Optocoupler datasheets

bitrex · 2024-05-29T15:15:17+00:00

Optocoupler datasheets seem like kind of a mess, I try not to use them too often in situations where there's any kind of power budget because other than "shove some relatively huge current through the LED like 5-10 mA" it's hard to know what you can get away with.A light load on the transistor side will definitely reduce the forward current required (and of course slow the speed to a crawl) but who can say by how much while still ensuring the thing will turn on sufficiently to saturate the output?The CTR varies widely from process variation, varies with temperature, varies with collector emitter voltage, varies with forward current, and the data sheets are full of caveats like "At I_f < 1 mA, note CTR variation may increase" and "Graphs are representative, not indicative of actual performance." ????Any suggestions for how to approach methodically/mathematically selecting drive current would be appreciated, thank you! ("Don't bother" a valid option)

May 29, 2024 Last reply: 2 years ago 21 Replies

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Edward Rawde 2 years ago

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Have you used anything like these?

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What other methods are available which can cope with communication between equipment on different power line phases? Apart from the obvious transformer isolation used in computer networking? And RF isolation such as Wireless networking and Bluetooth.

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john larkin 2 years ago

We use isolated ADCs (like ADUM7703) and logic isolators (like the ADUM1400 series.) Some newer ADCs and isolators include the isolated dc/dc converter to power the high side, which is very cool.

There are some cheap electrical-metering multichannel ADCs that include the power isolation.

There are also isolated mosfet gate drivers.

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