Electronics > Projects, Designs, and Technical Stuff
Exploding IC in buck converter
Siwastaja:
Alti, I usually detect sarcasm quite well but now I have to ask, are you serious or joking?
thm_w:
--- Quote from: Siwastaja on April 01, 2020, 12:41:47 pm ---For an even remotely robust system, you need to look the "working peak reverse voltage" spec, which is only 26V; it will likely conduct and leak excessively in a 24V automotive system when the engine is running, causing another set of problems (excessive heating, possibly only in some units, which may only become a problem after many hours of runtime...) . SMBJ30CA would be the lowest acceptable from that series, but then again, we are back to 48.4V max clamping voltage, way over the abs. max. rating of the IC. I think there is no way out by just replacing the TVS with another.
--- End quote ---
I agree that it is not an ideal design. But it looks like the maximum continuous automotive voltage tested in this certification is 28.2Vdc, does that sound right? Everything else is ms bursts.
http://www.emcprima.com/FileUPLoad/DownLoadFile/635792103688970689.PDF
http://read.pudn.com/downloads226/ebook/1062022/ISO16750-1.pdf
T3sl4co1l:
True enough, but I would add these two caveats:
1. Add your formal complaint that you disagree with the choice, for such-and-such reasons;
2. Record evidence of the decision process (conversations -- insist on e-mailed discussion; emails, design documents, datasheets, and approval by the boss guy).
A faulty converter for an aftermarket automotive gizmo doesn't seem to be a very serious concern, but this is well worth keeping in mind anywhere the stakes are higher.
Tim
mzzj:
--- Quote from: thm_w on April 02, 2020, 09:36:15 pm ---
--- Quote from: Siwastaja on April 01, 2020, 12:41:47 pm ---For an even remotely robust system, you need to look the "working peak reverse voltage" spec, which is only 26V; it will likely conduct and leak excessively in a 24V automotive system when the engine is running, causing another set of problems (excessive heating, possibly only in some units, which may only become a problem after many hours of runtime...) . SMBJ30CA would be the lowest acceptable from that series, but then again, we are back to 48.4V max clamping voltage, way over the abs. max. rating of the IC. I think there is no way out by just replacing the TVS with another.
--- End quote ---
I agree that it is not an ideal design. But it looks like the maximum continuous automotive voltage tested in this certification is 28.2Vdc, does that sound right? Everything else is ms bursts.
http://www.emcprima.com/FileUPLoad/DownLoadFile/635792103688970689.PDF
http://read.pudn.com/downloads226/ebook/1062022/ISO16750-1.pdf
--- End quote ---
Real-life is definitely worse than that. Maybe you misinterpreted the standard or its not very good stardard to go with at all.
On a cold day I remember measuring 15.8v from VW alternator. That would be 31.6v for 24v nominal system.
This is a graph from Bosch (Bosch Automotive Electrics and Automotive Electronics book)
I wouldn't design anything for below 32v.
magic:
--- Quote from: Siwastaja on April 02, 2020, 09:02:27 pm ---Alti, I usually detect sarcasm quite well but now I have to ask, are you serious or joking?
--- End quote ---
We are in a Poe's law singularity. True believers are so crazy and trolls are willing to go so far in their exploits that there no longer is any practical difference.
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