I2C random no Acknowledge Issue

vihang_vinayak — Wed, 22 Jan 2020 20:08:09 GMT

Hi ,

I have design a I2C hot swap circuit using PCA9617 (as a level translator for 3.3V to 5V and 5V is the Hot side on Backplane) and LTC4300-1 (At the Input Hot side of removable card). The pull up on the Hot side I2C clock and data signal is 10K and there is ferrite bead of 0.6 ohms a resistor of 33ohms in series as shown below in the figure

I have three slave on the removable card on the output side of the LTC4300-1. The addresses are 66, 24 and 25.

After Hot insertion of the removable card with Backplane board, I randomly receive no acknowledgement from the above mentioned three slaves

Can anyone help me figure out what can be the issue?

Do the above design looks good or correct?

Please let me know suggestions and opinions

Please reply

Regards,

Vihang

Re: I2C random no Acknowledge Issue

reyes — Thu, 23 Jan 2020 21:09:16 GMT

Hi Vihang,

The design is not correct for this part number (PCA9617).

For hot-swapping operations, you need a device with circuitry that precharges the SDA and SCL pins to prevent glitching data on an active I2C bus when the unpowered slave card is inserted into the backplane system. Unfortunately, the PCA9617 does not include this feature, I recommend you to switch to a hot-swappable translator like the PCA9511/12/13/14 Hot Swappable I2C Buffers:
PCA9511A: https://www.nxp.com/docs/en/data-sheet/PCA9511A.pdf

PCA9512: https://www.nxp.com/docs/en/data-sheet/PCA9512A_PCA9512B.pdf

PCA9513/14: https://www.nxp.com/docs/en/data-sheet/PCA9513A_PCA9514A.pdf

Regards,

Jose

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