Selection criteria for ADC

Selection of an A/D or D/A converter depends on the requirements of the application. The main criteria are:

1. Resolution: number of bits (8, 10, 12, 16). It decides the smallest detectable change (LSB = FSR / 2^n). For example, 12 bits over 10 V gives 2.44 mV.
2. Accuracy: total error from offset, gain, INL and DNL; should be better than +/-1/2 LSB.
3. Conversion (sampling) speed: conversion time for ADC, settling time for DAC. Needed sampling rate must exceed twice the highest signal frequency (Nyquist). Flash ADC is fastest, SAR is medium, dual slope is slow but accurate.
4. Type/architecture: flash, SAR, dual slope, sigma-delta for ADC; weighted resistor, R-2R, current steering for DAC.
5. Input/output range: unipolar or bipolar, voltage or current, reference voltage (internal or external).
6. Linearity and monotonicity: DNL, INL specified; no missing codes.
7. Interface: parallel or serial (SPI/I2C), compatibility with microprocessor bus and logic levels (TTL/CMOS), tri-state outputs, built-in latches.
8. Number of channels: with or without multiplexer and sample and hold.
9. Power supply and consumption, temperature range and stability (drift).
10. Cost, package and availability.