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Dual LTC6373 (in series) driving AD4134 channel

Category: Hardware
Product Number: LTC6373

Hi experts,

We are designing a data acquisition system with multiple wide-range analog inputs into several AD4134 ADCs (16 channels in all).

We are considering the LTC6373 as front-end PGA and ADC driver but we need more than X16 gain as we need to cover ranges of +-10V to +-20mV.

Is there any reason why we can't use two LTC6373s in series to give use a X256 gain?

Thanks, Steve

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  • Hi Steve,

    +-10V to +-20mV.

    Do you mean 10mV?

    So far looking at the input and output wing, looks like 2 cascaded LT6373 would work as G=256 for AD4131. Although our usual configuration composes of Gain Amplifier > Driver (signal conditioning) > ADC. Trade offs that I would want to watch is noise and BW. As you gain the first stage amplifier, we're also gonna gain up the noise. We need to make sure that the ADC noise is still the dominating noise. 

    I'm also wondering, do you have a specific reason why you choose LT6373? I'm familiar with other InAmps with higher gain than LT6373 and also differential output.

    Regards,

    Kristine

  • Hi Kristine,

    I have investigated the ADA4254 (and ADA4255 & PGA280) but the 17nV/rtHz is just a little too high. It's so close but, according to our calcs, we lose a couple of bits of resolution to noise at the highest gains compared to two LT6373s.

    First prize would be something like the ADA4254 with <10nV/rtHz with its SPI interface. Let me know if something like this is coming.

    Thanks, Steve

  • Hi Steve,

    Yes, I was going to suggest ADA4254 and ADA4255, they are very suitable for your gain requirements. We do have AD8222 with high gain capability and about 8nV/rtHz noise and AD8295 with high gain capability and 8nV/rtHz input noise. Unfortunately, these 2 are not PGAs and uses resistor variable gain settings. I would think placing LTC6373 in series would be the best option for us now. Aside from the tradeoffs I mentioned previously, this config looks good to go. You can try this out first using our LTSpice simulator.

    Regards,

    Kristine

Reply
  • Hi Steve,

    Yes, I was going to suggest ADA4254 and ADA4255, they are very suitable for your gain requirements. We do have AD8222 with high gain capability and about 8nV/rtHz noise and AD8295 with high gain capability and 8nV/rtHz input noise. Unfortunately, these 2 are not PGAs and uses resistor variable gain settings. I would think placing LTC6373 in series would be the best option for us now. Aside from the tradeoffs I mentioned previously, this config looks good to go. You can try this out first using our LTSpice simulator.

    Regards,

    Kristine

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