TCA9517: The Best Solution to Connect I2C Bus with Different Voltage Rails

Hey Kazuki-san,

Taking a quick look at SN74CB3Q3245, this device probably isn't what you want if you are trying to re drive your I2C bus since it just uses a pass FET architecture.

It sounds like you are connecting two boards directly to each other (not using cables) is this correct?

Are the boards already powered on before connecting to each other?

Maybe a hot-swappable buffer may be a better solution like our TCA9511A.

The other option is to use an I2C switch like the TCA9544A (in this a case the SN74CB3Q3245 could also work if I am understanding correctly).

Thanks,

-Bobby

Hi Bobby,

Thank you for your help.

No. The boards are already connected before powered on. However, the each board power up sequence is independent each other.

That's why he is trying to consider I2C repeater TCA9517 for his initial thought.

It may work, but he wonders about if there's more suitable and cost optimized solution which can connect boards without sequencing concern. 

TCA9511 looks much expensive compared to TCA9517.

Does it make sense?

Regards,

Itoh

Hey Kazuki-san,

If the customer would like a cost competitive I2C buffer, then we could consider TCA980x. This device does not have power supply ramp requirement and supports 3.3V. The only requirement is that you do not have a pull up resistor/I2C switch/other static voltage offset buffers on B side of the device.

If the customer does not require a buffer, then PCA9306 in the switch configuration would be an option and our best cost competitive device.

Thanks,

-Bobby

Hi Bobby,

Thank you for your reply.

The customer does not require buffer.

What do you mean by switch mode?

Does PCA9306 support 3.3V - 3.3V communication without level shifting?

Regards,

Itoh

Hi Max-san,

Appreciate your help!

Regards,

Itoh