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BQ76952: Shutdown after short ciruit

Milos Brncal
Prodigy 10 points
Part Number: BQ76952

Tool/software:

I used your circuit form datasheet figure 16.2. If I do short circuit on the output, BQ stops I2C (maybe goes in shutdown), DSG gate has still 1V, so DSG mosfet is partially open and the output is no more protected. I must remove Batt voltage to reset this state. If I just load more than SCD is set, everythink works fine, the SCD bit is set, after 5 sweconds is cleared. 

  • 0
    TI__Mastermind 42060 points

    Hello Milos,

    Can you provide more detail on this? Did you check REG18? 

    What is the differential voltage between gate-source of DSG FET? 

    I do not quite understand what is the test condition here, a step-by-step procedure would be useful, as well as your schematic.

    Best Regards,

    Luis Hernandez Salomon

  • 0 in reply to Luis H. S.
    Prodigy 10 points
    Hello Luis,
    the voltage on reg18 is 1,8V. Gate source voltage is 0,5 ~ 0,7 V. 
    Test conditions:
    I connect the voltage, I2C start to communicate with BQ Studio, I load the gg file for BQ with settings and write it to memory (not OTP, I do not have the final values). Everythink is working. I want to test short circuit protection. I set SCD on 00 (10A) and delay 30µs. I connect to the output 2,7 Ohm resistor, witch consumes 17A. Output voltage drop immediately, register with SCD is set to high, after 5 seconds cleared to low. Great. Than I connect just banana cable on the output to do short circuit. There flies spark and BQ Studio lost data from BQ. I2C is no more running. On the output is still voltage, on the gate is under 1 V like mentioned. I must disconnect the voltage to have default settings again.
  • 0 in reply to Milos Brncal
    TI__Mastermind 42060 points

    Hello Milos,

    Do you have waveforms of this event? What is the voltage on the REG18 pin? How is there a voltage on the output if the DSG FET is OFF?

    Can you measure the gate voltage of both DSG and CHG pins and measure the PACK and BAT pins?

    Best Regards,

    Luis Hernandez Salomon