFB power supply with PFC was model to predict the power converter module efficiendesigned using the UCC3817 PFC boost pre-regucy. Efficiency modeling is useful because it speeds up lator and UCC3895 Advanced Phase Shift PWM the design verification process by allowing exploration controller. of the effects on efficiency while varying design com- • Using the UCC2894 active clamp current mode ponents or operating parameters. With TI’s design supPWM controller, a 200W dc to dc converter was port, this customer was able to take their first active designed for reduced cost and high efficiency in a clamp forward converter from concept to pre-producblade server application. tion in less than six months. • Reference designs and efficiency modeling tools The customer now has experience with two of the were provided to reduce design cycle time. most efficient power topologies available and has scal- • Customer now has two scalable ZVS power designs able power solutions from less than 100W to many to cover blade server applications from as low as kilowatts. In addition, they have acquired a real appre100W to many kilowatts.■

(“Scalable Power”continued from P20)

N O V E M B E R 2 0 0 5 • E D N P O W E R T E C H N O L O G Y P 33

PART FO U R: EM BED D ED POWER A SPECIAL S U P P L E M E N T TO

(“PFC/PWM” continued from P24)

and trailing-edge modulation in both normal operation and burst mode for stand-by, are essential ingrepower consumption in normal operation. Fortunately dients for meeting the demand to operate modern from the prospective of energy conservation, in the appliances with minimum power waste. case of LCD and Plasma TVs, the size constraints combined with the relatively high amount of heat produced Summary are pushing the demand for efficient solutions inde- • Meet the Energy Star regulations in pendently from the existence of any regulatory incenstand by mode. tives. The application of advanced architectures and • Consume a low amount of power during operation. techniques, like ZVS and a combination of leading- • Meet the PFC specifications.■

than multiple calculations and massive component changes which could have taken weeks to implement. back on. The fault propagation to the system prop- Each parameter was individually adjusted with results of such adjustments instantly displayed (Figure 4). agates the fault to all Z-POLs in the system. All performance parameters such as turn-on and The I2C connected to a PC based graphical user interface (GUI) was used to program and monitor the turn-off timing and rate (Figure 5) as well as output output voltages and currents, as well as sequence transient response to load changes (Figure 6) were and adjust the individual POL response parameters. simulated in real time and displayed on an oscilloThe use of the GUI made the programming and sim- scope connected to the system. ulation of the system very easy. Z-POL converter parameters, such as loop gain, turn-on and turn-off time and rate, Summary required only simple point-and-click adjustments rather • Having a variety of component choices from a single vendor allowed this customer to select the best solution for his system design. • Selecting the right intermediate bus voltage, the customer realized the highest overall system efficiency. • Usage of the ZY7115 vertically surface-mounted Z-POLs significantly reduced the circuit board space requirements. • System design, development, and troubleshooting were dramatically reduced. • Using the same devices for all the output voltage requirements minimized the inventory of different components. • Reduction in the number of discrete components improved the overall system reliability. • Customer met and exceeded all design and budget goals, with timely market Figure 4. GUI transfer function display introduction.■

(“Which Voltage Bus is Best?” continued from P30)

P34 E D N P O W E R T E C H N O L O G Y • N O V E M B E R 2 0 0 5

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PFC. Simplified.

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Note: Fairchild’s products are shown in red.

For more information on our PFC solutions, innovative packaging, tools, demo boards, and application notes, visit www.fairchildsemi.com/acdc/pfc1. Enter xx at www.edn.com/info

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