UCD3138: Questions of UCD3138 pin impednace

Hello,

An engineer is looking into this and will respond.

Hi Experts,

Any update?

Hi Experts,

Any update?

I can't think of any reason why AD02 should have a significantly different impedance than any other ADC pin.  What kind of impedances were you measuring?  

What is your setup?  I assume you have the UCD powered up, and the voltage you are applying to measure impedance doesn't go outside the power rails?  

If the UCD isn't powered up, or your input voltage goes outside the power rails, then the protection diodes may come into play.

Of course if it's on one of our EVMs, even the open loop board, there may be components on the board hooked up to the pins as well.  

Also, for you information, July 4 is a national holiday in the US.  

There's no reason that AD02 should have a significantly different impedance.  How much difference did you see?  What setup did you have?

Were you using a TI EVM or some other board?  Did you have the UCD powered up?  What voltage were you applying to measure impedance?