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Message

Re: Power Supply Sequencing - Latchup

2004-07-14 by tsvetanusunov

Hello Group,

I'm sorry I don't read all messages in this group and didn't saw that 
here are questions for me. Thank to Martin Koenig who e-mailed me 
directly and point this thread to me.

What we have so far is the following statistics:
In the first 500 pcs assembled boards we had with LPC2106 they were 
with 10/10 uf tant power supply capacitors and around 10% were with 
the problem of start-up. The problem was that if you plug and unplug 
the power supply to the board sometimes the code in LPC2106 is 
running and sometimes is not running, but oscillator is working in 
each cases, this happens no matter how long we hold reset low.
After the post in this group and the valuable comments from Bill 
Knight we changed the 3.3V capacitor to 47uF which decreased the 
boards with problems to only few.
Now with over 1700 boards assembled and tested I check today in our 
QC dept and they have only 6 boards with this problem left, which is 
too small quantity to worry about and to investigate (say to spend 
money on it from manufacturing point of view). 
I can send boards with such problem to Philips to investigate, in 
matter of fact Robert (philips_apps@yahoo) e-mailed me with such 
request after my first post. The problem is that this e-mail 
(tusunov@...) is used only to post on yahoo groups and I don't 
read it frequently. I read the message about one or two months later 
and reply to Robert asking for address where to send boards with this 
problem but never got reply (I suppose he doesn't read his Yahoo e-
mail often too :)))

Best regards
Tsvetan

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