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TMP431: TMP431 SMbus has fixed only one address.

Pradeepkumar Selvaraj1
Prodigy 180 points
Part Number: TMP431
Other Parts Discussed in Thread: PCA9548A,

Hi,

I wondered after checking datasheet of TMP431D, that it has only one Address fixed for its SMBus 1001101b ???

How many TMP431D devices can be connected on a SMBus?? If so, please specify the different address..

How can I connect more than two TMP431D devices in a SMbus??? Please clarify

Thanks

Pradeep. S

  • 0
    TI__Mastermind 38590 points

    Hello Pradeep,

    The TMP431D uses a fixed address.  We also offer the TMP431A and TMP431C which use a different fixed address allowing you to have 2 devices on the same bus.  If you needed to have more devices on the bus, you could consider an I2C mux like the PCA9548A which would allow for up to 8 devices that all have the same address.

  • 0
    TI__Mastermind 35855 points

    TMP431D only has one I2C address, so you cannot have two TMP431D on the same bus. TMP431C and TMP431D both have the default therm limit of 0x69 which is different from other TMP431 models. If you wanted two TMP431D's on the same bus, you would want to buy both a TMP431C and a TMP431D.

    thanks,

    ren

  • 0 in reply to Ren Schackmann
    Prodigy 180 points

    Thank you Ren & Eddie.

    Also, from the datasheet the minimum required current levels for SMBus lines is specified as minimum SMBus output low sink current as 6mA & Logic input current as 1uA.

    Which value I should consider for calculating SMBus pullup resistor values??

    Please clarify..

    Thanks

    Pradeep. S

  • 0 in reply to Pradeepkumar Selvaraj1
    TI__Mastermind 35855 points

    SDA VOL is specified with 6mA sink. That is the max current for calculating minimum pull-up resistor value. Pull-up resistor size is only a concern for our output. Our other pins do not act as output, and all inputs have this input leakage of less than 1uA. 

    ren

  • 0 in reply to Ren Schackmann
    Prodigy 180 points

    Hi Ren,

    Thanks for explaining. Still I cant understand it clearly. sorry..

    As you have mentioned 6mA sink is the max current to calculate minimum pullup value, then the minimum required value R value becomes around 550ohms. The maximum it can go in 4.7k or above kohms.

    Is it means, beyond 6mA it will damage the open drain logic in the chip??

    Sorry if my question seems fundamental one..

    Please clarify

    Thanks

    Pradeep. S

  • 0 in reply to Pradeepkumar Selvaraj1
    TI__Guru* 90906 points

    Pradeep -

    As Ren mentioned, the specification (I2C) makes the requirement of 6mA at 0.6VOL  or 3mA at 0.4VOL and this is to drive a full bus load at 400kHz clock speed). This part is just designed to meet the spec limits, which are calculated from possibilities that circuit combinations may present. 

    There is a section of the I2C spec which discusses this topic.