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AD7606 - Capacitors on the REFIN/REFOUT and REFCAPA/B  pins

Question asked by JGordon on Nov 28, 2017
Latest reply on Dec 4, 2017 by NiallM

In the AD7606 Data Sheet there is some ambiguity in the required characteristics for the capacitors specified for the REFIN/REFOUT pin and the REFCAPA/B pins.  In one case it is specifically described as a 10 uFCeramic cap.  In the other case the capacitor is simply specified as 10uF.  In Figure 43 of the Data Sheet both capacitors are shown as polarized capacitors.  My application will be operating in an environment with significant vibration.  I am concerned about the piezoelectric effects of X7R ceramic caps introducing electrical noise into the reference circuit of the ADC.  What specifically are the requirements and limitations for these two capacitors?  Is low ESR the consideration driving the specification of a ceramic cap on REFCAPA/B?  I look forward to further insight.


J. Gordon

GMH Engineering