Blown talon srx modules

[philso]

Originally Posted by Michael Hill

My guess is something thermal is happening in combination with ESD. It looks like The protection diode is only rated up to 125 Celsius, which I think is normally fine. However, when put in an enclosed box like the SRX is and put inside of a robot with potentially not enough air flow to convection cool the fins, perhaps the diodes aren't able to offer the full protection they normally would. I don't have any temperature measurements to back this up, and I'm not exactly sure how you could accurately (and easily) measure the junction temperature while simulating the SRX enclosure.

That's really my best guess at the moment.

In normal operation, those transorbs have less than 100 nanoAmps flowing through them and are essentially out of circuit. The energy present in a standard ESD test, like the ones referred to in the datasheet linked by Mr. Copioli would not contain enough energy to cause the temperature of the transorb to rise that much. It would not pass those tests if it did.

Transorbs are a pretty rugged class of devices. I have severely abused similar devices by applying surge voltage test with much higher energy than the ESD test (several 100 x), without allowing the required cool down times and the transorbs worked properly up till the heat dissipated in them melted the solder and the part fell off the board. They continued to work after we soldered the parts back in the board.