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I have the device configured for internal reference with a 0-5V input range. (SEL to ground; IN_N to Vref). I am using AC coupling with IN_P to 0.45V using a 2K to ground and 20K to +5V. When I power up the device IN_P goes to 0.45V as expected. When the clock starts IN_P rises to 0.6V. To me, that implies a sampling current of (0.6 - 0.45)/2K = 75uA. That is larger than I expected. Is this normal?
Greetings Jim and thank you for looking at this.
In my application I am looking at pulses. The signal line is usually low, but has pulses that can go as high as +5V. I don't have a problem with 75uA coming out of the input pin, as long as I'm not damaging the device and the current is predictable (say 50uA to 100uA). If I am damaging the device or the input current can vary significantly in this configuration then I must change something. (More clarification: I suspect the input current will depend on the input voltage. If IN_P is 2.5V I suspect input current will be much smaller than 75uA. My concern of predictability is for my "between pulse" or normal situation when the voltage at IN_P is 0.45, or rather 0.6V.)
Thanks,
Len