PCA9615 Failures

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PCA9615 Failures

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Staff
Contributor I

Hi, Forum,

The circuit below is used on both ends of a 10-foot cable.  The PCA9615 I.C.s catastrophically and permanently fail, sometimes at both ends of cable simultaneously.  Failed I.C.s drag down our power supply and get hot - they die. Replacing the I.C.s fixes the problem.

Failures may occur after hours or days of normal operation, or immediately after a disconnect/reconnect, and possible after (unauthorized) hot-swapping.  The cable carries the PCA9615 dual differential bus, ground, and +24V.  +5V and +3V are generated from +24V independently at each end of the cable.  We are not using the hot-swap logic, but have EN tied to +3.3V.  The datasheet includes no Limiting Values identified for hot-swap, and its hot-swap description mentions nothing about protecting the I.C., so I presume the hot-swap logic is intended not to protect the device from damage, but to prevent the device from corrupting data when connected to a live bus.

The failure can be recreated by intentionally hot-swapping under ESD-safe conditions, so failures are probably not likely cause by ESD.

No microcontroller is available to operate the hot-swap EN signal at one end of the cable.

Is hot-swapping without using the hot-swap logic known to cause device failures? 

What is the failure mechanism?

The PCA9615 is a nice, inexpensive, compact solution to extending I2C through a cable.  We'd like to keep using it, and we want to keep using it if possible.

Suggestions?

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aferm
Contributor I

I am having similar issues with heat and communication failure. VDD(A) = 3.3V, VDD(B) = 5V, EN = floating, no hot-swap.

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guoweisun
NXP TechSupport
NXP TechSupport

For the unused of hot swap function, floating the EN pin because of it connect with VDDA inside of IC.

 

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