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anti-alias-filter for fully differential ADC driver

Question asked by Alexxx on May 24, 2018
Latest reply on Jun 4, 2018 by Alexxx

There is a difficulty when having differential source signal to drive differential ADC.
The ADC driver must have very high bandwidth. So any anti-alias-filter has to be in front of it.
But the filter has to be differential also!
There is a filter circuit for the LTC6363 (data sheet page 35). But as it has several resistors in each gain path with special values.
So it is NOT possible to get all the resistors in one network. With single resistors the ratio and TC tracking is relatively bad,
which in turn will severly degrade CMRR and the gain stabiltity.

As this is a standard task for many applications, I wonder why there is (almost) NO differential ADC driver that has the capability to add a (AAF-) filter-C to it without compromising specs.
(The only INA - AD8428 has fixed gain of 2000 - way too high!).

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