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I2C Level Shifting

Marcel Schenker
Prodigy 50 points

Other Parts Discussed in Thread: TCA9617B, PCA9306

Hi folks,

I have an existing electronic with a TCA9617B and a I2C voltage level of 3.3V. I need to shift this 3.3V logic level down to 1.8V. As it is not possible to connect two B-sides of TCA9617B together I cannot use this device for my application.

Is it possible to use the PCA9306DQER for this voltage level translation? What about the pedestal of TCA9617B? I cannot find a value for low level threshold in the datasheet of PCA9306DQER?
Are there any other suggestions to solve this problem?


Thank you.

  • 0
    TI__Expert 5140 points

    Hi Marcel,

    Thanks for the question. I've drawn up two possible solutions to this issue (below):

    1)

    With this solution, you could parallel two TCA9617B devices in order to get the 1.8V logic level and would avoid connecting the B sides of the TCA9617B.

     

    2)

    Another solution is what you previously mentioned in your post, which would be to use the PCA9306 after the TCA9617B. The problem that I can see occurring from this setup is that the VOL offset of the TCA9617B would not translate well over the PCA9306 when shifting back to 1.8V. This is because the VOL limit of the PCA9306 might be violated due to the offset produced by the TCA9617B. With this concern in mind, it may be better to go with option 1.