TCA9517-Q1: Communication distance

What I2C frequency are you trying to support?

What is the Vcc level you are trying to support?

Do you have control over the two boards (the main transmission board and the receiver board)?

Are you going to be using any other I2C buffers in either of the boards? 

-Bobby

Hello Bobby,

We need the solution of I2C buffer, this buffer will be adopt in distance detection function for face recognized.

Hello Bobby,

Frequency and VCC are not the point. this application need the low power, stanblized, 2 meters transmission.

To me it seems like you're asking for a potential device for an I2C buffer across cables, if this is true then I would need to know what I2C frequency you need to support and Vcc level you would need to support to provide a solution. Me suggesting a TCA980x for example would not be able to support a 5V signal nor 1MHz support. TCA9517 technically doesn't care about the cap loading but it's prop delays may not help support the frequency you need. Also if you want to get more noise immunity on the harness side then using a 5V Vcc line would not be as robust as a 12V line. 

For a balanced noise rejection solution for example, you could use a P82B96 paired with a CAN transceiver to make a more robust cable transmission line but at the same time, this doesn't support I2C spec in the 400kHz range, this is why I asked those questions. Suggesting any solution with an I2C buffer but only on one side would defeat the purpose of trying to buffer the line if you can't place buffer on both sides of the signal which is why I asked about design control over both boards.

Using other I2C buffers on either board also spells trouble due to static voltage offset rules which makes designing I2C systems tricky which is why I asked the last question. If I told you to place TCA9517 with A sides facing each other on the cabling end but you have another static offset buffer on either side of the cabling, the you would end up potentially causing oscillations on the I2C bus due to the incorrect I2C buffer configuration. To avoid this, I would need to know if there are any other I2C buffers in your system. 

The short answer to your question is yes TCA9517 can be used to buffer a 2 meter cable. But there are other concerns outside of this which you would need to plan for and can make designing a system like this difficult.

-Bobby

Hello Bobby,

thanks for your answer,the frequency is about 400k, and the VCC is 3.3V, according to your experience, is it should be 12V?

Usually the 12V choice is used in a high electrical noise environment such as factory automation. Using higher Vcc does help with noise margins if you're expecting noise to be a problem but not always necessary.

Using a 3.3V line would be better for you if you're goal is to lower power consumption. TCA980x may be an option as well as it is technically lower power than TCA9517 but it has a deglitch mechanism which might cause issues with cable transmission. I would suggest trying TCA9517 first with A sides facing the cable. TCA980x is pin to pin with TCA9517 so you could also try TCA980x if you remove the pull up resistor on B side as well. 

-Bobby