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BQ34Z100: current sense resistor

tech16
Prodigy 205 points
Part Number: BQ34Z100

Tool/software:

Hello,

We plan to use the BQ34Z100 chip in our drone project. Since the operating current is relatively large, we want to choose a current-sensing resistor within the range of 0.2 milliohms to 0.5 milliohms. Could you please tell us if this resistance value is appropriate, and what is the recommended range of resistance values for current-sensing resistors for this chip?

  • 0
    TI__Mastermind 25475 points

    Hello,

    This question has been assigned and will be reviewed when possible.

    Thank you,
    Alan

  • +1 in reply to Alan Frias
    TI__Intellectual 1010 points

    Hello,

    The current-sensing resistor is typically in the range of 5mΩ to 20mΩ. A sense resistor too low will likely cause linearity issues. To ensure accurate current measurement, the input voltage generated across the current sense resistor should not exceed +/–125 mV.

    Thanks,

    Adam

  • 0 in reply to Adam Eschler
    Prodigy 205 points

    Hello,

    Thank you very much for your answer！I have another question I'd like to ask.
    Our chip needs to be used in a drone project, with a continuous operating current of 100A. We want to use a current-sensing resistor with a resistance range of 0.3-0.5 milliohms. Are there any other recommended chip models or solutions?

    Thanks,

    Tech16

  • 0 in reply to tech16
    TI__Intellectual 1010 points

    Hello,

    BQ34Z100 is your best option. The smallest I have seen a sense resistor and still be accurate is 0.5 milliohms. The measurement accuracy should be the same using a 0.5 mohm sense resistor compared to a 5 mohm sense resistor. The problem that you will have with smaller sense resistors is with the ADC offset. The accuracy with detecting smaller current will be reduce. The typical input offset error is 10uV, so the device can detect down to 10uV/0.5 mohm = 20mA with a 0.5mohm sense resistor. This should be okay with your set up.

    Thanks,

    Adam