Post 9uL7doiJOwY8rhvBAW by uint8_t@chaos.social
 (DIR) More posts by uint8_t@chaos.social
 (DIR) Post #9uL7dmfkzTJkXCi6uO by uint8_t@chaos.social
       2020-04-22T13:44:26Z
       
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       I'm getting extremely confused about RC snubber design for this particular board... I got to the point where nothing seems to make sense?I'm getting about 10x more parasitic capacitance than what I'd expect, and I'm starting to suspect I might have ESD damaged the MOSFET(s)
       
 (DIR) Post #9uL7dmuI7QwZGHViYy by uint8_t@chaos.social
       2020-04-22T13:45:44Z
       
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       Or is it my board layout? there is a little bit of overlap between SW and GND pours (on different layers of course)But I'd be surprised if this would cause hundreds of pF SW-GND capacitance.
       
 (DIR) Post #9uL7dnHgiReuQqSP20 by uint8_t@chaos.social
       2020-04-22T13:52:58Z
       
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       there is also this random mystery ringing I don't understand at all. it only comes at certain switch pulses, and only with no load.I suspect cross conduction but that means the driver IC is doing something very strange...
       
 (DIR) Post #9uL7dnU5yJaF3KGJN2 by uint8_t@chaos.social
       2020-04-22T13:55:59Z
       
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       I'm going to replace the LM5116 controller ICthat pulse is shorter than the minimum on time...
       
 (DIR) Post #9uL7dnf5JSNFbPP5V2 by uint8_t@chaos.social
       2020-04-22T16:47:25Z
       
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       high side gate drive looks actually good... I need to get a HV differential probe with 100+ MHz BW
       
 (DIR) Post #9uL7dnya8xyCZsWetE by uint8_t@chaos.social
       2020-04-23T15:31:43Z
       
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       the saga continues.I replaced everything, and it is still weird. It is ringing an awful lot, and I start to think it's my measurement setup... despite pigtail and shit.next I'll try to add a resistor to the HS gate drive as I'm afraid it turns on too fast, causing oscillation between Cgs and Cboot
       
 (DIR) Post #9uL7doBhMCShEYf8Km by uint8_t@chaos.social
       2020-04-23T15:33:24Z
       
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       I should do a writeup when I finally solve this puzzle and elaborate on how to debug dcdc converters in general. $search_engine does not provide adequate answers at the moment; apparently power electronics is a niche.
       
 (DIR) Post #9uL7doMghLFhmdnuSm by Zuph@octodon.social
       2020-04-23T15:41:27Z
       
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       @uint8_t Niche or deep and arcane blend of art, science, and possibly witchcraft? 😜
       
 (DIR) Post #9uL7doiJOwY8rhvBAW by uint8_t@chaos.social
       2020-04-23T15:44:18Z
       
       1 likes, 0 repeats
       
       @Zuph no, no. what you describe is RF engineering.