Analog input impedance of LTC2295

Question

Hello. 
 Can you provide analog input impedance(AINA&plusmn;, AINB&plusmn;) data of LTC2955. 
 Can we consider 1 M&Omega; or more based on the following conditions? 
 
 Best regards.

JAlipio · Accepted Answer

Hi baggio 
 Thanks for your interest in LTC2295. 
 Please see Input Drive Impedance on page 13 of the datasheet:

The input impedance is not constant and varies with the sampling rate and input frequency. Unfortunately, there is no available S-parameter Model for this ADC. 
 The analog input will be high impedance, that is why we recommend terminating the ADC externally with 50 ohms and match to that instead of matching to the ADC itself.)

PMH2023 · Answer

Hello,

One may want to consider using the ADC driver below for converting single-ended to differential signal to achieve higher level of performance below 100 MHz. The reason is that a transformer-based solution still needs to be driving by a single-ended amplifier that will need to drive the 50 ohm differential load (across ADC) which will likely lead to lower HD2/HD3 performance compared the ADC driver solution operating from a 3.3 V or perhaps 3 V supply.

LTC6419 Datasheet and Product Info | Analog Devices

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Analog input impedance of LTC2295