BQ76942: PACK & LD resistors

Derek Wilson

Part Number: BQ76942

Hello,

I was hoping to get some clarity on choosing resistors for the PACK and LD pins. As I understand it, these pins are for voltage sensing and don't have significant input currents. The evaluation board uses two 5.1k resistors in series on each, and these are 1206 packages with 1/4W ratings. Are these power ratings necessary, or is a single 10k 0603 sufficient for each pin?

Thanks,

Derek

over 1 year ago

+1 Luis H. S. over 1 year ago

TI__Mastermind 42060 points

Hello Derek,

A single 10-kOhm would work.

The LD pin also serves as a load detect pin, when load detect is active, there is a small current source connected from BAT and out of the LD pin, the voltage drop across the LD resistor helps the device determine if a load is attached or not. If load detect is not used, it may not be as important.

Additionally, these also would limit the current of a reverse-charger connection (If the reverse charger circuitry is in your system). Depending on the wattage seen by these resistors, different ratings may be required. Section 3 Reverse Charge Component Selection of the Multiple FETs with the BQ76952, BQ76942 Battery Monitors application note goes into more detail of the paths that a reverse charger can take.

Best Regards,

Luis Hernandez Salomon

0 Derek Wilson over 1 year ago in reply to Luis H. S.

Prodigy 40 points

Hi Luis,

Thanks so much! That answered my question.

Best,

Derek

0 Luis H. S. over 1 year ago in reply to Derek Wilson

TI__Mastermind 42060 points

Hello Derek,

Glad to help! .

Best Regards,

Luis Hernandez Salomon

Power management

Power management forum

BQ76942: PACK & LD resistors