Adc - Dac
This document was uploaded by user and they confirmed that they have the permission to share it. If you are author or own the copyright of this book, please report to us by using this DMCA report form. Report DMCA
Overview
Download & View Adc - Dac as PDF for free.
More details
- Words: 325
- Pages: 12
ADC - DAC
A/D and D/A Conversion • Analog to Digital (A/D) Converter: converts a voltage signal to a binary encoded number that is proportional to that voltage. • Digital to Analog (D/A) Converter: converts a binary encoded number to a voltage that is proportional to that number. • We’ll assume the codes for the binary codes are signed or unsigned binary. • Many signals are easier to process via computer once they have been converted to number, i.e. digital form.
•Analog-to-Digital Converter (ADC) converts an input analog value to an output digital representation. •This digital data is processed by a microprocessor and output toa Digital-to-Analog Converter (DAC) the converts an input binary value to an output voltage.
Continuous-Time vs. Discrete-Time Signals
Vocabulary •ADC (Analog-to-Digital Converter) –converts an analog signal (voltage/current) to a digital value •DAC (Digital-to-Analog Converter) –converts a digital value to an analog value (voltage/current) •Sample period –for ADC, time between each conversion –Typically, samples are taken at a fixed rate •Vref (Reference Voltage) –analog signal varies between 0 and Vref, or between +/-Vref •Resolution –number of bits used for conversion (8 bits, 10 bits, 12 bits, 16 bits, etc). •Conversion Time –the time it takes for a analog-todigital conversion
Sampling Continuous-Time Signals
Types of D/A and A/D Converters •D/A Converters • Inverting Summer DAC • R-2R DAC • A/D Converters • Successive Approximation ADC • Flash ADC
Control logic use a counter to apply successive codes 0,1,2,3,4... to DAC (Digital-to-Analog Converter) until DAC output is greater than Vin. This is SLOW, and have to allocate the worst case time for each conversion, which is 2N clock cycles for an N-bit ADC.
Initially set VDAC to ½ Vref, then see if Vin higher or lower tan VDAC. If > ½ Vref, then next guess is between Vref and ½ Vref, else next guess is between ½ Vref and GND. Do this for each bit of the ADC. Takes N clock cycles.
Binary Weight
A/D and D/A Conversion • Analog to Digital (A/D) Converter: converts a voltage signal to a binary encoded number that is proportional to that voltage. • Digital to Analog (D/A) Converter: converts a binary encoded number to a voltage that is proportional to that number. • We’ll assume the codes for the binary codes are signed or unsigned binary. • Many signals are easier to process via computer once they have been converted to number, i.e. digital form.
•Analog-to-Digital Converter (ADC) converts an input analog value to an output digital representation. •This digital data is processed by a microprocessor and output toa Digital-to-Analog Converter (DAC) the converts an input binary value to an output voltage.
Continuous-Time vs. Discrete-Time Signals
Vocabulary •ADC (Analog-to-Digital Converter) –converts an analog signal (voltage/current) to a digital value •DAC (Digital-to-Analog Converter) –converts a digital value to an analog value (voltage/current) •Sample period –for ADC, time between each conversion –Typically, samples are taken at a fixed rate •Vref (Reference Voltage) –analog signal varies between 0 and Vref, or between +/-Vref •Resolution –number of bits used for conversion (8 bits, 10 bits, 12 bits, 16 bits, etc). •Conversion Time –the time it takes for a analog-todigital conversion
Sampling Continuous-Time Signals
Types of D/A and A/D Converters •D/A Converters • Inverting Summer DAC • R-2R DAC • A/D Converters • Successive Approximation ADC • Flash ADC
Control logic use a counter to apply successive codes 0,1,2,3,4... to DAC (Digital-to-Analog Converter) until DAC output is greater than Vin. This is SLOW, and have to allocate the worst case time for each conversion, which is 2N clock cycles for an N-bit ADC.
Initially set VDAC to ½ Vref, then see if Vin higher or lower tan VDAC. If > ½ Vref, then next guess is between Vref and ½ Vref, else next guess is between ½ Vref and GND. Do this for each bit of the ADC. Takes N clock cycles.
Binary Weight
