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INA199-Q1: Two shunt resistors for INA199B1DCKRs

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Prodigy 30 points
Part Number: INA199-Q1
Other Parts Discussed in Thread: INA199

Tool/software:

Hello,

I'm designing a current measurement circuit using the INA199B1DCKR for monitoring a DC brushed motor's drive current. Whether driven by DC or PWM, there's a significant difference between the average and peak currents.

Therefore, I'm considering using two shunt resistors: one optimized for accurate average current measurement, and the other for accurate peak current measurement. My idea is to place both shunt resistors in series on the low-side of the motor's drive current path. Each shunt resistor would then be connected to a separate INA199B1DCKR to convert the current into a voltage, which would then be monitored by two AD converters on a single CPU.

Could you please advise if there are any potential issues with using two shunt resistors in series on the low-side with two separate INA199B1DCKR devices? Also, if there's a better approach, I'd appreciate your suggestions.

Thank you.

  • +1
    TI__Mastermind 22275 points

    Hello!

    In terms of your first ask, there should be no issues placing two shunts in series here. 

    That said, can I ask what the measurable structure looks like here? You say you are potentially driving via PWM, would this be sinusoidal PWM, or something different? I am potentially concerned about BW on the INA199 for the peak mode current measurement, and I want to understand what the waveshape looks like here. Would it be correct to assume that ultimately the current you are sending to the motor would be sinusoidal in nature? Do you know roughly what frequency of sinusoid you would be measuring here?

  • 0 in reply to Carolus Andrews
    Prodigy 30 points

    Thanks for the prompt advice! This message helped us so much.