BQ25792: BQ25792 Not Charging

Hi Swengwoo,

Unless the converter is in HiZ mode, the converter still operates, even after charge termination, and provides a voltage on SYS.  If there is a load on SYS, the converter will drop input current.  Can you enable the ADC, read all registers and provide those registers values to me?

Regards,

Jeff

BQ25792.pptx

HI

I will provide you with all the register values you requested. Additionally, the device outputs 5V at 0.22A, which causes some heat to be generated.

Also, there is no SYS load.

Hi Swengwoo,

I do not see any errors in registers.  I expect some input current and converter switching to keep the SYS voltage slightly above the battery voltage but ~230mA is a bit high.  If you EN_HIZ mode, does the VBUS input current drop to zero? If you disable PFM mode in REG0x12, does the input current reduce?

Regards,

Jeff 

HI.

In EN_HIZ mode, the input current drops to 0 and disabling PFM mode causes the input current to increase.

Hi Swengwoo,

I just tested on an EVM and I don't see more < 10mA going into VBUS with your configuration.  So, something is loading the output side of the converter. When EN_HIZ=1, was the battery discharging any current to SYS?  If you remove input power and power, what resistance does a DMM measure from SYS to GND?  from PMID to GND? Do you have an EVM that you can repeat the test on? 

Regards,

Jeff

HI

When EN_HIZ is set to 1, there is no discharge. The SYS-GND measurement continuously varies between 3M and 20M. We only have boards that we have personally manufactured. 

Hi SW,

The BATFET has a diode that allows current flow from BAT pin to SYS pin all the time.  I suggest you order an EVM and test on the EVM.

Regards,

Jeff

HI

After completing the charging process, the system is not load , but it appears that current is still flowing through SW2. Is there a reason for this?

Are you asking if it is normal for such high currents to flow?

Thank you for your reply. The following is a picture of SYS current output, and when charging is complete, the current amplifies as shown. Why does this happen? (The blue line is not the measurement.)

Hi SW,

I have not seen that type of waveform before.  I do not know what is happening here.  Something is loading SYS.  If you don't have a load on SYS and charge is disabled or terminated, then the IC itself is sinking current, which means it is damaged.  Can you remove the IC and place on an EVM to test whether it is damaged?

Regards,

Jeff