BQ25896: vindpm issue

Hi Yikuang,

Can you provide a register dump while charging is enabled and a second register dump when charging is disabled?

Also can you provide a scope capture that shows VBUS, IBUS, VBAT and IBAT? VBUS, IBUS, VSYS, ISYS?

VINDPM function will not disable charging. It will reduce charging current to 0A if VBUS continues to droop but charging will still be enabled and STAT pin should be low. If VBUS rises back to regulation voltage charging will continue without the need for a re-enable command.

 After you see the charging is disabled, do a full register read and look for any fault conditions in REG0C as a start. Charging can be disabled if VBUS falls below VBAT + VSLEEP, if the battery hits the overvoltage threshold, or if VSYS hits the overvoltage threshold to list a few examples.

Regards,

James

James,

Continuing to this question!! I also post in E2E few minutes ago.

VINDPM function will not disable charging. It will reduce charging current to 0A if VBUS continues to droop but charging will still be enabled and STAT pin should be low. If VBUS rises back to regulation voltage charging will continue without the need for a re-enable command.

==> Can you advise the VBUS's hysteresis voltage level when charging re-enable during VBUS voltage rises back?

Thanks

Hi Paul,

There is no specific hysteresis associated with the VINDPM threshold since the BQ25896 will adjust the charging current fluidly in an attempt to keep VBUS at the VINDPM threshold (accuracy of +/- 3%). This can be seen if you slowly reduce the voltage at VBUS below the VINDPM threshold, you will see the charging current ramp down once VBUS reaches the VINDPM threshold. Once the charging current can no longer be reduced to stabilize VBUS, the voltage drops further below VINDPM threshold. Below I have provided a scope capture of VBUS and IBAT to illustrate the sensitivity. VBUS voltage is stepped down at the input supply but the charger reduces the current IBAT to keep VBUS at ~4.40V. 

ICHC = 1.472A; VINDPM = 4.40V; Sweeping VBUS between 4.5V and 4.3V

For an additional visual of the VINDPM behavior, see Section 9.2.6.2 in the datasheet. If the VBUS input is being overloaded by the battery charge current, VINDPM will reduce the charging current until VBUS stabilizes.

If the current draw from VSYS is causing the overload, the battery charging current will first be reduced since the SYS load is prioritized. If the charging current reaches zero and the VBUS overload condition is still present, VSYS will begin to drop. Once VSYS drops below VBAT, the charger will enter Supplement mode and the battery will assist with supplying the SYS current. 

If the overload condition is removed, charging current will ramp up alongside the VBUS voltage.

Regards,

James

Hi James

below is the vaule when charger in stop charging stage(refer to the picture thatI posted)

May I know if the charger in supplement mode with reading register?

Hi Yikuang,

Can you provide a full register dump that shows all the values before and after charging stops? If you have a schematic for the system please share it here as well.

Based on the register values you showed above, your device is reporting "Not Charging" (REG0B[4:3]) but the ADC is reading a charge current of 600mA (REG12[6:0]). I also noticed that your device is not detecting an input at VBUS (REG0B[7:5]) but the ADC is reporting that VBUS = 4.8V and VBUS Good says that "VBUS is attached" (REG11[7]) .

I need to see the full register dump before and after charging stops for a better analysis. I recommend you confirm that the battery is not drawing current when charging is reported as disabled.

When the charger is in Supplement Mode, VSYS should be below VBAT. You can check the ADC output at REG0E[6:0] (VBAT) and REG0F[6:0] (VSYS) to check if the system voltage is below the battery voltage. Additionally, if the charger is in Supplement Mode the ADC should report a charge current of 0A at REG12[6:0] since current is flowing out of the battery and to the system. VBAT needs to be above the depletion threshold for Supplement Mode to remain active.

Also, REG13[7] will report "VINDPM" to indicate that the adapter is overloaded during Supplement Mode, and you can check REG11[6:0] to see if the VBUS voltage has dropped to your VINDPM threshold limit (Set by REG0D[6:0]).

Regards,

James