AD7934 full-differential mode

Dear All,

I'm using AD7934 with FPGA interface. I want to use AD7934 in differential mode.

I've used AD8138 for converting single-end to differential signal.

ADC is working in single-end mode (M0=0,M1=0) quite nicely. I tried all four input channels VIN0-3 in single mode all are working nice.

But When I configure ADC  for fully diferential and even pseudo differential mode but no success. Output keeps fluctuating.

Kindly help me

Thanx in advance

Parents
  • Thanx for reply,

    Following way I've connected AD8138 (ADC driver) to AD7934.

    pin-4(AD8138) connected to pin-25 (AD7934)

    pin-5(AD8138) connected to pin-26 (AD7934)

    When I checked signal between VIN0-VIN1 of AD7934 it is coming as expected diffential

    for sinewave input. Then I applied 2V DC at pin-1 of AD8138 and 2.5V on pin-2(VOCM of AD8138). I observed around 0.5V voltage between VIN0-VIN1.

    I tried following Control register value : 309h,109h,129h and so many different combinations.

    But the result is fluctuating continuously even for DC input.

    please help

    Waiting for reply

Reply
  • Thanx for reply,

    Following way I've connected AD8138 (ADC driver) to AD7934.

    pin-4(AD8138) connected to pin-25 (AD7934)

    pin-5(AD8138) connected to pin-26 (AD7934)

    When I checked signal between VIN0-VIN1 of AD7934 it is coming as expected diffential

    for sinewave input. Then I applied 2V DC at pin-1 of AD8138 and 2.5V on pin-2(VOCM of AD8138). I observed around 0.5V voltage between VIN0-VIN1.

    I tried following Control register value : 309h,109h,129h and so many different combinations.

    But the result is fluctuating continuously even for DC input.

    please help

    Waiting for reply

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