BQ25703A: bq25703A / Behavior at transition from supplement to battery operation

Let us try to understand it:

1. In the beginning, battery is in supplement mode.

2. When Vin is below Vin-dpm, converter cannot deliver input power to output. So, the battery support full load current.

3. When Vin goes down around UVLO threshold, CHG_OK flips. The internal logic loss power. That may cause that battery pulse current.

To understand it better, you can zoom in that area and monitoring SW2, CHG_OK, LODRV2 waveform. I am going to do the same test in the lab. And then, we can understand it better.

Also, if we disable the low power mode (set charge option 0 bit [15] to 1), the internal logic should keep the power. And, we may avoid this battery current spike.

On my bench, the HIDRV1 and SW2 voltage jumps up on that region (CHG_OK from high to low) on both low power mode and non-low power mode. But, IBAT doesn't have the glitch.
Would you use CHG_OK as the triggering source to zoom in that area and monitor the IBAT glitch? I want to know is the IBAT glitch real or just measurement noise?

Hi Wang,

Thank you for your support.

Today I tried the same measurement with actual battery and confirmed the same glitch on battery current. As additional information, I found that this glitch is occurred at the same timing with CHG_OK from high to low. Please refer attached photo for hardware setting. And I just disable watchdog timer and change input current limit setting to 500mA as attached screen shot.

Please let me know if you need more information.

Best Regards,

Satoshi / Japan Disty

On my bench test, there is no IBAT difference between 500mA input current limit setting and other input current limit setting. What test condition difference is between your first test waveform and last test waveform?

Hi Wang,

All waveform are taken with the same condition. The last waveform show Isys, not Ibat. It means that the glitch can be seen on Ibat however there is no glitch on Isys.

Best Regards,
Satoshi