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TCA9406: TCA9406 vs PCA9306 - whats the difference?

Marks Greulich
Intellectual 540 points
Part Number: TCA9406
Other Parts Discussed in Thread: PCA9306,

Hi,

I`m searching a I2C levelshifter from 1,95V to 5V Logic. I have found that two guys but I dont see the huge difference between them. Ok one has internal pullups what is good to have. 

2ndly I have to ask what happens in the following case: VCCA is 1,95V. VCCB is 5V. What happens if the logic high on the A-Side is only 1,8V? Are there any high cross currents what I have to consider? 

Thanks & best regards,
Markus

  • 0
    TI__Guru 72821 points

    "Ok one has internal pullups what is good to have. "

    Only when the device is enabled though.

    "What happens if the logic high on the A-Side is only 1,8V?"

    You mean when you have VccA set to 1.95V but pull ups on SDAA and SCLA are 1.8V? This shouldn't be an issue for PCA9306 but TCA9406 may try to yank the 1.8V logic up to whatever VccA is set to (1.95V in your case assuming I interpreted the question correctly).

    "Are there any high cross currents what I have to consider? "

    There would be for TCA9406. The main difference between the two devices is the TCA9406 has a rise time accelerator which very quickly drives the signal high and generates a large di/dt so you may see crosstalk if the traces are too close. The TCA9406 is better suited for 1MHz I2C while PCA9306 can support 400kHz and does not have that rise time accelerator. I can see the rise time accelerator being overkill in some situations and can cause itself to trigger if VoL is too large and there is crosstalk/bouncing on the signal which could cause signal integrity concerns. I would suggest PCA9306 if you don't need the 1MHz speed support.

    Thanks,

    -Bobby

  • 0 in reply to BOBBY
    Intellectual 540 points

    Hi Bobby,

    thanks a lot - that helps. Ur right - I dont need fast edges and I can set my clk to a low kHz range so I dont wanna gain trouble cause of x-talk and reflections. 

    PCA9306 is my choice now. 

    BR,

    Markus