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ADS1263: how get Vin +-5V with +5V external reference

Xu Junhua
Prodigy 90 points
Part Number: ADS1263
Other Parts Discussed in Thread: THS4131

Hi,

if I use +5V external reference, to measure +-5V pesudo difference singnal，how to design the circuit?

Thanks,

Junhua

  • 0
    TI__Mastermind 44720 points

    Hi Junhua,

    In order to measure a +/- 5V differential signal with the ADS1263, the signal will need to be fully-differential. In other words, the input signals must mirror each other around a mid-supply common-mode voltage. For example, if the ADS1263 is operated off of a unipolar 5V supply then:

    +5V differential input requires: AINP = 5V, AINN = 0V
    -5V differential input requires: AINP = 0V, AINN = 5V

    You might consider using a fully-differential amplifier to convert the pseudo-differential signal to a fully-differential signal, as shown below:

    The main problem with the above circuit, is that the output becomes nonlinear near the supply rails. Therefore, you may need to support a wider supply range and use a similar circuit with a higher voltage amplifier, such as the THS4131.

    Best Regards,
    Chris

  • 0 in reply to Christopher Hall
    TI__Mastermind 44720 points
    Hi Junhua,

    I received a notification of a follow-up question, but I don't see the question posted here... Did you find the answer you were looking for?

    For clarification, the ADS1263 can accept a +/-5V differential signal when a 5V external reference voltage is applied; however, no input signal should exceed the supply voltages. Therefore, you would not be able to directly measure a single-ended signal that swings between -5 and +5V (10V differential), without first attenuating it. If you're analog supply is not bipolar, then you would also need to level shift the signal.

    Best Regards,
    Chris