BQ76PL455A: Value of Balancing Resistor

GUNIT SINGH

Part Number: BQ76PL455A

Hello All,

I am designing a PCB for BMS using bq76pl455 ic. In BQ76PL455 EVM Ti has used a balancing resistor of 75 ohms which provide maximum balancing current of 56mA. So I wanted to ask whether 56 mA current will be sufficient to balance the cells or I should lower the value of resistor?

Also, if we use a lower resistor value what precautions should be taken while designing PCB?

Regards,

Gunit

over 7 years ago

0 Roger Hwang over 7 years ago

TI__Genius 10785 points

Yes, you can lower the balancing R to increase the balancing current.
Only thing you need to worry is FET selection( should not be too much issue) and thermal of your PCB. Basically, that's all you need to worry about. Typical 150mA to 200mA is the range.

0 GUNIT SINGH over 7 years ago in reply to Roger Hwang

Intellectual 690 points

Thanks for replying.

I have seen that in current schematic of BQ76Pl455 EVM the mosfet which are use by Ti support max. current of 330 mA.
So can I use a resistor of 20 ohms in my design in that case the max. balancing current will be around 200mA ?

How can I take care about thermal management of PCB ?

Regards,
Gunit

0 Roger Hwang over 7 years ago in reply to GUNIT SINGH

TI__Genius 10785 points

I think that should be fine.
You can find good materials in Google.

You can calculate the power by how many cells you are balancing.
thermal via and good layout are key.

Power management

Power management forum

BQ76PL455A: Value of Balancing Resistor