Author Topic: Optocoupler LED Lifespan vs Current  (Read 490 times)

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Offline PentoadTopic starter

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Optocoupler LED Lifespan vs Current
« on: May 21, 2020, 08:07:39 pm »
I am using an EL357N optoisolator in a project and I am supplying it 5v through a 500 ohm resistor. It draws 7 milliamps. The absolute maximum rating for it is 50 milliamps. Do you think I am overdriving it and would it be better to lower the current? I understand this could affect the CTR but the output phototransistor is only driving the gate of a small mosfet at frequencies well below 1 hertz.
 

Offline thm_w

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Re: Optocoupler LED Lifespan vs Current
« Reply #1 on: May 21, 2020, 09:11:49 pm »
8mA is fine.
The absolute maximum rating is 50mA, and the "typical" rating is 20mA, which it should last many years on.

Keep in mind the spec and forward voltage change at various temperatures, CTR range, etc. But in your case 8mA has tons of headroom.

http://www.everlight.com/file/ProductFile/EL357N-G.pdf
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