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bringing bias current from off-chip

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sharkies

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I need to bring in a very low DC current (2uA) from off chip.
The DB is already sent so it's too late to make changes,, but I just wanna know if 1uA from off-chip is even possible.

Basically i have a diode connected transistor onchip and an offchip external resistor will be placed to supply the 2uA current. But 1uA current seems so little.... Is it possible to do this? Perhaps regulator will help?(I don't know anything about regulators, so I'm not sure)... Let me know ASAP thanks
 

Hello,

First of all ... what kind of pad is your on-chip diode connected to? Hopefully an analog pad since the digital pads have their own drivers.

Building a current source for the mA is range isnt a problem using a an opamp, resistors, etc (see p.9):
**broken link removed**

But getting precision in the uA range might be harder. I guess you just need high precision resistors for the layout I showed above.

I will see what I can find ...

analogLow

analogLow
 
I see you might only use this external current for test.
1uA seems very small. In my experience, IC with PCB leakage will have ~1Mohm parasite resistance.
Maybe 2uA is much better.
If you only use it for chip evaluation, you can try 5uA that is much safer.
 

At this point your attention would have to turn to the board
and package, how to minimize the inevitable noise pickup that
will try and ride on that microamp. Route the resistor tight to
the appropriate return and hope you don't have a whole lot
of supply / ground noise bouncing the die away from the
board level reference.
 

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