The applications provided on the datasheets of many of the Analog to Digital converters show three capacitors on the Va, Vd and Vref pins. Are all of these capacitors required?
One or two capacitor might be sufficient, depending upon the particular device and the board layout. The larger capacitor, typically 5 to 10µF, provides low impedance bulk energy storage for voltage stability during conversions and transitions. The smaller capacitors absorb any higher frequency noise spikes. If the pc board is very well laid out for low noise operation, and does not contain a microcontroller or other noisy digital logic, fewer capacitors may be required. But to obtain the guaranteed accuracy level for the ADC being used, it is generally best to follow data sheet recommendations.
