BQ24780S: Discharge current setting problem

Lumina Gui

Part Number: BQ24780S
Other Parts Discussed in Thread: BQSTUDIO

Hi TI Teams,

We have set the discharge current register (0x39H) of BQ24780S to 0x1400h (5.1A), but the actually measured discharge current is 6.12A. We have read the value of 0x39h register and got 0x1400, which means that the write was successful.

We need to do the notebook machine safety certification, the requirements of the continuous maximum discharge current needs to be within 1C (5.1A). The test environment for the BurnlnTest aging, the notebook plugged full USB load, that is, to simulate the maximum power consumption under the condition of the battery discharge.

Can you help to analyse the cause of this problem? The current sensing resistor (RSR) is 10-mΩ.

Thanks,

Kind Regards

over 1 year ago

0 Aya Khedr over 1 year ago

TI__Mastermind 31462 points

Hi Lumina,

Thank you for reaching out!

The default discharge current limit is 6.144 A (6.12A seems close to the default). Is the watchdog timer enabled?

What is the internal discharge current limit setting on ILIM pin?

Best Regards,

Aya Khedr

0 Lumina Gui over 1 year ago in reply to Aya Khedr

Genius 3710 points

Hi Aya,

The watchdog timer is enabled and the enable bit[14:13] is set to 11(175s).

For your question about the internal discharge current limit setting on ILIM pin. The bit[7] of register 0x38h is set to 0.

Thanks,

Kind Regards

0 Aya Khedr over 1 year ago in reply to Lumina Gui

TI__Mastermind 31462 points

Hi Lumina,

Could you try disabling the watchdog timer and see if you observe the expected discharge current?

Best Regards,

Aya Khedr

0 Lumina Gui over 1 year ago in reply to Aya Khedr

Genius 3710 points

Hi Aya,

Thanks for your suggestion. When we try disabling the watchdog timer, we found that the read value of ChargerOption0 register (0x12h) is always 0x2A54, no matter what value is written in it, even if 0x0000 is written in it, it is still 0x2A54.

Thanks,

Kind Regards

0 Aya Khedr over 1 year ago in reply to Lumina Gui

TI__Mastermind 31462 points

Hi Lumina,

Are you using bqStudio to evaluate? I would suggest disabling watchdog timer using the GUI first to see if that resolves the issue. Please let me know what you observe here.

Best Regards,

Aya Khedr

0 Aya Khedr over 1 year ago in reply to Aya Khedr

TI__Mastermind 31462 points

Hi Lumina,

I will close this thread since I have not received any updates.

Please feel free to open a new thread if you have further questions or concerns.

Best Regards,

Aya Khedr

Power management

Power management forum

BQ24780S: Discharge current setting problem