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I'm using a TLP222A to switch a 24V load that never pulls more than about 200mA. My circuit looks like this, ignore that the chip name is wrong.

enter image description here

I have 4 of these connected to 4 GPIO pins. 2 of them have, for no reason I can discern, stopped working. They show 1.15V at the input, which to me implies that the diode inside is conducting normally. The GPIO seems fine. But the output is floating, like the chip is broken.

I'm confident that I did not pull more than the on state current of 500mA nor anywhere near the peak 1A. I also used 220ohm resistors to supply 10mA to the diode, which is also well below its maximum rating.

Not really sure what else to look for, here. :/

Edit: as requested, here is a link to one of the industrial LEDs I am driving. This is the load. There are 4 of them, each on separate SSR's.

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  • \$\begingroup\$ What is the load you switch? How long are the wires? \$\endgroup\$
    – Andy aka
    Feb 27 '18 at 17:43
  • \$\begingroup\$ It's actually just a simple LED (it just accepts industrial voltage - 24V). I don't have a measurement on the wires handy but no more than 6-8 inches or so. \$\endgroup\$
    – brenzo
    Feb 27 '18 at 17:44
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    \$\begingroup\$ A link to the LED should be provided. \$\endgroup\$
    – Andy aka
    Feb 27 '18 at 17:46
  • \$\begingroup\$ A flyback diode would not hurt, and if you plan on plugging and unplugging a lot some ESD protection would be prudent. \$\endgroup\$
    – Trevor_G
    Feb 27 '18 at 17:50
  • \$\begingroup\$ I think you need to check if real inrush current for this industrial "piece of engineering" is under 500 mA. I am afraid it could be 2-3A short peak that kills the weak SSR. The "500mA" was probably on AC supply, but when you hit it hard with 24 V, who knows. \$\endgroup\$ Feb 27 '18 at 19:56
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What is the load you switch?

It's actually just a simple LED (it just accepts industrial voltage - 24V)

No it isn't.

It's an LED module that can run from AC or DC and has in all probability, a bridge rectifier and smoothing capacitor that has an inrush current. The data sheet states this: -

Maximum inrush current max. 500 mA

That is right at the limit of your TLP222A's capabilities and will seriously degrade the life of that product. Toshiba say this: -

Note: Using continuously under heavy loads (e.g. the application of high temperature/current/voltage and the significant change in temperature, etc.) may cause this product to decrease in the reliability significantly even if the operating conditions (i.e. operating temperature/current/voltage, etc.) are within the absolute maximum ratings.

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  • \$\begingroup\$ Thanks, I see the issue. Do I counteract this by using an SSR capable of providing 500mA under normal operating conditions? \$\endgroup\$
    – brenzo
    Feb 27 '18 at 18:10
  • \$\begingroup\$ It’s hard to think of a better alternative than a more beafier SSR. \$\endgroup\$
    – Andy aka
    Feb 27 '18 at 18:16
  • \$\begingroup\$ +1 That restrictions page is rather heavy huh. "PRODUCT IS NEITHER INTENDED NOR WARRANTED FOR USE IN EQUIPMENTS OR SYSTEMS THAT REQUIRE EXTRAORDINARILY HIGH LEVELS OF QUALITY AND/OR RELIABILITY," hmmm... define extraordinary please. \$\endgroup\$
    – Trevor_G
    Feb 27 '18 at 18:19
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    \$\begingroup\$ @Trevor_G - Heh. It's like the the old saying about price, "If you have to ask, you can't afford it." If you're worrying about whether a system requires an extraordinary level of reliability, you should assume that it does. Murphy's Law. Or maybe Finagle's. \$\endgroup\$ Feb 27 '18 at 19:06
  • \$\begingroup\$ Yup, you just have to wonder what lawsuit event made them decide to put that in big bold letters.. \$\endgroup\$
    – Trevor_G
    Feb 27 '18 at 19:17

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