Hi all, I'm trying to identify a Motorola surface mount diode.
The code on the didoe is 607 with a datecode of 9318. It's a Motorola from the logo. I've not had success with google trying to find it, would anyone have any ides? I think it's azener, or perhaps a schottky.
Thanks Greg (sorry if this posts a second time, tpg doesn't seem to post out)
I can find a Motorola reference referring to their 1N607 and 1N607a diodes, which the reference states can be replaced with a 1N4001 - far from a Zener! Whether the "607" on your device refers to 1N607 or something entirely different though, is anyone's guess.
The reference sheet's here; click the thumbnail to download the PDF -
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You might want to contact WES in Ashfield (Sydney) and ask for their thoughts; though I haven't dealt with them in several years, I remember their staff being very knowledgable.
I didn't reverse engineer enough of the circuit and found this diode directly across a filter cap after a 2 diode rectifier in a smps after it heated enough to melt the solder on the board. (wound the external supply up to 15V with 100-150mA current limit set).
So the diode now measures around 0.7V forward and breaks down at around
17-18v.
In the circuit it's directly across the filter cap with no current limit resistor so I've either damaged a 15v zener or I've damaged a 15v schottky that was there for some unknon reason.
I've checked all the smd code websites and pdf that I can find but no reference to a motorola diode with code 607.
I'd suspect a 15V zener but I'm loathed to put one in there with no resistor. The smps circuit maintains it's fault without the diode, so I can still do some fault finding.
Hi, no it's not a 1N400x type didoe, it wouldn't have broken down at around 15v. See my reply to Phil, I expect it's a 15v Zener. Also, looks like the 1N607 is a DO-4 case style, not an SMA or SMC surface mount type case.
Sounds like maybe a zener, while regular diodes can drop as much as 1.1V at max rated current, 0.7V is regarded as "nominal". In actual fact; a DMM diode check is likely to show nearer 0.65V (even lower for fast diodes) - the diode check will actually show 0.7V on a zener.
Shottky-barrier diodes vary considerably depending on current rating, I've measured as low as 0.1V for big stud mounted rectifiers, and (I think) about
0.4V for the likes of a 1N5817 etc.
The low reverse breakdown adds credibility to the idea of it being a zener.
Phil is probably right with "crude crow-bar" - the not so cheap & nasty version uses a zener (taking Vgate into account) to latch a SCR across the rail, a fuse is pretty much essential.
Hi, the 15V breakdown also made me consider the schottky, that's a typical schottky breakdown voltage. But a zener sounds more logical than a schottky. However such a brute force approach is likley to cause collateral daamge within the smps than something more elegant.
BTW: you're unlikey to find many SB diodes less than 20V, except in VHF/UHF small signal applications.
They do however get used as sacrificial crowbars - I've found them occasionally protecting the G-S of the SMPS MOSFET in PC monitors - more often than not regulation failure caused core saturation and blew the internal structure of the MOSFET and/or the source current sense resistor, if the clamp diode protected anything at all - it was usually the SMPSU chip.
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