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TCA9545A: About i2c timing issue for tvdL(Data)

GW
Intellectual 2370 points
Part Number: TCA9545A

Hi, Team

Our customer use TCA9545A and have a i2c timing issue and needs TI to clarify:

From the official i2c spec page 44(https://www.nxp.com/docs/en/user-guide/UM10204.pdf), the tVD;DAT is 3.45uS for Standard mode, and 0.9uS for fast mode)

But from TCA9545A datasheet, for both standard and fast mode, tvdL(Data) is 1us, while tvdH(Data) is 0.6uS.

 

Customer use TCA9545A in i2c standard mode speed(100K Hz). And from their test waveform, the tvdL(Data) is 1.4uS.

1.4uS can match i2c spec (1.4uS< 3.45uS), but it can’t match our datasheet(1.4uS > 1uS).

Customer is confuse, their test result tvdL(Data) can pass i2c spec, but why it can’t pass TCA9545A spec?

Could u help to share any comments?

Thanks.

G.W

  • +1
    TI__Mastermind 24440 points

    Hello GW,

    I understand the confusion. The difference between what your customer is seeing (tvdL(Data) is 1.4uS)  vs what the datasheet says (tvdL(Data) is 1uS) doesn't not matter.

    This because as long as the tvdL(Data) time is larger than1us (like 1.4us) the device will be able to communicate properly and not see timing issues. 

    The tvdL(Data) time max of 1us means that any signal faster than that would cause timing problems for this device. (ex  0.5us)

    The TCA9545A actually allows for faster communication than the nxp timing requirements, creating better performance than what is described in their requirements.

    Please let me know if you have any additional questions

    regards