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AFE58JD16: Using ADC in DC coupled mode or Alternative Part Suggestions

Jake Zimmer
Prodigy 20 points
Part Number: AFE58JD16
Other Parts Discussed in Thread: ADS9817

Tool/software:

Hi E2E Forum,

We're wondering if the AFE58JD16 supports DC coupled input. It appears perfect for our use case except for the AC coupled inputs. Is it possible to use this part in DC coupled mode?

Our product requires 128 differential 14/16-bit ADC channels to sample at least 200kHz signals (higher speed oversampling is a bonus). The integrated 3rd order low pass filtering in this part greatly simplifies our design. If this part does not allow DC coupled inputs, are there other ADCs from TI or other separate analog front ends that offer compact multi-channel signal conditioning for analog to digital converters that would be recommended? We are fairly space constrained and so having integrated multi-channel blocks are very advantageous.

Any advice or input would be greatly appreciated. Thanks!

  • 0
    TI__Expert 7725 points

    Hi,

    AFE58JD16 and other AFE in this family is designed to give input with AC coupling . And low freq noise is also higher in these parts. 

    However you can use AD52j90/91 with DC coupling .Please take a look at this part. 

    What is the ADC sampling speed you are looking at ? With the above description I understood your input is around 200KHz. Is that correct ? 

     

    ADS9817 is from different group which gives 8 channel 8MSPS ADC. You can raise another e2e post asking for details .

  • 0 in reply to Sachin H K
    Prodigy 20 points

    Hi Sachin,

    Thanks for your response. The AD52J90 looks interesting as does the ADS981* series.

    Our maximum input frequency is around 200KHz, that is correct.

    After looking at it again, we can probably accommodate the AC coupling of the AFE58JD16 but need differential inputs. I see that the LNA has a capacitor to ground on it's negative input internally but is there anything else preventing it from being used as a differential input?

    Thanks,

    Jake

  • 0 in reply to Jake Zimmer
    TI__Expert 7725 points

    Hi,

    Unfortunately AFE58JD16 does not support differential input. Internally INM bypass capacitor are used to realize HPF corner . Also if you give signal on inm pin LNA common mode is going to change and it is not designed to handle that .

    You can use differential to single ended converter before using AFE58JD16 . Do you see any constraint for that ?