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Original question:

BQ76952: BQ76952

BQ76952: BQ76952 short test

Star Xu
Genius 9645 points
Part Number: BQ76952
Other Parts Discussed in Thread: CSD19536

Hi 

The customer design with BQ76952, After short-circuit protection, the short-circuit current is 1300A. SNESE resistance is two 2mΩ in parallel.

After short-circuit protection, the MOS cannot be completely turn off. The circuit is still discharging.

The discharge MOS drive circuit uses an acceleration circuit.

Attached the schematic for your reference.

Please give some suggestions.

Thanks

Star

  • 0
    TI__Guru 54715 points

    Hi Star,

    The CSD19536 Pulsed Drain Current IDM abs max is 400 A , so with 3 FETs 1300A would have exceeded that for one or more of the FETs.  So i may be that the FET array simply can't take the current from the battery.

    Another possibility is the switching is too slow.  Turn off current is provided by Q28 and limited by R135.  A smaller R135 would allow faster discharge.

    Control of Q28 is provided from DSG through R130, R132, R133, and R129.  R129 is the largest value and might be adjusted for faster control of the Q28 gate.  

    DSG is pulsed to a value below LD, so be sure LD represents the PACK+ value.  The behavior of DSG is fixed, if not suitable for the design you will need an external driver.

    Another consideration is how fast the BQ76952 responds to the SCD.  Consider a lower delay and threshold if possible so that the current does not build to the high value.