7810 output voltage spiking?

[Rob]

No, strangely enough it does not run hot.. BTW, the setup they have is the
1044a (higher output A rating) in a voltage doubler configuration. a 12 volt
wallwart goes through a protection diode (then, it comes out about 11.5v).
This 11.5v gets sent to the 7810. The 7810 feeds the 10 volts to the 1044
voltage doubler, and the voltage doubler feeds its aprox 15v to a 7812
(which makes sense because the powersupply line voltage is 12 volts and for
real regulation you need more than the output voltage). Unlike I once
thought, the 1044 doubler is feeding *only* the 7812. The other 1044 (the
one that doesn't blow up) is being fed from the same 7810, and it is okay.

So, by this, I can say that the 7810 is *not* the culprit.

Now, I *am* looking at this 7812. I realize that this 7812 is capable of
sourcing far more current than the 1044 voltage doubler is capable of
handling, (I believe a 7812 can source 1000ma, whereas the doubler can only
source, oh, 150ma!) so, with this in mind, I will first change out the 7812,
then look for a short or near-short somewhere in the 7812 supply circuits if
it occurs again.

Thanks

Rob



----- Original Message -----
From: "danial stocks" <diode at hotmail.com>
To: <synth-diy at node12b53.a2000.nl>
Sent: Sunday, October 22, 2000 1:04 AM
Subject: Re: 7810 output voltage spiking?


>
> >Some 78xx regulators *do* output a higher voltage
> >when there is no output current. Maybe your
> >switched regulator doesn't draw current in the first
>
> I dont think this is the problem... most reg/smps chips do expect a little
> surging on the inputand so are at least a bit protected against this..
even
> if not, the surge if it is going to damage should do it pretty
immediately,
> not in 15 mins.. I'd be looking for something close to failure time.. Dont
> know of the actual setups for the LTC1044 chip, but if using inductor in
> system maybe consider that wrong inductance is causing excess current
> consumption - a too small val can cause a high idle current.. does the
chip
> run hot before failing?
> Cheers,
> Dan
> >
> >-----Ursprüngliche Nachricht-----
> >Von: Rob <cyborg_0 at iquest.net>
> >An: Synth-DIY list <synth-diy at node12b53.a2000.nl>
> >Gesendet: Samstag, 21. Oktober 2000 20:19
> >Betreff: 7810 output voltage spiking?
> >
> >
> >I have a problem.
> >
> >I have a power supply that has a 15 volt input supplying voltage to a
7810,
> >then, I take the 10v out from there and put it into an LTC1044A. But, for
> >some reason, after being on for about 15 minutes, the LTC1044A dies.
> >
> >BTW, the 1044 is a switching type regulator.
> >
> >Now, my question is, could the 7810 be allowing a spike on power-on to
get
> >past regulation and damage the LTC1044A? I would think it unlikely, but I
> >am
> >wondering if anyone has had such experiences with this sort of thing.
> >Changing the LTC1044a merely smokes another LTC1044a.
> >
> >I am seriously believing its this 7810, but, the 7810 does not seem to be
> >out of regulation, on the contrary is is holding a very solid 10 volts
> >exactly according to my recently cal'd scope.I have not been able to
> >capture
> >the power on spike either.
> >
> >What gives?
> >
> >Rob
> >
> >
> >
> >
>
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