BQ25820: Issue indicated by STAT1 and STAT2

Gary Zeng

Part Number: BQ25820
Other Parts Discussed in Thread: BQSTUDIO

Tool/software:

Hi team,

My customer is using BQ25820 in Humanoid robot battery buckup bag and met an issue that STAT1 and STAT2 led is lighting.

They find that there is no TS issue.

Q1: How do they figure out if there is a safety timer fault. what is the safety timer fault.

Q2: Could you please help check the schematic and see any faults.

05_charger(1).pdf

Below is the words on the left and top of the schematic.

1. Overvoltage charge cutoff voltage is not set;
2. Undervoltage charge cutoff voltage is 47V;
3. Set charging voltage to 41.9V;
4. Bus current limit is 6A;
5. Charging current is 2.5A;
6. Charging input voltage is 44.8V~67.2V, battery 10S ternary lithium

1 month ago

0 Aaron Bagger 1 month ago

TI__Prodigy 720 points

Dear Gary,

Could you provide me a register dump so that I can check what the IC is reading.

Thanks,

Aaron

0 Gary Zeng 1 month ago in reply to Aaron Bagger

TI__Intellectual 1135 points

Hi Bagger,

Could you please help compare below EVM and Customer board's registers and find the root cause of the lighting of STAT1 and STAT2.

Registers from EVM and customer board.doc

0 Aaron Bagger 1 month ago in reply to Gary Zeng

TI__Prodigy 720 points

Hi Gary,

Thank you for this information, I'll be looking more into this.

0 Aaron Bagger 1 month ago in reply to Aaron Bagger

TI__Prodigy 720 points

Hi Gary,

After inputting the registers into BQStudio I see that the input undervoltage fault as well as the drive supply fault were triggered. Can I see a waveform of the input and DRV_SUP pins when these faults occur?

Best Regards,
Aaron

0 Gary Zeng 1 month ago in reply to Aaron Bagger

TI__Intellectual 1135 points

Hi Bagger,

previous issue is solved. DRV_SUP should be connected with GND by a CAP and with REGN by a resistor.

New issue is that SW point has an oscillation when load is light.

CH3 is the output. As you can see, there is a oscillation.

CH1 is the upper half-bridge's driver and CH2 is the SW point's waveform.

Why driver and SW both have oscillation when load is light and output is not stable in picture 1.

0 Aaron Bagger 1 month ago in reply to Gary Zeng

TI__Prodigy 720 points

Hi Gary,

I will be looking more into this and will get back to you with updates.

Best Regards,

Aaron

0 Aaron Bagger 1 month ago in reply to Aaron Bagger

TI__Prodigy 720 points

Hi Gary,

It seems the IC is just in DCM mode. The ripple you see is normal at light loads.

Best Regards,

Aaron

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BQ25820: Issue indicated by STAT1 and STAT2