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Fast, ADCs for AC excitation

Lukas Salzburger
Prodigy 100 points

Other Parts Discussed in Thread: ADS1261, ADS1263, ADS1262

I am looking for a solution for measuring a resistive bridge with AC excitation and a bandwith of >50kHz. So in principle something like the ADS1261 / ADS1262 / ADS1263, but with a more than 2.5x faster sample rate. As a tradeoff I could sacrifice 2-3 ENOBs

Which TI ADCs have the „internal reference multiplexer“, or „VREF mux“ feature? Is it possible to use an external crossbar switch or would that introduce errors that would destroy the AC excitation advantages?

  • +1
    TI__Guru** 113765 points

    Hi Lukas,

    The devices you have mentioned are the precision ADCs where the device is to be used with AC excitation.  They are the fastest devices we have with that feature.  We do have faster ADCs but you would need to create a method using an external controller to control an H-bridge or FETs used for switching.

    The use cases I have seen using fast switching (even with the ADS1261) has issues with increased noise due to analog settling.  I haven't seen much value with using AC excitation at high data output rates.

    I don't know anything about your application, but an alternative to AC excitation is the use of global chopping which chops the input stage but not the reference to remove offset.  Of course this method only removes offset and not the action of self-heating of the sensor where AC excitation would be of benefit.  A would suggest taking a look a A Basic Guide to Bridge Measurements.

    Best regards,

    Bob B