AD9600 input impedance

Question

Hi all, 
 What is the AD9600 input impedance ? Cin : 8(typ) pF Rin : ?(typ) ohm 
 When we will start to design the differential analog input configurations, "Figure 47. Differential Transformer-Coupled Configuration", Is it correct that we just design with reference to "Table 10. Example RC Network" without considering the input impedance? 
 In the AD9600 EV-board pcb pattern, what is the characteristic impedance of transmission line, 
 from the Differential Transformer to ADC Vin ? 
 Best regards, sss

FormerMember · Accepted Answer

Hello, 
 The AD9600 is the 10-bit version of the AD9627. Link to S-parameter for the AD9627 (and AD9600) is below. You can use this S-parameter model along with transformer +R-L-C components when designing an input network for the AD9600 (see app note AN827 link below). Note that termination resistor that sets input impedance to ADC should be located close to ADC input. 
 One can use Table 10 as a guide line to what values should be used for simple R-C network depending on input frequency. The transformer/baluns on the EVB are 1:1 hence one would expect traces to DUT should be closer to 25 ohms given that differential traces are loosely coupled (due to separation). 
 Regards. 
 . 
 http://www.analog.com/en/search.html?q=AD9627 
 http://www.analog.com/media/en/technical-documentation/application-notes/577685821057469457705578853404381574892535191189340957AN_827_0.pdf)

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AD9600 input impedance