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bq27541 unused pin termination

Patrick Marshall
Intellectual 310 points
Other Parts Discussed in Thread: BQ27541, BQ27541-V200

An customer is using the bq27541 in a reduced capacity, and wants to know how to safely tie off the following unused pinss:

 

BAT(4)

SCL(11)

SDA(10)

SRN(8)

SRP(7)

TS(9)

I'm guessing I2C can be Vcc because they recommend pull-ups, but am not readily sure what to tell him about the analog pins. Can anyone help?

thanks!

  • 0
    Intellectual 310 points

     

    Additional customer inquiry for bq27541-V200 as follows:

    = = = = = = = = = =

    Another thing that is unclear is how the host diferentiates between its own authentication engine and the one in the peripheral.

     

    Is the host responsible for comparing the resulting answers from the host side and peripheral side?

     

    If the data lines (HDQ pins)are common to both the host and peripheral authentication engines, how does the host microprocessor identifiy which one it is initiating the authentication process with?

    = = = = = = = = =

    Any guidance is appreciated!

  • 0 in reply to Patrick Marshall
    TI__Expert 4050 points

    Not sure what customer want to do. From safety prospective, SCL, SCA can be pulled high and SRN/SRP can be tied to ground. TS can be tied to ground with 10k.

    host should comparing the response. Host need read the response from gauge and compare.

  • 0 in reply to Patrick Marshall
    TI__Genius 14985 points

    HDQ is a single-master/single-slave protocol that has no device addressing capability. 

    The host should generate a random challenge for the peripheral and send it over HDQ to the bq27541.  It reads the response, then will internally compute its own response and compare the two to authenticate.

    If the host lacks the horsepower to do the computation, or the secure memory or engine to do it, they can also buy two bq27541 for the price of two.  One can go in the peripheral and the other "trusted" one can go on the host board, but they will need to use separate buses.  Two pins for two HDQ buses, or one HDQ and one I2C, or two separate I2C buses since they will have the same I2C address.

    I would recommend tying BAT to VCC or REGIN.