BQ76952: BQ76952 MOS can not open after 40A discharge

Star Xu

Part Number: BQ76952

The customer design with BQ76952, the battery is connected to the inverter, and the inverter is loaded for a 40A discharge.

When a fault occurs, the MCU sends a command to BQ to cut off the charge and discharge MOS, and then controls DFETOFF (configured to turn off the charge and discharge MOS) and makes BQ enter SHUTDOWN mode, and the battery has no output.

When the battery is turned on again, there is no output from the battery.

Attached the register setting and schematic.

Safety Alert A is 0x00

Safety Status A is 0x00

Safety Alert B is 0x00

Safety Status B is 0x00

Safety Alert C is 0x00

Safety Status C is 0x00

PF Alert A is 0x00

PF Status A is 0x00

PF Alert B is 0x00

PF Status B is 0x00

PF Alert C is 0x00

PF Status C is 0x00

PF Alert D is 0x00

PF Status D is 0x00

battery status is 0x80

Stack Voltage is 0x12BD

PACK Pin Voltage is 0x0014

LD Pin Voltage is 0x0013

Alarm Raw Status is 0x0683

Internal temperature is 0x0CEE

SCHEMATIC1 _ P04_FETDrive.pdf

Please help check it.

Thanks

Star

over 1 year ago

0 Max Verboncoeur over 1 year ago

TI__Mastermind 25980 points

Hi Star,

Could you check 0x0057 MANUFACTURINGSTATUS [FET_EN] to see if it is low? If it is low then sending the FET_ENABLE() command will set that bit high and bring the device out of FET Test Mode.

It's worth noting that exiting SHUTDOWN mode will cause the device to reload its default or OTP programmed register settings. If any changes to the register settings were made before entering SHUTDOWN mode, they will not persist after exiting SHUTDOWN mode unless they are programmed into the OTP.

Regards,

Max Verboncoeur

0 Star Xu over 1 year ago in reply to Max Verboncoeur

TI__Genius 9645 points

Hi Max

Thanks for your reply.

0x0057 MANUFACTURINGSTATUS is 0x0050 [FET_EN] is high

FET Status shows that the charging and discharging MOS is closed. The DSG FET =1 is on. The CHG FET=1 is on.

Waiting for your reply.

Thanks

Star

0 Max Verboncoeur over 1 year ago in reply to Star Xu

TI__Mastermind 25980 points

Hi Star,

Have you tried probing around the FETs to see if they are turning on properly?

Regards,

Max Verboncoeur

0 Star Xu over 1 year ago in reply to Max Verboncoeur

TI__Genius 9645 points

Hi Maxwell

Thanks for your help.

After cross-testing they find the chip was damage.

Could you please help check the schematic and the parameters?

Thanks

Star

0 Max Verboncoeur over 1 year ago in reply to Star Xu

TI__Mastermind 25980 points

Hi Star,

Were any abs max ratings exceeded on the device? Have there been multiple IC failures with this design or has this occurred with just one IC?

Also, I recommend taking a look at Figure 5-2 of the Multiple FETs app note. D4 and D5 on that schematic are necessary for the BJTs that you use in your schematic to turn on properly.

Regards,

Max Verboncoeur

Power management

Power management forum

BQ76952: BQ76952 MOS can not open after 40A discharge