PGA281: monitor uA level current

Hi Ben,

Ben Kuo said:

I am looking for high side current monitor solution to measure ~10uA level current at 48~60VBUS.

With the high common mode 40-60Vbus voltage, PGA281 is unable to accommodate the measurement. If you have to use PGA281, then you have the sense the current on the low side, but ~10uA will be touch to make accurate measurement, if GND noise is high. 

There are a few suggestions. 

1. Use OPA596 or similar High voltage difference amplifier to make the delta voltage across the shunt.

2.  Use INA592 to make the high side current measurement, then use PGA281 or other instrumentation amplifier to convert the current to voltage (may have leakage current dilemma)

3. If a precision op amp can be bootstrapped near the high side voltage range, this is also a good method to make a current measurement. 

4.  Use INA240 current monitor to sense the current on the high side (current monitor support team)

5. Use precision voltage divider (e.g. RES11A  or similar) to lower the common mode voltage and use PGA281 or other IA. The voltage divider may have leakage current errors that the application may not be suitable per the measurement. 

The options 1-4 are the best bets to make the accurate current measurement. What is your application? Are you trying to measure the leakage current in battery during the non-operating state?

Please let me know if you have other questions. 

Best,

Raymond