BQ76942: Applical issue.

Reed

Part Number: BQ76942

Hi team,

When using the BQ76942 AFE, there will be a random phenomenon of abnormal disconnection and recovery of the charging and discharging MOS controlled by CHG and DSG during charging and discharging. During this period, the software did not actively send a disconnection command. During debugging, it was found that when this phenomenon occurred, a short circuit fault (SCD) was falsely reported and the MOS was cut off. Subsequently, the short circuit protection (SCD) configuration for AFE and all protection function configurations for AFE were turned off, but this phenomenon still exists. Is this BQ76942 AFE not allowed to charge and discharge simultaneously? Or under what conditions can charging and discharging be carried out simultaneously?

9 months ago

0 Maxwell Verboncoeur 9 months ago

TI__Genius 16010 points

Hi Reed,

Could you share your register settings for analysis?

Regards,

Max Verboncoeur

0 Jacket Yellow 9 months ago in reply to Maxwell Verboncoeur

Prodigy 110 points

Hi, the register serrings about FET are as follow：

REG_FET_ENABLE(0x0022) = 0x01；

MEM_FET_OPTIONS(0x9308) = 0x0E；

MEM_ENABLED_PROTECTIONS_A(0x9261) = 0x00；

MEM_ENABLED_PROTECTIONS_B(0x9262) = 0x00；

MEM_ENABLED_PROTECTIONS_C(0x9263) = 0x00；

MEM_CHG_FET_PROTECTIONS_A(0x9265) = 0x00；

MEM_CHG_FET_PROTECTIONS_B(0x9266) = 0x00；

MEM_CHG_FET_PROTECTIONS_C(0x9267) = 0x00；

MEM_DSG_FET_PROTECTIONS_A(0x9269) = 0x00；

MEM_DSG_FET_PROTECTIONS_B(0x926A) = 0x00；

MEM_DSG_FET_PROTECTIONS_C(0x926B) = 0x00；

Regards,

Jacket Yellow

0 Maxwell Verboncoeur 9 months ago in reply to Jacket Yellow

TI__Genius 16010 points

Hi Jacket,

Could you confirm that the registers are being properly written by reading back their contents? It seems like there may be an error when writing the settings if the device is still triggering SCD. You can also submit a logic analyzer capture for us to check as well.

Regards,

Max Verboncoeur

0 Jacket Yellow 9 months ago in reply to Maxwell Verboncoeur

Prodigy 110 points

Hi Max,

This may not be caused by SCD, as after turning off SCD protection, in the working condition of charging and discharging at the same time, the DSG FET will still be randomly disconnected without sending the disconnection command, and this problem does not exist when charging or discharging separately.

0 Maxwell Verboncoeur 9 months ago in reply to Jacket Yellow

TI__Genius 16010 points

Hi Jacket,

Could you share your schematic for us to check?

If you haven't already, I recommend also taking a look at the Parallel Paths with the BQ76952 Battery Monitor Family application note to see if there is a consideration that hasn't been made in your design.

Regards,

Max Verboncoeur

0 Jacket Yellow 9 months ago in reply to Maxwell Verboncoeur

Prodigy 110 points

Hi Max,

I had found the reason yesterday, the FET status register(0x7F) provide me with wrong status while DSG and CHG FET is not being changed, so I send wrong value to set the FET control register(0x0097) based on FET status register. I am not sure if the FET status register is sometimes incorrect due to software IIC communication errors or it has actually changed.

Best regards,

Jacket Yellow

0 Maxwell Verboncoeur 8 months ago in reply to Jacket Yellow

TI__Genius 16010 points

Hi Jacket,

It sounds like an error with the communications. Have you checked the signal coming into the host-processor to see if there is any error when receiving the FET status register. The best way to do this is with a logic analyzer. You can also submit the logic analyzer capture for me to review.

Regards,

Max Verboncoeur

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BQ76942: Applical issue.