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Micro current measurement in 600V DC line

Rocky Chen
Expert 7855 points
Other Parts Discussed in Thread: INA190, OPA192, INA149, TINA-TI

Hi

My customer is looking for a analog front end circuit to support its post ADC to achieve a micro current (nA level) measurement in 600V DC line. Do we have suitable solution to propose?

Thanks!

-Rocky

  • 0
    TI__Mastermind 27715 points

    Hi Rocky,

    Thank you for your question! Our engineers will analyze and respond when we return to the office on Monday.

    Best regards,

    Ian Williams
    Applications Manager
    Current Sensing

  • 0 in reply to Ian Williams
    TI__Mastermind 24805 points

    Hello Rocky,

    Thanks for reaching out on the forum.  Can you clarify whether you are wanting to measure nA or uA, what exactly is your lower and upper current bounds? Does it matter whether you have a high-side or low-side sensing implementation?  If low-side sensing is acceptable, I think the INA190 would be worth considering.  Many of our devices have input bias currents that can be several micro-Amps, while the INA190 has a max input bias current specification of 3 nA.  While the INA190 can measure lower currents, its common mode is no where near 600V, so it must be used in low side sensing.  If high-side sensing is required for a nano Amp current reading, you will likely need to use a multi-chip solution involving the precision amplifier team.

  • 0 in reply to Patrick Simmons
    TI__Expert 7855 points

    Hi Ian, Patrick

    Thanks for reply.

    1) We want to measure nA

    2) Current range: 0~10nA, Accuracy is 1nA.

    3) High side is required, Maximum voltage is 600V

    Do we have suitable analog solution in front end?

  • 0 in reply to Rocky Chen
    TI__Mastermind 24805 points

    Hello Rocky,

    Those requirements are beyond the capability of our products specifically designed for current sensing.  However, the amplifiers product line might be able to give you a multi-chip solution for those design requirements.  I will forward your thread to them and see if they can help you.

  • 0 in reply to Rocky Chen
    TI__Guru 64680 points

    Rocky,

    Below please see one possible solution utilizing INA149 together with OPA192 bootstrapped near a positive rail.  You may use 500M shunt resistor, Rshunt, with a buffer OPA192, to directly convert 10nV into 5V, or a combination of a lower value Rshunt with proportionally higher gain of OPA192 (by varying R3) as shown below.  You must reference the output, VF1, to 1.5V or higher above the ground since this is the lower end of INA149 output voltage linear range.

    I have attached Tina-TI circuit schematic for your own simulation - see below.

    Rocky.TSC