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INA240: High-Side Current monitoring application

Nicolas CORMIER
Prodigy 30 points
Part Number: INA240
Other Parts Discussed in Thread: LMP8640, INA200, INA193, INA282, INA301, INA195

Hello,

I want to use the INA240A2 in High-Side Current monitoring with electrical treatment to obtain the three motor phases equivalent current with one shunt/amplifier. (for cost and size reduction)

The sboa163a Fig3 application note describes this configuration.

In our design the power supply can vary from 15.5V to 46Vdc transient even 70V in lightning surge.

In our configuration, the measured current will be in discontinuous mode with high di/dt ( roughly 200A/µs, 20kHz switching frequency). Is the INA240 is adapted to this use or what other reference will be more compatible?

Thanks for your reply,

Regards

  • 0
    TI__Mastermind 27390 points

    Hi Nicolas,

     

    Thanks for choosing TI.

    If I understand your requirement accurately, during normal operation the current sense amplifier will see a constant common mode voltage, and a differential input step of 20KHz; The actual profile of the differential step will be determined by the current profile and shunt impedance.

    With these conditions in mind, INA240 should fit, however we have a number other potential candidates, including but not limited to INA193, INA200, INA282 and LMP8640 families. Aside from electrical specs, they differ in terms physical size and unit cost. I recommend review them based on parameters that are important to you.

    Hope this helps, let us know if you have any more questions or if this resolved your issue.

    Regard, Guang

  • 0 in reply to Guang Zhou
    Prodigy 30 points

    Hi Guang

    Thanks a lot for your fast reply.

    The INA240 is given  for 2V/µs slew rate but around  10µs settling time. It's too long compare to 50µs PWM period.

    The INA193 is given  for 1V/µs slew rate but around  2µs settling time. (faster than the previous one in some cases)

    The INA301 whitch  is seem to be suitable for my application is given  for 4V/µs slew rate but no settling time given. This parameter can it be given?

    My wish is to deform as little as possible the signal to be measured (0 to 4V output)

    Thanks for your precious help,

    Regards

    Nicolas

  • 0 in reply to Nicolas CORMIER
    TI__Mastermind 27390 points

    Hi Nicolas,

     

    Judging from Figure 24 of the data sheet, INA301 settling time is probably around 2uS as well. I agree INA301 will give faster large signal response compared with the other two.

    Regard, Guang

  • 0 in reply to Guang Zhou
    Prodigy 30 points
    Hi Guang

    I think that this high side measurement risks to be difficult.
    The phase current of 6 steps motor control is almost a square waveform.
    If I want to measure only the positive current of each phase, sum it to have almost continuous current with ripple, the measurement seem to be more easy.
    The INA195 is interesting for space saving ( 3 functions for 1 initial) and can accept reverse current if I believe the Fig29 of datasheet.
    The output of INA195 would use as "rectified" measurement. CM voltage from 13V to 32V steady state.
    Can this component be used in this case without troubles or others amplifiers problems as phase reversal etc...

    Thank you very much,

    Regards, Nicolas
  • 0 in reply to Nicolas CORMIER
    TI__Mastermind 27390 points

    Hi Nicolas,

     

    I hope all is well and sorry for the late reply.

    The bidirectional topology should work. The device functional mode descriptions still apply, as in section 8.4.2 in the datasheet. If low current level is a don’t-care, then it can be disregarded.

    Common mode voltage in range (-16V, 80V) will not cause phase reversal. I think this is what your concern is.

    A bit more on this topic however - some older amplifiers, when subjected to large differential input voltages, will exhibit this behavior. This device is one of them. The triggering level (many volts), nevertheless, is far away from the upper limit of the linear input range. Therefore during normal operations, the chance of phase reversal should be virtually 0. I think the only chance a phase reversal will ever happen is when the sense resistor vaporizes. And the full DC bus voltage appears across the input.

    Since your input current is step waveform, it will be better to have low inductance sense resistors. If ringing is a potential problem, you may consider putting ferrite beads in the input sense lines. The optional input filters can aid in tamping down such ring as well.

    Regard, Guang