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
  • 0
    •  Analog Employees 
    on Mar 24, 2013 9:32 PM

    Hi, Ravi.

    Apologies for the delayed response. Yes, if you could please send in your schematics especially on the actual connections of AD8138 and AD7934, it would be very helpful. Please also include scope shots of your output.

    I have a few notes from what you have provided. What is your VDD? From your control register values, you are using 0-2Vref range of the ADC with the internal 2.5V reference. Note that in this case, VDD must be between 4.75V to 5.25V.

    Please also note that for pseudo differential operation Vin- is typically -0.3 to 0.7V for VDD = 3V and -0.3 to 1.8V only for VDD = 5V.

    Regards,

    Karen

Reply
  • 0
    •  Analog Employees 
    on Mar 24, 2013 9:32 PM

    Hi, Ravi.

    Apologies for the delayed response. Yes, if you could please send in your schematics especially on the actual connections of AD8138 and AD7934, it would be very helpful. Please also include scope shots of your output.

    I have a few notes from what you have provided. What is your VDD? From your control register values, you are using 0-2Vref range of the ADC with the internal 2.5V reference. Note that in this case, VDD must be between 4.75V to 5.25V.

    Please also note that for pseudo differential operation Vin- is typically -0.3 to 0.7V for VDD = 3V and -0.3 to 1.8V only for VDD = 5V.

    Regards,

    Karen

Children
No Data