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BQ27Z746: Authentication related question

Hailiang Zhang
Expert 4725 points
Part Number: BQ27Z746
Other Parts Discussed in Thread: BQKEYPROGRAMMER

Hi Team，

1. The customer's battery pack prototype has been shipped, and they want to know what is the default key inside the fuel gauge?

2. How to program the key to the gauge through the host/MCU. Please provide a process guide or share a guide file? Thanks

regards，
HL

  • 0
    TI__Prodigy 290 points

    Hi Hailiang,

    1. There is no default key stored on the battery gauge, in order for authentication to work, a key must be programmed into the gauge.

    2. Is the customer trying to program the authentication key in flash or secure memory?

  • 0 in reply to Kipp Hayes
    TI__Expert 4725 points

    Hi Kipp，

    Secure memory seems better. What is the difference between Secure memory and Flash? Or what are the disadvantages of programming to Flash? The customer's current purpose is to make up for the problem of not programming the Key in the battery factory. Later, customers are also considering using hosts to program keys. So please share both ways if you can.

    Thanks

    Regards,
    HL

  • 0 in reply to Hailiang Zhang
    TI__Prodigy 290 points

    Hi Hailiang,

    Programing into the flash means the key will be in the .srec, this shouldn't be a problem for your customer unless they use a separate pack maker for the battery pack. Some packmakers dont want the liability of having access to the key, this is also the easiest way to program the key and the process is detailed in the BQ27z746 TRM in section 10.2.2

    For secure memory programming, this will prevent a separate pack maker from having visibility to the key. However the implementation of this is currently tricky. Currently the customer has to sniff the I2C line while programming a gauge using BQKeyProgrammer with their key and then replicate this process in their production environment.

    For most cases programming into the flash will be ok unless the run rate is in the 10s of millions a year.