Re: Power-On Reset

From: Rich Grise (richgrise_at_example.net)
Date: 02/22/05 

Date: Tue, 22 Feb 2005 19:35:04 GMT

On Tue, 22 Feb 2005 15:20:51 +0000, Michael A. Terrell wrote:
> Rich Grise wrote:
>> On Tue, 22 Feb 2005 04:10:28 +0000, Paul Rako wrote:
...
>> > over a range of temperatures and loads. This is really a
>> > design challenge so don't take it lightly.
>>
>> What's wrong with a 1 uF cap from the POR pin to ground, with,
>> say, a 10K pullup?
>>
>> Thanks,
>> Rich
>
> If you ever had to troubleshoot equipment built that way you would
> never ask that question. The VTR interfaces for a video editing system
> at WACX in Orlando was designed for a reset generator chip, then they
> left out the chip and used a crappy R/C reset. The equipment worked
> when it was new but a couple years later it would only reset one out of
> 20 or more attempts. You could play around with the R/C values and make
> it work for a couple weeks, but they finally agreed to let me mod the
> equipment by stuffing the missing parts on the board and eliminated the
> problems.

But notice the operative phrase here - "designed for a reset generator
chip". That particular chip does, in fact, need a proper reset, as has
been covered in other posts in the thread.

I was talking about the kinds of chips that they made in the '80s, where
there was a pin specifically designed to take a cap and R, and has a
Schmitt trigger, and the whole chip is designed to get reset by that
little circuit.

But, as I've said in another post, I'm slowly being dragged, kicking and
screaming, into the 21st century. ;-)

Speaking of which, there was a family of "reset generator" chips once -
did they fade away too?

Thanks!
Rich

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