BQ24650: Over temperature shutdown issue.

abhiraj pr

Part Number: BQ24650

Tool/software:

Hi TI Team

I have completely redone the PCB with maximum traces for heat dissipation but still the IC stops charging after 2-3 minute of charging. the charging current set as 2.0 Amps. The LED connected on Charging status (STAT1) goes off after 2-3 minutes of charging, and even when the charging current is 300mA the IC go to shutdown and starts after a while. attached revised schematics.

The PCB is a two layer one and BQ24650 and the switching mosfet on the same side and given 5 vias on the GND pad. when i compare with the EVAL board, the IC not at all heating on the eval board, but in my PCB the IC temperature goes 50 degree celcius while charging at 300mA current charging LED goes off immediatly. According to me there is no high current circuit through the IC and IC shouldnt get hot like this. the mosfet and the inductor are not getting hot compared to the charger IC.

SCH_BQ24650_V2.pdf

3 months ago

0 Christian Moyer 3 months ago

TI__Mastermind 32791 points

Hello Abhiraj,

I don't see any obvious issues with the schematic, can you confirm you followed the PCB layout guidelines:https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/1027295/faq-bq24610-bq24616-bq24617-bq24618-bq24630-layout-guidelines-and-example

Best Regards,

Christian.

0 abhiraj pr 3 months ago in reply to Christian Moyer

Prodigy 100 points

Hello Christian Moyer

I have followed the layout guidelines to the best possible. (this is my second revised PCB, first one had same issue even with 4 layers and based on the suggestion from the E2E community, re designed the PCB. but this 2 layer board is better than my previous 4 layer one in terms of heat dissipation) only difference is that the PCB is a two layer one and accordingly the routing is done. im sharing the layout here for your review and suggestions.

0 Christian Moyer 3 months ago in reply to abhiraj pr

TI__Mastermind 32791 points

Hello Abhiraj.

abhiraj pr said:
the IC not at all heating on the eval board, but in my PCB the IC temperature goes 50 degree celcius while charging at 300mA current charging LED goes off immediatly.

Thermal shutdown should be at 145C not 50C.

Can you confirm none of these other possible conditions could be the cause of this shutdown:

Best Regards,

Christian.

0 abhiraj pr 2 months ago in reply to Christian Moyer

Prodigy 100 points

Hello Christian

The issue was with respect to the temperature sensor (10KNTC) that is mounted on the PCB and the resistor combination was wrong.. (I used SMD Thermistor) after correcting the values of the biasing resistors now the IC working correctly.. However the IC become hot when the battery current goes about 500mA and above and no voltage drop on VCC pin of the IC. infact there is no high current path through the IC other than mosfet drive. at the same time the evaluation board is cool and it gets warm when the current increases above 1A.

0 Christian Moyer 2 months ago in reply to abhiraj pr

TI__Mastermind 32791 points

Hello abhiraj,

Can you confirm you followed this step "It is critical to solder the exposed thermal pad on the back side of the IC package to the PCB ground. Ensure that there are sufficient thermal vias directly under the IC, connecting to the ground plane on the other layers." Typically we recommned a four layer board over a 2layer board with 2 layers allocated for gound planes.

Best Regards,

Christian.

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BQ24650: Over temperature shutdown issue.