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BQ76940: BQ76940 Over current and short circuit are not protected

chunqiu lv
Intellectual 715 points
Part Number: BQ76940

HI TI Team:

Customer BMS use BQ76940 to Balance&protect, Find not protect when debug ,The set status as follows:

1.The sampling resistor is connected in parallel with four 5mR resistors,calculated resistance value is 1.25mR

2.Set sys_ctrl1 0x04 register   0X18,sys_ctrl2  0x05 register 0X43, protect1  0x06  register 0X12,protect1  0x07  register 0X23,

3,After the register value is written in, when it is read out, the data can be mapped

4.Short circuit the load and read 0x00 register value as 0x80,this No SCD fault is detected. 

5.Adjust the load so that the discharge current value is greater than the design value,read register 0x00 value is also 0x80,thisNo OCD fault is detected.

Please help me

Thanks

CQ.LV

  • 0
    TI__Expert 5090 points

    Hi CQ,

    Our expert on this device is on vacation right now, I can comment based on my limited understanding of the device.

    I did not see an issue with your settings.  You don't mention the PROTECT3 register (0x08), if the four RSVD bits are not set to zero, it may affect the SCD voltage threshold.

    What voltage is being generated across the sense resistor when you create the short circuit or over current condition?

    Thanks,

    Terry