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TMP117: TMP117 tf-SDA spec

Kai Nomiyama
Expert 5605 points
Part Number: TMP117

Hi Team,

I have a question about tF - SDA spec.(datasheet page7, 6.7 Two-Wire Interface Timing).
tF - SDA min spec is defined as 20x(V+/5.5).

Do we also have to meet this spec when master sends I2C data to TMP117?

Regards,
Kai

  • 0
    TI__Guru* 91206 points

    Dear Kai - 

    Thanks for posting - this specification value detail is identical to the I2C standard for Fast Mode and would apply to both the Master and the Slave device, when running in Fast Mode, however, there are notes on this spec line item, which state that device must give at least 300nSec of hold time for the SDA. I am not sure in what scenario you would not be able to meet this requirement, when using controller which has built in I2C block and any pullup or series protection resistor that were correctly sized. See tables 9 and 10, and their associated notes, here: https://www.nxp.com/docs/en/user-guide/UM10204.pdf

  • 0 in reply to Josh Wyatt
    TI__Expert 5605 points

    Hi Josh,

    I have two questions about the link so could you help?

    Question 1
    There is no tf-SDA min spec of standard-mode but when I2C data is standard-mode like 10kbbs, is tf-SDA min valid?

    Question 2
    how much load capacitance TMP117 supports?
    from the link, when we use pull up resistor with Fast-mode, if load capacitor is less than 200pF, it looks no problem but is it ok to apply this to TMP117?

    Regards,
    kai

  • 0 in reply to Kai Nomiyama
    TI__Guru* 91206 points

    Dear Kai - 

    A1. I have not seen any issues come through the Forum or from direct customers using standard mode with the TMP117. 

    A2. The TMP117 has 4pF of input cap on the digital lines. The I2C spec max on the bus is 400pF, however if you calculate Rp(min), you might find that your actual circuit limit may be less than that and if you measure the bus itself, that is even better and you are not even close to a limit. This is especially true on a PCB. in the link to the I2C spec in previous post, check out section 7, page 55.