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AFE7225: AA filter requirement for ADC input

Part Number: AFE7225
Other Parts Discussed in Thread: ADS8910B,

Hi TI Team,

As per the attachment document,  For ADS8910B part there is a recommendation for AA filter Cflt and Rflt component values. But in AFE7225 IC we have not found any recommendation for ADC input AA filter.

Please suggest a suitable AA filter for AFE part or send a AA filter design document to design suitable AA filter as our requirement. 

TI_AFE.pdf

  • Hi Team,

    Any update on AA filter requirement circuit for AFE7225.

  • The anti-aliasing filter has some contingency on system parameters like signal bandwidth and SNR requirement.  The topology also has some dependence on the circuit or amplifier that is driving it.  A universal filter is not possible given those variables.

    In general, check out the design schematics here: https://www.ti.com/lit/zip/slac674.  The schematics show a shunt RCR glitch filter.  This is intended to filter out glitch energy caused by the switching capacitor in the ADC front-end sample and hold.  There is also a series 10 ohm used to further dampen the glitch energy.  It is possible to add a simple RC filter to serve as the AA filter with a corner frequency set based on the BW of your signal.  Be careful with op-amps driving the  RC filter...some devices do not "like" a highly capacitive load.  You can skew the R higher to keep the C lower to keep the op-amp "happy".

    --RJH