1
\$\begingroup\$

I am working on a project in which I am required to sense current in micro ampere range from a 2kV power supply. Here is a link of an article which I am referring.

https://www.maximintegrated.com/en/app-notes/index.mvp/id/1867

High Voltage micro current sensing

While Searching on google I found that in high side current sensing the common mode voltage range should include the supply voltage (that i am providing to the load) within its range. The common mode voltage range of the max4172 IC used in the circuit is +2V to +32V. Will it support my 2kV supply. if not, could anyone please suggest an alternative solution to this problem.

*Also i am confused about the 9v battery and 1000v. Why their positive side is connected to the same node?

Thanks in advance!

\$\endgroup\$
2
  • \$\begingroup\$ What is you goal - overcurrent protection or precise measurement? Defining the exact current range would help too. \$\endgroup\$
    – Todor Simeonov
    May 27, 2017 at 10:11
  • \$\begingroup\$ My goal is precise measurement of current within a range of 0 to 830 micro amps \$\endgroup\$
    – Sabheeh Ali
    May 28, 2017 at 6:53

1 Answer 1

Reset to default
2
\$\begingroup\$

The common mode range of the MAX4172 is measured with respect to its supply. As you see, it is powered by a floating 9v battery, which provides rails of Vin and Vin-9v.

If you duplicate the circuit you have presented, then it will have a rail of 2kV, and a ground of 1993V. This puts the 2kV input's common mode of 9v squarely in the 2V to 32V range required.

If you don't want to use a 9v battery, then you will need to provide a similar high-side supply arrangement possibly from your input voltage, or some other isolated converter. There are other ways, depending on the duty cycle of your supply.

\$\endgroup\$
2
  • \$\begingroup\$ i am confused about the 9v battery and 1000v. Why their positive side is connected to the same node? \$\endgroup\$
    – Sabheeh Ali
    May 28, 2017 at 6:59
  • 2
    \$\begingroup\$ Consider the 4172 rails. If batt-ve went to 1000+ve, then you have 1000 and 1009, and the sense resistor is outside the CMR. If batt-ve went to GND, then you have 0 and 9, and the sense reisstoor is outside the CMR. If batt+ve went to GND, then you have -9 and 0v, and the sense resistor is outside the CMR. Only by connectign batt+ve to 1000+ does the sense reistor end up with the CMR of the 4172. \$\endgroup\$
    – Neil_UK
    May 28, 2017 at 7:18

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.