BQ25895: NTC values wrong

Co Ve

Part Number: BQ25895
Other Parts Discussed in Thread: BQ27441-G1,

Hi,

We have a PCB with a BQ25895 charger (BQ25895RTWR) and a BQ27441 fuel gauge (BQ27441-G1).

However, when my battery is in UVLO (Undervoltage Lockout) mode, the battery NTC voltage, which is connected to the TS pin along with a resistor divider bridge, is always showing 1.7V, which is consider "HOT", even though the actual NTC resistor value is 10kOhms, which is 25 degrees Celsius.

My question is: Is there a way to add an sofware offset to the NTC detection value, to make the "Hot" detection voltage to a higher value, rather than the current 47.75% - 48.75% that it is currently?

If not, can we temporarly ignore the NTC "Hot" reading a enter pre-charge mode, with a low current? That would pull the battery out of UVLO and solve my problem.

Thank you

Kind regards

over 3 years ago

0 Ning T over 3 years ago

TI__Guru 57331 points

Hi,

The VTS% thresholds are fixed. The host may overwrite the charging parameters (e.g. charging current) as needed.

Thanks,

Ning.

0 Co Ve over 3 years ago in reply to Ning T

Prodigy 170 points

Thanks, but the charger is not charging the battery at all, because of the "Warm" condition. Is there a way to bypass that and charge the battery anyway?
Kind regards

0 Ning T over 3 years ago in reply to Co Ve

TI__Guru 57331 points

Hi,

In this case, you may re-design the RT1 and RT2 to change the hot/cold temperature window. More details are in section 8.2.7.5 Thermistor Qualification on the d/s and the BQ2589x Calculation Tools (Rev. A) at http://www.ti.com/product/BQ25895/toolssoftware

If TS function is not needed at all, it can be bypassed. Please refer https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/874557/faq-bq25890-faq-bq2589x-schematic-review-and-pcb-layout-design-tips for BQ2589X: Schematic Review and PCB Layout Design Tips.

Thanks,

Ning.

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BQ25895: NTC values wrong