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From: "Douglas J Petican"
Subject: Ground Bounce (SSN)
Date: Wed, 30 Oct 2002 13:08:23 -0500
Organization: Mountain Cablevision
NNTP-Posting-Date: Wed, 30 Oct 2002 18:07:54 +0000 (UTC)
X-Newsreader: Microsoft Outlook Express 6.00.2600.0000
I'm using a 74ALS541 and 74ALS573A together to implement a bidirectional
databus. The 573 latches the output data (LE=0) when the 541 is used to
read input. The 541 is tristated (CS=1) when data is being written to the
573. To read data I set LE=0 and CS=0. To write data I set CS=1 and LE=1.
The circuit works great except that on the ZH transition of the 541 with
greater than 3 high outputs creates ground bounce which causes the LE on
the 573 to temporarily go from low to high. My power supply voltage is 5V
and I'm using a 3M style prototyping board. I have power and ground running
along both top and bottom
I already have a 10uF tantalum cap in paralell with a 1uF cap from Vcc to
Vss. Are these good values? What about a 2-3pF between Vss pins and the
ground rail? The caps on the Vcc pins run from the pin to ground on the
top rail while the Vss pins connect to ground on the bottom rail. Is this
correct or should I connect the 10uF/1uF filter caps across the chip from
Vcc pins to Vss pins? I'm also considering switching to CMOS and using a
12V power supply to increase the noise margin.
Any other comments or suggestions would be greatly appreciated.
Thanks, Doug Petican
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