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About combination about ADC12040 and LMH5660

Satoshi
Guru 19585 points
Other Parts Discussed in Thread: ADC12040, LMH6550

Please let me know about ADC12040's datasheet P18.

Customer planning,

・ADC12040 input is "Vin+/Vin-：2.5V"

・LMH6550 output is "Vin+/Vin-：2.0V"

Is it no ploblem?

Or, Are input and output necessarry to set the same voltage?

※Customer based on these circuit. 　

   LMH6550's VCM:2.0V (by Figure22)

 

Best regards,

Satoshi

  • 0
    TI__Expert 4340 points

    Satoshi

    If the interface between the LMH and ADC is AC coupled, then matching the common-modes is not required. If the customer would like to DC couple the interface, then common-mode matching is required. The ADC requires an input common mode of 2.5V. The output common mode of the LMH is configurable by biasing the VCM pin. This can be biased using a high accuracy resistive voltage divider on the +5V ADC supply so that the LMH output common mode tracks the ADC supply. 2.5V appears to be safely within the support output common-mode range of the LMH, so the application should work OK. It may be that the 2.5V common-mode voltage limits the output swing of the LMH, but the performance reported in the +5V electrical table section (not the +/-5V section) should accurately show the performance in the customer's use-case.

    Regards, Josh