The purpose of the sample and hold circuitry is to take a snapshot of the sensor signal and hold the value. The ADC must have a stable signal in order to accurately perform a conversion. An equivalent circuit for the sample and hold is shown in Figure 44. The switch connects the capacitor to the signal conditioning circuit once every sample period. The capacitor then holds the voltage value measured until a new sample is acquired. Many times, the sample and hold circuitry is incorporated into the same integrated circuit package.
Figure 44: Equivalent Circuit for a Sample and Hold
