Any reason you're not considering a thermal inrush current limiter, such as
http://www.wecc.com/inrush.html

?  Just place it in series with the load, and you're off to the races.

-Adam

On 2/24/08, Forrest Christian <forrestc@imach.com> wrote:
> I am working on an application where the standard R/C timing
> forovercurrent protection in a device is not sufficient.... For those
> really interested we're talking about a L6206, driving a load where
> there is an internal capacitor.
>
> What happens is that the L6206's overcurrent protection kicks in during the initial capacitor inrush.  The amount/duration of the current is not
> sufficient to damage the L6206 (it's within the ratings), but it is enough to trigger the overcurrent for long enough that the device shuts
> down and the load never fully powers up.   I can tweak the R/C values and get it to power up, but then short circuits will occasionally kill
> the device, due to the short cycle.   And so on.
>
> My thought is to put an external circuit between the overcurrent detect output and the enable pin which allows me to more finely adjust what I
> want the overvoltage circuit to do.  The goal is to be able to delay the shutdown by around 5us or so (adjustable) and then keep it off for a few
> seconds.  I was thinking about the 8 pin pics - however, with a 500ns instruction time, this sure doesn't look reasonably likely to work for
> me - especially if I want to control both OCD output/input pairs.   I was also looking a bit at the AVR equivalent since it looks like the
> instruction time could be as low as 125ns, but still, I'm not sure that's fast enough.   There is also the possibility of using an external
> XTAL, but I'd like to avoid that.
>
> Because this is for a design which is fairly late in it's design cycle (somehow we didn't catch this until "beta"), I don't have a lot of space
> - and I'd like a small solution.   I was wondering if there was something else I missed...  I will be playing a bit with a 556-like
> circuit, but intuitively it feels that this would have similar issues to the R/C which won't work for me.
>
> -forrest
>
>
>
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