AD9244: Analog I/P impedance

Document created by analog-archivist Employee on Feb 23, 2016
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AD9244 what is the impedance of the analog inputs besides  the 10pF mentioned
in the datasheet


The Vin+, Vin- inputs, look directly into the unbuffered sample and hold
amplifer (datasheet figure3), the inputs see a dynamic input  impedance. It is
necessary to drive the AD9244 from a low impedance source with sufficient drive
capability to charge the sampling capacitors within the sampling period. A
number of strategies for driving the ADC are given in the datasheet – for
undersampling applications where the input bandwidth exceeds Fs/2 a wide band
center tapped transformer provides the optimal SFDR as well as performing
single ended to differential conversion.