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BQ24005 not working - parts being damaged after power up

Joao Martins
Prodigy 20 points
Other Parts Discussed in Thread: BQ24005

Hi

I have 2 BQ24005 damaged after I power up the PCB.

R2=11.5k and R3=40K (my thermistor is a 10K).

After burning the first sample I populated a second board and I powered it up without the battery connected. I observed a very low power consumption and the timeout (pre-charge) correctly. Then I inserted the battery and the LED D2 light up and the current observed matched the one expected (aprox 1A).

Then I power down everything and with the battery inserted I power up the circuit again. From that moment on the second BQ24005 got burn also.

Any idea/ advice?

Thanks

Joao Martins

  • 0
    TI__Mastermind 32400 points

    Hi Joao,

     

    Can please provide us with some scope captures during the start up with the battery inserted? We need to understand what causing the burn out of the part. any info on the following pins will be helpful

     

    ·         Vbat, I bat, Iin , Vin,Vsense, CR, APG/THM, VSEL?

    ·         The status of STAT1 and STAT2 during the start up.  

    What the status of S1 during start up? Open or closed? Supposed to be closed and the pin should be connected as close as possible to the Battery.  Also I recommend 10uF cap between BAT+ and BAT- as in the EVM design. Can you please verify the values of R1 and R2 as on page 14 from the data sheet?   

     

    Thanks!

    Tahar

  • 0 in reply to Tahar Allag
    Prodigy 20 points

    Hello Tahar

    thanks for the reply.

    I will not be able to get some scope captures for a couple of days as I'm out of the office until the beginning of June.

    By that time I will send you some screenshots.

    In the meantime I'm able to answer some questions:

     - The S1 Switch was open during start-up

    - S1 is very close to the battery and charger (please see part of the PCB layout bellow)

    - There is a 10uF + 100nF + 100pF on the Vcgh input and there is a 10uF  + 100pF between BAT+and GND . After the Switch there is some more decoupling caps for a MCU, etc

    - The R1 and R2 that you mention on my sch are named R2 and R3 if I understand correctly and the values are: R2=11.5k and R3=40K (my thermistor is a 10K).

     

    I'm running out of parts (I only got left 2 parts), but I will try to get the screen captures when I return to the office.

    Thanks 

    Joao Martins

  • 0 in reply to Joao Martins
    TI__Mastermind 32400 points

    Hi Joao,

     

    You can order samples online for free using the following link:

     

    http://focus.ti.com/docs/prod/folders/print/bq24005.html#samples

     

    And use Sample & Buy on the top right of the screen.

     

    Can you try closing S1 and see if that makes any changes on the behavior of your circuit?

     

    I will be out of office the first and the second week of June. I will forward your question to someone else.   

     

    Thanks!

    Tahar