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ADC12J4000EVM AC coupled input

Cristian Trofinenco
Prodigy 30 points

Hi,

Could you please confirm that the board modifications for differential DC/AC-coupled input on ADC12J4000JEVM as described in ADC12J4000EVM-SCH_E3.PDF are correct?

According to the schematic C1 and C2 have to be populated with 100pF capacitors and C3 and C5 removed. The Comment on the schematic says "Remove C45, C69, Populate C33=C70=100pF ". Is there a mismatch between the silkscreen and schematic?

Are there any other board changes required to change the input option?

Thank you,

Cristian

  • 0
    TI__Mastermind 44680 points

    Hi Cristian

    Unfortunately the note in the schematic is out of date as you have noticed. You are correct that C3 and C5 should be removed, and C1, C2 should be populated for differential AC coupled operation. Resistors should be used instead of capacitors if DC coupled operation is needed. When driving in DC coupled mode, the common mode voltage of the source must match the Vcmo voltage output by the ADC, and available on the Vcmo test point.

    Regards,

    Jim B