Re: 4420 driver ICs

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: Jan Wagner <jwagner-at-cc.hut.fi> 


On Thu, 1 Apr 2004, Tesla list wrote:
 > Original poster: Fucian-at-aol-dot-com
 > In a message dated 4/1/2004 10:30:38 AM Eastern Standard Time,
 > tesla-at-pupman-dot-com writes:
 >
 >  > Have you added the proper capacitors between ground and Vcc/Vdd right
 >  > next to the chip? 1 electrolytic + some ceramics or plastic caps?
 >  > Depending on your board layout, leaving out those local RF decoupling 
caps
 >  > on the supply rails can lead to really nasty spikes on the
 >  > chip when it
 >  > 'runs', could be high enough to zap them
 >
 > Hmmmmmmmmmmmm.....Well i have it powered by a regulator...Does it still
 > need the caps?

Definitely. A minimum are the small ceramic caps on the regulator input
and output, required mostly if you use 780x series which may get unstable
without the caps. 10nF is ok for those.
Or check the datasheet. www.google-dot-com "lm7812 pdf" (and replace 'lm7812'
with your regulator part nr)

Next to the driver chip, a 1uF electrolytic or tantal, and 100nF ceramic
or plastic pulse cap. Values aren't critical, you can also use 47uF
220nF, or what you find in your parts box.

Hope these fix the frying problem!
cheers,
  - Jan

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