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High frequency inductor current sense

user5273543
Prodigy 30 points
Other Parts Discussed in Thread: INA240, INA293, INA290, INA168

My control theme needs the point that the negative part of inductor current is larger than 0. I have tried to use current sense resistors, but it has so large switching noise that cannot get the exact point. I have tried to use Hall current sensor with no significant switching noise, but its bandwidth is too low to sense the current with frequency of 500kHz.

Does TI have the current sensor with no switching noise and high bandwidth?Or is there any current sensing method with frequency of 500kHz?The current shape is like the figure shown below:

  • 0
    TI__Mastermind 32290 points

    Hello,

    I think you may have had issues loading your figure as I do not see it.  I assume you need to have a device that can handle the common mode voltage switching at higher frequencies.  Depending on you current you are looking at and the voltages I have some suggestions but they are limited.  We have the INA240 which rejects PWM signals or high common mode voltage changes.  The benefit is this device is bi-directional but has a limited bandwidth or 400kHz.  If you do not require the bandwidth but the rejection then this device may work.

    For higher bandwidth we have the INA293 or the INA290 (in preview mode)  These two have higher bandwidth but have some limitations and are not bi-directional.  both these devices will require to recover from negative Vsense voltages so if the voltage they are sensing are negative then come back to normal operating voltages this will reduce your bandwidth as the recovery time is not the same as the bandwidth.

    If I am correct in what you are looking for you can see some our older devices like the INA168 have large bandwidth but the AC CMRR  is what you will need to worry about and the bandwidth of the INA168 will be dependent on the Gain resistor you select.

    These are the analog solutions I would recommend.  

  • 0 in reply to Javier Contreras4
    Prodigy 30 points

    Hello,

    This document is the shape of inductor current, I hope to obtain the Q4 switching time which is the point of current that is equal to -Izvs(exact number known in advance). The switching frequency is 500kHz, So what i am looking for is the device with high bandwidth and large AC CMRR .

    I have tried to use Hall current sensor(ACS430) which is good with no swtiching noise,but the maximum bandwidth is 2MHz.Do you know some other Hall sensor with higher bandwidth?

    Best Regards,

    Jade

  • 0 in reply to user5273543
    TI__Mastermind 32290 points

    Hello Jade,

    Our analog solution will not work because the device will not be fast enough.  Our current hall sensors do not have the bandwidth you require either.

    Our high speed amplifiers may be an option but they may be limited on the common mode range and that is why I assume you are attempting to use a hall sensor.