BQ76952: Body diode protection

Hello Rayvano Keizer,

Is the SLEEPCHG bit set in Settings: FET: FET Options: SLEEPCHG? If this bit is set, this will enable the CHG FET while in sleep mode.

Rayvano Keizer said:

My body diode threshold is set at 0x7FFF and there is no load connected to the battery

Body Diode Threshold is in units of mili Amps. How are you disabling the body diode protection? Please share your settings.

Are you using series or parallel FETs connection? 

Note: If the BQ76952 senses a current greater than the Body Diode Threshold, the device will turn ON the FET to avoid overheating the body diode and prevent the FET from damaging.

Regards,
Jose Couso

Jose Couso said:

Is the SLEEPCHG bit set in Settings: FET: FET Options: SLEEPCHG? If this bit is set, this will enable the CHG FET while in sleep mode

Yes, it is set

Jose Couso said:

Body Diode Threshold is in units of mili Amps. How are you disabling the body diode protection? Please share your settings.

I know it is in mA. I only disabled the body diode protection to see if this function enables my charge mosfet during a COV event. I disabled it by setting SFET to 0 (Parallel mode), but normally this bit is set to 1 (Series mode). 

Jose Couso said:

Are you using series or parallel FETs connection? 

Series.

Hello Rayvano Keizer,

If SLEEPCHG is set, try disabling it and see if the CHG FET remains OFF during SLEEP mode (no charge/discharge current detected).

Regards,
Jose Couso

The CHG mosfet is supposed to be on in sleep mode but I dont want the CHG mosfet to turn on when COV fault is still present.

When COV fault is present the CHG mosfet does turn off, but the CHG mosfet randomly turns on for 1-2 seconds and then turns off again. This repeats itself randomly.

Hello Rayvano Keizer,

Monitor the Safety Status A()[COV], maybe COV is self recovering. Check if XCHG bit is clearing in Alarm Raw Status. 

Is FET_EN() set in manufacturing status? FET_EN command() is required for autonomous FET control.



Please share a log file of this happening and the settings.

Regards,
Jose Couso

The COV is set a 3,75V and the release is set 3.6V. The COV fault remains active the whole time because the voltage does not become lower than 3,6V. But during this time the CHG mosfet randomly turn on, so the CHG mosfet turns on even when the COV is still active and the release is not even met.

Hello Rayvano,

Rayvano Keizer said:

For testing purposes I disabled the body diode protection, and now the CHG does not ramdomly turn on again.

As mentioned above, body diode protection might be causing the CHG FET to turn ON. Try increasing the Body Diode Threshold.

When the CHG FET is off, no current is flowing, but just the noise detected by the current may look like DSG above the Body Diode Threshold occasionally.  Then as soon as CHG turns on, the current is charging, and it turns it back off quickly.

Regards,
Jose Couso

It happens also when I put the Body Diode Threshold to its maximum value.

Hello Rayvano,

Please share your gg file (configurations). I would like to try your settings.

Are you using a custom board? Have you done calibration? 

Regards,
Jose Couso

Hello Rayvano,

I am glad you were able to find the problem. Make sure to test the thresholds and check they work for your application.  

Regards,
Jose Couso