Re: Voltage regulator instability


suputnic wrote:
John Popelish wrote:

suputnic wrote:
John Popelish wrote:

Yes. It also means that any linear 3.3 volt regulator has an awful
lot of voltage to burn up and will produce a lot of heat doing it.

It is only drawing a 20mA current steady state, so I thought heat would
not be a problem.

At 20 mA, it should work. What is the current drawn during the start
up transient, and how long does the transient last?

Sorry been away setting up and testing these things. The transient
current is 500 - 600 mA and it lasts about a second.

I wouldn't consider something that lasts a second being a transient.
Granted, you don't have a current probe to make an accurate
measurement, but a second is forever in the land of electromigration.


Hard to tell with
a multimeter. Two of my 3.3V regultors are measuring 2.7V, have they
been damaged by being added to a 12V adapter with no caps you reckon?
Or could they be originally faulty? The caps have made all the
differemce BTW, the heater killer adapter now is stable.


(snip)
The lack of regulated adapter is not the problem. An unstable
regulator combined with about 10 volts drop is the problem. You
should look for a 5 or 6 volt adapter for your next attempt.

I don't have any adapters of that size. Besides the spec sheet says the
regulator handles up to 30 or so Volts.

That means the voltage will not instantly destroy anything, but you
still have to make sure the temperature does not reach a destructive
level. If you can put your knuckle against the side of the regulator
while it is operating, it is doing fine, from a thermal standpoint.
If it makes you jump, not so much.

Temperature is fine.

.

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