Re: [SI-LIST] : Request for help

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From: Michael Nudelman (mnudelman@tellium.com)
Date: Wed Oct 25 2000 - 15:04:21 PDT


Yaserh:

Seems like you have a de-coupling problem. If you can assure me, that
your device is powered exactly like this: 110V(220V)Transformer -
rectifier - capacitor, and you do not connect this device to any other
devices (all connections are within the device), thatn I can almost
certainly tell, that you do not have good de-coupling capacitors.

Advice: calculate your current and use 1) switching grade electrolitic
capacitors and 2) 0.1uF capacitors per every chip with one VCC/GND pin
pair on the board or per every VCC pin of every device on the board.
If it is a short brownout - this will help.

Mike.

yaserh wrote:

> Dear Sir : I have a problem in a microcontroller board works with a
> linear power supply from a power transformer.The problem is when any
> device is in the AC plug with my board switches on or off my board
> hangs.I have checked my +5V supply with the Digital storage
> oscilliscope and i find in switching the other devices i found spike
> of level +6V for duration of 100 ns over the +5V and in other times
> it's -6V for duration of 100 ns down the +5V. I have reviewed my PCB
> i found no problem. I put a line filter with my AC line it does not
> solve the problem. I need to know from where this spikes come to my
> circuit and how i can solve this problem. Waiting for replyWith my
> best regardsYasser El-haddad

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