BQ25890: BQ25890

Hi Xiong,

1) Can you provide a full register dump from the BQ25890 when VBAT (voltage at the BAT pins of the IC) is at 2.8V? Can you also provide a register dump when VBAT is measured at <2V?

• When the voltage at VBAT is measured as 2.8V, the charger should be in Pre-Charging state
• When the voltage at VBAT is measured <2V the charger should be in BATSHORT state (Charging with I_SHORT, given a valid input)

2) Can you provide a scope capture that shows VBUS, IBUS (input current), VBAT, and IBAT (charging current)?

• What is your SYS load current, if any?

Regards,

James

Hi, James.

Thanks for your helps.

here is the reply to your question:

1) How to get the full register dump from the BQ25890? What's the command we can get it from the I2C protocol?

2) the unit is Andriod12 platform and we set the power off voltage is @3.0.  When the voltage battery module is below 3.0, the unit will auto power off, then  how can I get the full register dump from the BQ25890? In he two situations as blow, the unit can't power on.

• When the voltage at VBAT is measured as 2.8V, the charger should be in Pre-Charging state
• When the voltage at VBAT is measured <2V the charger should be in BATSHORT state (Charging with I_SHORT, given a valid input)                      

3) the input voltage will be the range for 5V to 12V, according to the PD protocol.

4) the sys load  rush current would be @3A, and the normal current would be @1.5A

Regards,

Xiong

Hi Xiong,

1) There is no specific I2C command for a register dump according to the BQ25890 programming. You will need to read every register using your I2C communication and print out each value under the conditions that I mentioned in my lest reply. A list of register values that looks like the below table would be ideal (your device should have different values, the picture below is just an example of the register list).

2) I'm not sure how the battery module shut-down you are describing relates to the state of the charger IC. The battery of your system should be connected to the BAT pins of the IC. If the voltage measured at the BAT pins of the IC is below 3.0V, by default the device should be in the pre-charge state attempting to charge the battery (assuming you have a valid input at VBUS, and charging is enabled).

The BQ25890 should not be turned off when the battery falls below 3.0V. The function of the BQ25890 is to supply power to the system while also charging the battery. If the battery falls below 3.0V, you should still have access to I2C communication, even if only the battery is connected (no adapter). If you have a valid adapter voltage connected to VBUS, I2C communication should be available regardless of the VBAT voltage.

xiong aijun said:

I found a issue, when the tablet placed a long and long time, the voltage of the battery would low down and go into the over-discharge protection @2.8V, and then the output of the battery module is 0V.

Why is your battery changing from 2.8V to 0V so suddenly? A real battery should not be able to change voltage levels quickly.

Regards,

James

Hi, James,

Can you kindly review the chip application schematic picture shown in the first page?

Is there any mistake in it?  I think I should check the hardware first. If it's right, then we can go through the issue to check the software.

thanks.

Xiong

Hi Xiong,

Please visit https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/874557/faq-bq25890-faq-bq2589x-schematic-review-and-pcb-layout-design-tips for BQ2589X: Schematic Review and PCB Layout Design Tips.

The components you have selected appear to be correct.

Regards,

James