From: [email protected]
Date: Sun Apr 22 2001 - 23:42:21 PDT
Hello Massimo,
Ground splitting is often used in mixed D/A boards to isolate "quiet"
analog ground from "dirty" digital ground. If you want to stay away
from problems due to digital spikes coupled to analog circuitry, use
two ground planes. Pay attention to large current spikes, if your LCD
drains lots of current.
I also recommend you to place a big capacitor in parallel with a small
selected one at the output of the power supply. If you want a better
noise rejection, use also a pi filter. ( C-L-C ). Place also good
capacitors between the supply pins of your Video Accelerator and the
right ground plane.
Diego Koch
STMicroelectronics
Agrate, ITALY
Email: [email protected]
______________________________ Reply Separator _________________________________
Subject: [SI-LIST] : Power Supply decoupling for Video Accelerator
Author: massimo.polignano ([email protected]) at internet
Date: 4/20/01 2:46 PM
Hallo everybody!
We are going to use a Video Accelerator (69000 Chips HiQVideo) to drive a
LCD. In the data book the manufacturer seems to be very much concerned with
PCB layout and power supply decoupling. They suggest the use of three
different grounds and power supply filtering using more than one LC or RC
cell and more than one decoupling capacitor of the same value in parallel.
Usually I prefer to have just one very good ground plane and one high
capacitance capacitor at the entrance of the power supply into the board
and one well selected capacitor (parasitic inductance, charge, ...) close
to the chip pins. Facing suggestions like those above, one is always in
doubt whether the chip designer made accurate tests, simulations and
prototyping or he just wants to stay on the safe side.
Does anybody out of there have any thought on the matter?
Thanks
m.p.
-------------------------------------------------------------
ESAOTE S.p.A. Massimo Polignano
Research & Product Development Design Quality Control Mngr
Via di Caciolle,15 tel:+39.055.4229402
I- 50127 Florence fax:+39.055.4223305
e-mail: [email protected]
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