AD9460: Application using DC input

Document created by analog-archivist Employee on Feb 23, 2016
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I want use AD9460 to read the output from a digital phase detector . The
output of the phase detector is differential. Dc compnent of the output is as
importnant as the AC component, so I cannot ac couple it to AD9460. On page 21
of AD9460's datasheet, it says the input should be ac coupled, otherwise
linearity and range would suffer. Could you please let me know more about it
like to what extent linearity and range could suffer and any technique to get
round this problem?

 

The Ad9460 is DC biased at 3.5V at the input, and so its Common Mode Voltage is
3.5V. An external Common mode Voltage must be between 3.2 V and 3.9 Volts for
optimum Linearity and noise performance.

All this means that, if you don't want to Ac couple your signal,  your input
circuit to the AD9460 must be centered around 3.5 V , for optimum performance.
You must also condition your input circuit, to ensure that the Dc component of
the Phase detection of your input does not vary between 3.2V and 3.9v, for full
range of your phase detection circuit.

Failing to do this may lead to undesired offset's etc.

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