From: RussellMc <apptechnz@gmail.com>
To: Microcontroller discussion list - Public. <piclist@mit.edu>
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Date: Thu, 6 Feb 2020 01:27:12 -0800
Subject: Re: [EE] 78L05 (SO8) overshoot on removal of over-current event?
Thread-Topic: [EE] 78L05 (SO8) overshoot on removal of over-current event?
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On Thu, 6 Feb 2020 at 06:50, David Van Horn <
david.vanhorn@backcountryaccess.com> wrote:

> I've not seen this exactly, but I have seen a lot of problems with the L
> version being defective in various ways.  I generally wouldn't trust them=
..
>
> They (and actually most PNP based regulators) can be damaged by the input
> being shorted to ground, if the output capacitor is large.  This is not
> well documented, you might have to go back to Motorola data sheets from t=
he
> 1980's to find it documented, but the output stages are still much the
> same.   There are more modern parts that are immune.
>
> Normal method  to protect against this is to place a reverse biased diode
across the regulator so that the output capacitor will discharge via the
diode if the input is shorted.

Worst case a power off event may qualify if there is a heavy load on the
input side from loads.

I recall, but now not why in detail, that many decades ago we decided that
the 78Lxx regulators were not worth using compared to the 'full spec' ones.



       Russell
--=20
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