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When ad7321 collects voltage, a spike voltage appears

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Malugu

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When AD7321BRUZ collects voltage, a spike voltage appears at the input every time it is acquired.

After the input is opened, the ripple voltage is shown in the following figure:

11.png

12.png

Can you explain this situation.
 

KlausST

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Hi,

please use the link to the manufacturer internet site. There you get the latest and most reliable informations.

Spike:
This is caused by the "track and hold" capacitor and is quite usual for a SAR ADC.
Thus often a buffer OPAMP is recommended.
Read the datasheet "Track-and-Hold Section"

Klaus
 

FvM

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You don't show what's connected to VIN0 and VIN1. The ADC inputs are usually driven by a low impedance buffer, otherwise charge injection of the sampling switches will be observed.
 

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