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Original question:

ADS1284: High Frequency performance at high gains

ADS1284: ADS1284: High Frequency performance at high gains

Gareth Goldswain
Prodigy 65 points
Part Number: ADS1284

Tool/software:

I previously asked a question here:  ADS1284: High Frequency performance at high gains 

I did missed the response from  who stated:

The PGA frequency response should be flat for all gains out to 1600Hz, which is the bandwidth of the FIR filter at 4ksps.  If you are bypassing the FIR and directly using the SINC filter, then you may see some attenuation at higher frequency.

What gain and filter mode are you using in this case?

To answer your question  , we are using gain=16 and FIR filter. It was not me who saw this but an end user who reported it, so unfortunately I do not have any data to show you.

  • 0
    TI__Mastermind 46380 points

    Hello Gareth,

    I do recall another customer seeing an attenuation, but they had used the wrong value filter capacitor on CAPP,CAPN pins.  We recommend a filter capacitance of 10nF; I think the customer had accidentally installed a 100nF capacitor, which did cause the input signal to be attenuated.  As long as the CAPP,CAPN value is 10nF, and a high quality film or ceramic (NP0/C0G), then you should see a very flat response when using the FIR filter.

    Regards,
    Keith Nicholas
    Precision ADC Applications