Electronics > Projects, Designs, and Technical Stuff
passing signals over galvanic isolation without an opto coupler
Marco:
Only problem with these digital isolators is the time quantization, but for khz range PWM I don't think the 325 ps jitter for Silabs matters.
mikerj:
--- Quote from: Simon on October 17, 2019, 09:26:13 am ---that is a different datasheet from the one i got off RS. Overall looking at opto couplers I have not found any that really shine at high temperature with specifications being vague or missing. Basically I think we need something else. Opto's are good but things have moved on and so have the demands of industry.
--- End quote ---
The datasheet on RS relates to slightly different part number (CNY17., CNY17G vs CNY17)
That a pretty vague statement, what demands do they not meet? If it's something concrete like reliability then seeking a better solution with the trade-off of increased complexity and/or expense is perfectly justified, but it sounds like you want to try something else out of interest.
Simon:
--- Quote from: Marco on October 17, 2019, 09:39:01 am ---Only problem with these digital isolators is the time quantization, but for khz range PWM I don't think the 325 ps jitter for Silabs matters.
--- End quote ---
I think we can just about call that of no significant influence, worse case is with PCM where ns is as small as i would be concerned about and with PWM I'm only worrying about µs at a few hundred Hz
Simon:
--- Quote from: mikerj on October 17, 2019, 09:53:15 am ---
--- Quote from: Simon on October 17, 2019, 09:26:13 am ---that is a different datasheet from the one i got off RS. Overall looking at opto couplers I have not found any that really shine at high temperature with specifications being vague or missing. Basically I think we need something else. Opto's are good but things have moved on and so have the demands of industry.
--- End quote ---
The datasheet on RS relates to slightly different part number (CNY17., CNY17G vs CNY17)
That a pretty vague statement, what demands do they not meet? If it's something concrete like reliability then seeking a better solution with the trade-off of increased complexity and/or expense is perfectly justified, but it sounds like you want to try something else out of interest.
--- End quote ---
Not out of interest. I am not comfortable with opto's after a few failures and looking at opto couplers as a whole (I went through a few Datasheets) I would prefer not to use them. The leakage over 80C changes from 2nA to 200nA. They are ideal to cheaply solve some problems but I do not feel comfortable with them in the application I am involved with and with every other part rated to 125C the opto's are now the weakest link.
floobydust:
Optocouplers aren't good with age or temperature, almost none of them are AEQ.
IC's using digital isolation with tiny air-core transformers are sexy but a challenge for EMC. Their high carrier frequency is not mitigated in any app notes or datasheets, as far as AD iCouplers. It's a great place to get bit in EMC testing with them.
For a single analog, using a transformer and PWM works for lowest cost. It depends on your isolation voltage, regulatory requirements and accuracy.
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