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Original question:

BQ40Z50-R2: Pack only charges, when Smbus Communication is active

BQ40Z50-R2: Short Circuit Detection does not trigger. MOSFETS blow.

Flix
Prodigy 220 points
Part Number: BQ40Z50-R2
Other Parts Discussed in Thread: BQ40Z50

 

 

Dear TI-Community,

We have massive problems with a BMS protected by a BQ40z50.

When we do a shortcircuit test the dual channel MOSFET blows, though the Protection is set. 

I will attach the .srec golden file to this Post. We tried with different parameters and for DA-Config(Non-Removable) [NR] = 1 and also [NR] = 0, but the effects are the same. 

After programming the Goldenfile, we Enable Gauge_EN, FET_EN, BBR_EN and Lifetime_En. 

I would appreciate your help and thanks in advance, 

Felix

  • 0
    TI__Mastermind 42535 points
    This is going to take me some time to check out. Please allow me a week to respond. I will mostly reply earlier.
  • 0 in reply to Batt
    TI__Mastermind 42535 points
    Please try with the following

    reset NR, set enabled protections b to 7f, reset latch limits to 1. I believe it's your 5 attempts that are causing it to blow. You can also reduce the afe threshold for scc and scd to lower than 77 if your sc thresholds are lower. if nothing works, it is probably your fets which have a high gate cap.
  • 0 in reply to Batt
    Prodigy 220 points
    Thank you very much for your detailed answer.
    The Mosfets already blew before we increased the Latch Limit, this was done just for testing purpose.
    A detailed look in the Mosfets Datasheet revealed a pretty high gate capacity in combination with poor thermal characteristics.
    So the next step is replacing the blown mosfest with pin compatible Mosfets.

    In Enable Protections B Register, your suggested modification is setting it from 0xFF to 0x7F, which corresponds to changing the highest bit from 1 to 0. But in the Technical Reference Manual there is no desription for the function of this bit and the default value is 1. I already wondered why there is a given possibility to change RSVD Bits, but they seem to have a non descripted function, we couldn't know.

    I think your answer resolved the issue. I will delete the attached files from the post.

    Thank you very much!
    Regards Felix