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INA190: measurement method at PWM input.

Part Number: INA190
Other Parts Discussed in Thread: INA180, INA212, INA185

Dear Sir,

My customer is using INA190A1 and input is PWM.

Input condition is below.

40Hz, Duty 60%, 1.5sec

40Hz, Duty 30%, 1.5sec

my question is below.
1. could you review the schematic.
2. when PWM input for INA190, how to measure precision method? now we use to measure output for using MCU ADC pin. do you have better precision method at PWM input.

TI Current-Sense Amplifier_191111.pdf

  • Hey Dexter,

    Thank you for your questions and data.

    40Hz is well within the bandwidth of INA190 and the ~18ms of time for the INA190 output to settle is plenty. So the INA190 should be fast enough and it seems to be tracking the input current according to your waveforms.

    I think one problem here is the instrumentation/ADC error especially with measuring the shunt voltage directly given how measurement is small and within the ADC recommended operating range. More averaging of the digital data could help reduce gain error calculations. How do you pick the points for calculating gain error?

    Depending on the ADCs sampling time, conversion time, and bit resolution it could be disrupting the output voltage signal of INA190. Consider placing an op-amp buffer at VOUT here to drive the ADC so that error from this is removed.

    Is this the fastest the PWM will move? Consider using the INA185, INA180, and INA212 as other alternative although the INA190 should work in this situation.