bq27421-G1 BIN connection when charger use thermistor

K. Sasaki14

Other Parts Discussed in Thread: BQ27421-G1, BQ24090

Can't we connect bq27421-G1 BIN pin with Battery pack thermistor when charger device use battery pack thermistor to monitor temperature?

I think BIN pin doesn't become Low in this case. The charger device is bq24090.

If my idea is correct, do you have any solution for BIN connection?

Best Regards,
Kohei Sasaki

over 9 years ago

0 Dominik Hartl11 over 9 years ago

TI__Guru 61646 points

The bias ciruits from the charger and the gauge for the thermistor will interfere so you should use separate thermistors for charger and gauge.

0 K. Sasaki14 over 9 years ago in reply to Dominik Hartl11

Guru 10200 points

Dominik-san,

Is there any problem when there is no 10k pull down on BIN pin with "BIE" bit is 0 setting?
We understand it is recommended that BIN should be pull down even if "BIE" bit is 0.
However our customer has already finished their circuit design.

Should it be fixed?

Best Regards,
Kohei Sasaki

0 Dominik Hartl11 over 9 years ago in reply to K. Sasaki14

TI__Guru 61646 points

Without this pull-down, this pin will float. Please ask your customer to add the pull-down resistor.

0 K. Sasaki14 over 9 years ago in reply to Dominik Hartl11

Guru 10200 points

Dominik-san,

Thank you for your reply.
Our customer says adding the pull down resistor is difficult.
What does happen if there is no pull down resistor on BIN pin with "BIE" bit is 0 setting.

Best Regards,
Kohei Sasaki

0 Dominik Hartl11 over 9 years ago in reply to K. Sasaki14

TI__Guru 61646 points

The pin will float under certain conditions and you may see increased power consumption. I don't have concrete data.

0 K. Sasaki14 over 9 years ago in reply to Dominik Hartl11

Guru 10200 points

Dominik-san,

Is it only power consumption increasing?
Now BIN pin is connected to thermistor of battery pack, however the thermistor is used by bq24090. So halfway voltage is added to BIN.
Doesn't it effect to fuel gauge function?

Best Regards,
Kohei Sasaki

0 Dominik Hartl11 over 9 years ago in reply to K. Sasaki14

TI__Guru 61646 points

It won't have an effect on fuel gauge function if you keep it connected to the thermistor which is used by the bq24090. So it looks like your customer's design is ok.

Power management

Power management forum

bq27421-G1 BIN connection when charger use thermistor