Triac Optocoupler Spec Sheet Question - Page 1
Forum section: electronics / projects

author: lilJohn
author_rank: Contributor
timestamp: September 04, 2024, 02:12:29 am
content: I have a number of questions concerning Triac Optocouplers. Example numbers will be pulled from a MOC3063M datasheet I am currently looking at (https://www.onsemi.com/pdf/datasheet/moc3163m-d.pdf).Are "Blocking Voltage" (p1,Features) and "Off–State Output Terminal Voltage" (p2,Absolute Maximum Ratings: Detector) the same thing? If so, is there any reason the datasheet would use the two terms interchangeably?Do the following isolation voltage specifications refer to between the detector and emitter side, the IC packaging, the internal thyristor, or something else (VPR, VIORM, and VIOTM)?Would exceeding the rated Off–State Output Terminal Voltage for a Triac Optocoupler, e.g. exceeding 600 V only damage the zero-crossing circuit that I presume to protect the circuit the Optocoupler connects to from voltage spikes? Or is that voltage similar to a MOS's rated Vds/ BJT's rated Vce(https://electronics.stackexchange.com/a/402772)? If only the former case,*Assuming that I don't need the function provided by the zero-crossing circuit, what is the maximum voltage I can switch on a MOC3063M? (Proper switching behavior using Pins1&2to control4&6excluding whatever is provided by the zero-crossing circuit)? My main issue is that while the spec sheet provides the device's Total Power Dissipation and I can probably find and assume some PDIP6 Junction-to-Ambient thermal resistance (ThetaJA) that I eventually find, I don't immediately see: a current-main terminals voltage behavior figure, specification that specifies such, or a thyristor spec that I can indirectly figure out the power dissipation as a function of current.Sorry that I am not an EE and thanks in advance!*edit, clarification: cutting the AC source is an appropriate way to turn off the thyristor; the gist of the question is asking whether or not if I put a voltage source >600 VAC, e.g. 1E-5 A @ 1.4k VAC (14 mW), will damage the device's ability to switch power with the optocoupler; the device is rated for 250 mW (page 2,ABSOLUTE MAXIMUM RATINGS: Total Device).

author: Phil1977
author_rank: Frequent Contributor
timestamp: September 04, 2024, 02:44:44 pm
content: Quote from: lilJohn on September 04, 2024, 02:12:29 amAs far as I understand: Yes. Probably "blocking voltage" was just a more catchy term for the general description.Quote from: lilJohn on September 04, 2024, 02:12:29 amBetween detector and emitter side.Quote from: lilJohn on September 04, 2024, 02:12:29 amIt´s rarely possible to say what happens if you exceed the absolute max ratings. As clearly written in the datasheet:"Stresses exceeding those listed in the Maximum Ratings table may damage the device. If any of these limits are exceeded, device functionality should not be assumed, damage may occur and reliability may be affected."Of course the current and energy of your source seems to be really low. Probably the TRIAC just gets conductive by the overvoltage, dissipates the few mW and survives. But no one can guarantee that.Can't you put a transient voltage suppressor (TVS)-diode parallel to the triac? Then the power would be dissipated in a part that´s designed for that task.PS: If the absolute max ratings allow a certain dissipation you can not assume that it doesn't matter where the power is dissipated. It´s easily possible that in case of an overvoltage breakdown an other part of the semiconductor is stressed than in normal operation.

author: lilJohn
author_rank: Contributor
timestamp: September 05, 2024, 07:25:53 am
content: Hey, thank you for answering my questions!Quote from: Phil1977 on September 04, 2024, 02:44:44 pmGood note -- such as the isolation between the detector and emitter.Quote from: Phil1977 on September 04, 2024, 02:44:44 pmThat's a good idea. Thank you for the suggestion! (I guess it really shows that my background isn't EE).