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BQ76942: BQ76942 : resistors to pass transistors

priyank Agarwal
Prodigy 85 points
Part Number: BQ76942

I wanted to understand how the resistor value and package was selected for the EVM reference design. As per the reference design, if the given resistor is used, it will burn due to a power dissipation breach.

The resistor package used is 150ohm, 1W, 2512.

The maximum rated current is 160mA during a short circuit of both LDOs. The power dissipation on each resistor during this is 3.84W. This is much greater than the rated value.

  • 0
    TI__Mastermind 42060 points

    Hello Priyank,

    Yes that'd be possible, if both regulators were to be shorted. The EVM was made for simple evaluation of the device.

    More typically the short-circuit protection current would be much less than 160-mA. You would want to choose the resistor based on your expected current, and you can size it based on how much voltage you'd like the resistor to handle and how much you are expecting it would dissipate. The resistors in this path helps lessen the voltage burden on the BJT, as some of the voltage drop will be seen by the resistors.

    You can use multiple resistors in series or in parallel to handle the wattage.

    Best Regards,

    Luis Hernandez Salomon