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Old 12th March 2010, 05:46 AM   #151
Vikt0r is offline Vikt0r  Ukraine
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Try

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Old 12th March 2010, 07:43 AM   #152
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Originally Posted by Vikt0r View Post
This is 1:1 similar to my experience. It's definitely not from nowhere. The fact itself wouldn't be that much a problem, if there would be any kind of protection circuit within the IC. But there's not, obviously.
You know the old say :" if you hear once is a rumour , if you hear for twice is a fact !"

I am also suspect a glitch or an transient spike from power source :
my PGA is on power stage with BD139/140 and zenner diode of15V and a lot of filtering (like 8600uF per side) and at the entering in transformer 230V I have a double filter with C and L on ferrite .
Never have such a problems like yours for almost now 3 years of daily usage .
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Old 12th March 2010, 08:56 AM   #153
Vikt0r is offline Vikt0r  Ukraine
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Originally Posted by didiet78 View Post
Viktor, picture would help. Maybe somehing wrong with analogue supply, LM3x7 have internal thermal protection. I thing you should measure 5v power supply. Just to make sure there is no over voltage in power supply.
Didiet
Didiet,
+5V is actually the digital supply, the analogue rails running at +/-15 volts.
And everything is fine with the analogue supply - it has a 1000 uF before the LM3x7 and 4700 uf after, also 2x470 uF in close proximity to the PGA 2310's leads.

Last edited by Vikt0r; 12th March 2010 at 09:06 AM.
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Old 12th March 2010, 09:05 AM   #154
Vikt0r is offline Vikt0r  Ukraine
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Quote:
Originally Posted by danzup View Post
You know the old say :" if you hear once is a rumour , if you hear for twice is a fact !"

I am also suspect a glitch or an transient spike from power source :
my PGA is on power stage with BD139/140 and zenner diode of15V and a lot of filtering (like 8600uF per side) and at the entering in transformer 230V I have a double filter with C and L on ferrite .
Never have such a problems like yours for almost now 3 years of daily usage .
Actually, I suspect the glitch coming from DIGITAL part's supply. A PGA is a software-driven digital pot. The analogue stage is powered from bipolar analogue supply, and when the mentioned run-away state occurs - the circuit draws the power from analogue rails, BUT the state itself caused by wrong behaviour of DIGITAL (control) part of the chip (I suspect). Did anyone see a PCM2702 (USB DAC) loosing sync when a fridge turns on in the kitchen?? So, I suspect something similar in our case - so it has nothing to do with the analogue supplies, even if this current burns the IC at the end.
I am going to try better filtering, maybe increase cap after the regulator, but not sure how to check if it helped. Not eager to wait until this happens again.

Linuxworks, don't you remember what supply did you use to power digital part of your projects?
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Old 12th March 2010, 09:10 AM   #155
Vikt0r is offline Vikt0r  Ukraine
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Originally Posted by danzup View Post
at the entering in transformer 230V I have a double filter with C and L on ferrite .
Will implement this. Anyhow, I would go back to the beginning and point to a fact, which has to be considered by designers, IMHO: such a run-away state IS possible, it CAN destroy the chip - would make sense to think about. Or, at least it can serve as a warning for further PGA23xx implementers.
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Old 12th March 2010, 09:11 AM   #156
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Victor, i think 4700uF after LM3x7 is too big, 100uf is enough.
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Old 12th March 2010, 09:18 AM   #157
Vikt0r is offline Vikt0r  Ukraine
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Originally Posted by didiet78 View Post
Victor, i think 4700uF after LM3x7 is too big, 100uf is enough.
Maybe it's too big, but 4700 would never be worse than 100 in terms of spike filtering... Again, see my post above - I don't think the problem's coming from analogue supply. I measured the voltage across the regulators when the chip was naturally burning - and it was rock solid (+/-14,2 V exatly, in my case), so the PS was up and okay. The digital voltage I measure is 4.98 V across the PGA's leads.
It is bypassed with a Sanyo OSCon close to the IC.
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Old 12th March 2010, 10:48 AM   #158
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Originally Posted by Vikt0r View Post
Oh, surely I will And do you have any IDEA about the subject, or you just enjoy jokin' about mine?
I am dead serious. But apparently my point isn't picked up.
That's OK.
Good luck with your project.

jd
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Old 12th March 2010, 12:13 PM   #159
Vikt0r is offline Vikt0r  Ukraine
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Quote:
Originally Posted by janneman View Post
I am dead serious.
Huh, scary!
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Originally Posted by janneman View Post
But apparently my point isn't picked up.
Apparently, I did not notice a point to pick up other than "I know the answer, but not telling you..." Sorry...aren't you, by an accident, work for TI? Or may it be you are so much worried about TI because it somehow affects the business of "LinearAudio.nl"? Because the only point that shines through your posts is that some stupid ones try to blame the mighty TI, while they are just not clever enough to make the thing properly (like others can ). I did ask you already - why you take this in such an offensive-resisting manner - but you didn't answer. At the other hand, you simply ignored some obvious observations coming not only from me, which alltogether exclude your "points" from the list of possible reasons.

Others have came up with ideas, suggestions, tried to participate in 2-way idea exchange. Just checked back your posts - and sorry to state, your "point" is a menthorship tone floating around lack of proper approach of poor implementers. And I have no intention to prove you that everything's fine with my (and others) design - and there IS a problem with a particular IC and it's stated NOWHERE in TI's documentation. Or maybe TI members have access to some secret erratas?
I'm enough self-aware to trust myself and argumented replies of community members. Hope others will do as well.

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Good luck with your project.
Thanks a lot, this seems to be the only useful idea coming from you.

Last edited by Vikt0r; 12th March 2010 at 12:36 PM.
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Old 12th March 2010, 12:29 PM   #160
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for my various PSUs, what I often did was to use a TLE rail splitter to take 24 or 10v and create a virtual ground. the TLE chip would also get hot IIRC, once runaway started to happen.

one of the diagrams I followed had a 10ohm R between digi gnd and analog gnd. I think I did install this and it worked for a while, using a 5v from my arduino and the analog voltage came from a 317 based supply that was virtual gnd split (nothing was true bipolar in my test setups).

another circuit did not share that 10ohm 'gnd breaker' idea. but all of my 3 pga builds have had this heatup stuff happen. things would work just fine for days and even weeks. I would exercise the pga chip quite a bit (lots of IR remote up down requests and even a lot of glide/ramps inside for-loops).

power was always on to those chips. I did swap inputs and that might have been significant. perhaps shorting some inputs (1/4" trs plug siding thru the shorting metal jack) would cause it go freak out somehow? I stopped using rca plugs and have gone to stereo TRS to carry my line levels. you can't use trs's without shorting as they are just that way when you insert or remove them. this is the only thing I can think of; and it still does not explain the freak-outs that happen all on their own (no jacks being changed).
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