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Original question:

ADC12DL1500: Pin usage and migration guide

ADC12DL2500: IN+/- of ADC

Nandini Muralidharan
Intellectual 810 points
Part Number: ADC12DL2500
Other Parts Discussed in Thread: ADC12D1800,

Tool/software:

Hi,

We have a legacy system with ADC12D1800 whose VINI+/- and VINQ+/- were connected from LMH6554WNC as below.

Now that we are migrating to ADC12DL2500, can the same circuit be used? or should any components in this circuit be tuned?

The input to LMH is from a Digital step attenuator.

Thanks

  • 0
    TI__Mastermind 39140 points

    Hi Nandini,

    These two ADCs have different internal frontend designs at the analog inputs. Therefore, the input common mode for D1800 is +1.25V when DC coupled. The DL2500 is 0V common mode. 

    This mean you need a negative supply to the LMH amp in order for this circuit to work.

    I would suggest starting there on the amplifier interface, then we can help tune the frontend end circuit if needed.

    Regards,

    Rob

  • 0
    Intellectual 810 points

    Hi Rob,

    When you say negative supply to LMH amp, do you mean anything in addition to connecting the VCM to GND in the existing circuit?

    If yes, please share which other LMH pins you are referring to.

    Also for Analog FE tuning, can you pls support so that we can update accordingly?

    Thank you.

  • 0 in reply to Nandini Muralidharan
    TI__Mastermind 39140 points

    Hi Nandini,

    Here is what I mean. See attached. You will need to shift your power supplies on the LMH amp in order to satisfy the VCM requirements by the ADC.

    For the tuning, I can help support. But I need help understanding what you are trying to achieve. Filter type? BW?, etc.

    Regards,

    Rob