Inquiry about PCA9617A I2C Isolation IC Design and Compatibility

[fps]

I am currently designing an external I2C communication module with an I2C clock frequency of 100kHz and I am considering using the SI8600 IC for I2C isolation.

However, I am running into a situation where the bus capacitance of the target product used for communication may exceed 400pF.

In addition, I am considering adding an I2C bus repeater or buffer, such as the PCA9617A, to the B-side of the SI8600, which is capable of handling capacitance up to 4000pF at low speeds, thus potentially solving the problem of the product bus capacitance exceeding 400pF. However, I realized that there were certain design constraints and parameters that needed to be considered, such as VIL, VIH, VOL, and so on.

With this in mind, would it be feasible to connect the B side of the SI8600 to the A side of the PCA9617A? If this is feasible, can the PCA9617A be used to output I2C to a product that needs to communicate, and if this is a viable solution, can you provide guidance on the appropriate pull-up resistor values for the A and B sides of the SI8600 and the B side of the PCA9617A?

[diazmarin09]

Hello fps,

I hope all is great with you. Thank you for using the NXP communities.

PCA9617A A side is regular I2C interface which has VIL = +0.3VCCA (max). Therefore, if you connect the SI8600 B side to the PCA9617A A side, I do not see any potential issue.

In the other hand, please keep in mind the VOL offset from the PCA9617A B side. As we know, the PCA9617A B side (SCLB/SDAB pins) has offset voltage at VOL, and it requires VIL below 0.4V to be able to detect Low level at B side.

The following pull-up resistor value should be fine. Anyway, I do recommend to perform you own tests.

I hope this information helps.

Regards,

David

[fps]

I hope this message finds you well. I would like to express my gratitude for your assistance thus far.

I have an additional inquiry regarding the PCA9617A and its capabilities. I am currently working on an external I2C communication box that connects to a computer on one end to run GUI software, while the other end connects to a product via approximately 20cm of electrical wiring. Therefore, hot-swap functionality is a necessity for my application.

Upon reviewing the PCA9617A datasheet, I did not find any mention of hot-swap support, which leaves me uncertain about its suitability for my needs. If the PCA9617A is not suitable for hot-swapping, could you possibly recommend an alternative model that would accommodate this feature?

Thank you for your time and assistance.

[diazmarin09]

Hello fps,

Thank you for using the NXP communities. It is our pleasure.

I am pleased to know that the information provided was useful for you.

Correct, the PCA9617A device does not feature the hot-plugging.

Have you considered the devices below?

PCA9511A - Hot Swappable I²C-Bus and SMBus Bus Buffer

PCA9615DP - Two-Channel Multipoint Fast-Mode Plus Differential I²C-Bus Buffer with Hot-Swap Logic

I hope this information helps.

Regards,

David