High current monitoring with bq76940

Mark Cutler

Other Parts Discussed in Thread: BQ76940

Hi,

I'm building a battery management system using the bq76940. The load will draw ~200 A continuous with over-discharge protection needed at around 400-500 A and short circuit discharge protection needed around 600-700 A.

I'm pretty new to power electronics. Does anyone have any suggestions for the current sensing resistor? Following the suggestions in the documentation, a .3-.5 mOhm resistor would work, but it would need to dissipate 20 W or more under typical loads. I would like to keep to relatively inexpensive surface-mount components if possible. My ideas so far have been to

1) Use 2 or more resistors in parallel for Rsns such that no resistor needs to dissipate more than 10 W or so.

2) Use a hall-effect sensor (such as one from the ACS770xCB series by Allegro) combined with a voltage divider to get the output voltage in the +/- 200mV range.

Would either of these work? Any thoughts/suggestions would be appreciated.

Thanks,

Mark

over 9 years ago

0 Roger Hwang over 9 years ago

TI__Genius 10785 points

Hi Mark,

Application engineer who supports this product is on holiday vaction until Jan 4.

Do you think you can wait until he returns?

0 Mark Cutler over 9 years ago in reply to Roger Hwang

Prodigy 30 points

Hi Roger,

Yes, no problem. I can wait. Thanks for letting me know.

0 WM5295 over 9 years ago in reply to Mark Cutler

TI__Guru 54715 points

Either method should work. The part is designed with a resistor in mind. The smaller the resistor the larger the range but the lower the resolution for current measurement, so select a value suitable for the system.

A sensor may work as well if interfaced to the input signal levels of the IC. Be aware of any response times of the sensor circuit and their effect on the system.

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High current monitoring with bq76940