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BQ40Z50-R1: bq40z50-r1 Short circuit double pulse problem

Alexander Burtakov
Intellectual 750 points
Part Number: BQ40Z50-R1

Hello to TI support team ,

        I have problem with additional pulse from discharge pin bq  during short circuit connection at battery output .(according to scope figure ) 

 I tried different parameters set  for short circuit threshold 1 & 2 . RSNS '1' and RSNS '0' .

1. Sometimes additional short pulse appear during short permanent short circuit and sometimes at first short contact .

B.R

Alex Burtakov

  • 0
    TI__Mastermind 24870 points

    Hello Alexander,

    Can you share your schematic with us? We measured these on our EVM and do not see these spikes, if you look, even on the falling edge, there seems to be something driving up the DSG pin.

    I suggest you cross check what's on the DSG pin path on your schematic vs. the TI EVM to see if there is a difference between the circuits.

  • 0 in reply to Kang Kang
    Intellectual 750 points

    Hello Kang Kang , thank alot for your quick response.

        Design is same to EVM ,   My cells pack that connected to BMS (40z50-r1) is high enery pack 4S6P (IR~50mohm) can deliver more than 300A .

    1. Is it possible some harm to internal AFE comparator  ( r=1mohm * 300A = 300mV ) according datasheet maximum 200mV ?

    2. Can i use 500uohm Rsense ?

    3. According to internal logic of bq40z50-r1 , if Short circuit discharge threshold #2 is happens earlier that threshold #1 ,threshold #1shouldn't make turn on off again ? How I can disable at all threshold #1 or #2 operation .

    4. Is it possible disable turn on/off Fets under permanent short circuit ? I mean according technical reference Fets will turn on / off according to internal timer even if contacts are shorted  and it can harm my FETS due to high short current turing Fets transition .

    Thanks Alex Burtakov .

  • 0 in reply to Alexander Burtakov
    TI__Mastermind 24870 points

    Hello Alex,

    1. Yes, please do not exceed the datasheet maximum between SRN and SRP.

    2. It depends on your idle current. If you reduce the Rsense to 0.5 mOhm, 1 uV of noise is 2x as big as if you were to use 1 mOhm. 1 mOhm is the datasheet recommended unfortunately.

    3. You can have FET_EN bit off. You can toggle this with FET_EN command.

    4. See question 3, or you could just bypass the FETs in general and not populate the FETs.