Differential Input Resistance

Document created by analog-archivist Employee on Feb 23, 2016
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Please could you confirm whether the AD9253 and AD9257 have a differential
input resistor on their analogue inputs? The DC characteristics section of the
datasheets specify 5.2Kohm “Differential Input Resistance”, but there is no
differential input resistor shown in the equivalent circuit for the analogue
inputs or in the “ANALOG INPUT CONSIDERATIONS” section.

 

There is no differential input resistor as a component placed at the AD9253 and
AD9257 inputs. There is an equivalent resistance due to the switched capacitor
input circuit. It is not a simple shunt or series resistance, but we need to
pick a lumped model to use (shunt or series) and report the closest
approximation.

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