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Original question:

bq78250 Question

BQ76920: BQ76920 overcurrent protection

Adam
Expert 1195 points
Part Number: BQ76920
Other Parts Discussed in Thread: BQ78350, , BQ76200, BQ2970

Hello,

I've got a question regarding hardware overcurrent protection in BQ796022 (working with BQ78350). There is a programmable threshold limit on current sense input (form 22mV to 200mV), so depending on shunt resistor value it turns off battery when the current exceeds the limit.

Is there any possibility to bypass this protection (apart of lovering the value of shunt resistor) so that device limits the current instead of causing battery to disconnect?

Because working with BLDC motor high currents spikes can occur.

Thank you for any support,

Adam

  • 0
    TI__Guru 54715 points

    Hi Adam,

    The BQ76920 does not have a way to mask off the individual protections, they are always active.  The BQ78350 expects them and the FET control to be present.  Threshold or sense resistor selection or filtering would seem to be the options available for the current input, or filtering the input to the BLDC controller for lower peak currents from the battery.

    When using your own MCU you might use some external logic and gate driver to determine when in system operation a short circuit or other fault should be prevented similar to the concept described in http://www.ti.com/lit/an/slua805/slua805.pdf .

  • 0 in reply to WM5295
    Expert 1195 points

    Thank you very much.

    I assume the solution with MCU works with bq76200 in order to drive the high-side FETs and the BQ2970 is not necessary, am I right?

  • 0 in reply to Adam
    TI__Guru 54715 points

    Hi Adam,

    Correct.  The BQ2970 was used in the ap note as a current detector separate from the BQ769x0.  It is not necessary but an option if the system design wanted such a function.  The MCU can control the BQ76200 directly if desired or with logic.