BQ25890H: CAN'T start charge after battery over discharge

any update?

Hi Jingguo, 

Please see my comments below. 

Jingguo Wang said:

And in this application, the system can't start up, so MCU can't write register for charge IC, so I want to know can the device work normal in default configuration? 

Yes the BQ25890H is expected to work normally in default configuration. It can perform a full charge cycle with default configuration. 

Jingguo Wang said:

and they found the charge can't charge after battery is over discharged. In this time, Vbus=9V,and charge current=50mA, but the battery voltage can't raise as expected.

What is battery over discharge voltage in the customer system? Do they relay on the BQ25890H over discharge protection or do they have a battery protector which cuts off battery from system beyond a higher threshold than the BQ25890H over discharge threshold (2.5V)? An external battery protector circuit could be a factor in preventing charge.

Additionally, BQ25890H is designed to be able to power-up system even if battery is deeply discharged. Is customer able to provide a waveform showing VBUS, VBAT, VSYS, and SW pin voltages at time when battery is not charging as expected? 

Best Regards,

Garrett 

Hi Garrett,

I found the issue is related to the voltage of VBUS, after the battery voltage is below 3V, like 2.3 or 2.7V, when plug in the adapter, sometimes, the voltage of VBUS is 9V, and sometimes, the voltage is of VBUS is 5V. the charge can work normal when the VBUS is 5V, but not when VBUS is 5V, So I want to disable 9V VBUS through modify the 2st bit and 3st bit of 0x02 to 0, But I found it still exist 9V sometimes. So How can I disable the 9V VBUS? I found that it must be modified before the adapter plug in from another blog, is it right? and why the VBUS will be set different value in the same situation? the follow waveform is DP and DM.

Hi Jingguo, 

Please see my comments below. 

Firstly, the BQ25890H is expected to be able to charge with either a 5V or 9V input. The voltage level of the input alone should not be what prevents charger from working normally. 

Jingguo Wang said:

So I want to disable 9V VBUS through modify the 2st bit and 3st bit of 0x02 to 0

This is correct. Setting bits 3 and 2 to 0b will disable high voltage adapter handshake. They will need to be set before an adapter is plugged in and I also recommend disabling the watchdog timer (REG07[5:4]) to ensure the bits do not reset to default.  With these bits set to 0b the BQ25890H will not attempt to negotiate the input adapter to a higher voltage. 

Jingguo Wang said:

and why the VBUS will be set different value in the same situation?

Can you please provide the same waveform showing VBUS, D+, and D- for case where VBUS stays at 5V? I will need to compare the 2 waveforms to determine why.

Best Regards,

Garrett

Hi Garrett

add more detail in email.

BR

Jingguo