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SMbus connection for bq20z65

swapnil dadhe
Prodigy 145 points
Other Parts Discussed in Thread: BQ20Z65

Hi,

This is in reference to the recommended circuit design for bq20z65. The reference design suggests two 100ohms resistances in series with the SMbus data and clock lines. However the SMbus 1.1 specifications suggest direct electrical connection between the host and the slave using two pullups to 5v and no series resistances.

1>Should the SMbus lines be externally pulled up ?

2>Also my host is micro controller running on 5v , how should i connect it to the SMbus lines ?

 

Thanks in advance.

  • 0
    TI__Genius 10235 points

    The two series 100 Ohm resistors are used for ESD protection. They have been tested and verified to not significantly effect the transmission of the clock or data on the bus. 

    The SMBus lines should be externally pulled up with a 10K pullup.  Also, you can plug your 5V directly to the SMBus lines.  The gauge transmits at 3.3V volts, but can receive 5V just fine. The abs max that can be transmitted to the gauge is 6V.