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BQ78Z100: Questions about the BQ78Z100EVM schematic

Gary Wang1
Intellectual 350 points
Part Number: BQ78Z100

Dears,

compared with the SCH from BQ78Z100 datasheet and EVM, there is a diode(D1) in BQ78Z100EVM, and I want to know why, what happens if i do not use the diode.

thanks.

  

  • 0
    TI__Guru* 76230 points
    Hi Gary,
    The diode is to protect the pack pin. You can leave it out if you are sure you will not have reverse charger connection.
    thanks
    Onyx
  • 0 in reply to Onyx Ahiakwo
    Intellectual 350 points
    Hi Onyx,
    get it, my understand is that the diode is used to protect pack pin, but not reverse protection, still need to add MOSFET 2N7002 to realize reverse protection function, so the diode and MOSFET should be able to use at the same time? and whether the diode affects the monitoring voltage of pack pin?
    thanks a lot.
  • 0 in reply to Gary Wang1
    TI__Mastermind 34665 points
    Hi Gary,

    Yes the diode is to prevent current draw from the gauge via the PACK pin if the PACK is shorted or reverse biased (as Onyx mentioned). You will still need the MOSFET protection for reverse biased connection on the PACK+/PACK- pins. There will be a drop across the diode, but wouldn't impact PACK Voltage detection. You can minimize the diode voltage drop by using a Schottky type diode.