Browse Prior Art Database

On-SIMM Resistance Terminators for Solving Ground Bounce Noise on Control Lines

IP.com Disclosure Number: IPCOM000118794D
Original Publication Date: 1997-Jul-01
Included in the Prior Art Database: 2005-Apr-01
Document File: 4 page(s) / 95K

Publishing Venue

IBM

Related People

Tran, KD: AUTHOR

Abstract

Disclosed is a method which adds On-SIMM Resistance Terminators for cleaning up the Ground Bounce noise on control lines at DRAM devices on the 72-pin industry standard Single In-line Memory Module (SIMM).

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

On-SIMM Resistance Terminators for Solving Ground Bounce Noise on
Control Lines

      Disclosed is a method which adds On-SIMM Resistance Terminators
for cleaning up the Ground Bounce noise on control lines at DRAM
devices on the 72-pin industry standard Single In-line Memory Module
(SIMM).

      The Row Address Select (RAS) control signals will be used as a
sample for discussion of this disclosure.  The 72-pin industry
standard SIMM provides up to four RAS lines, and each RAS line is
directly connected to multiple DRAMs without on-SIMM termination.
The glitches  are seen on all of the RAS lines at any DRAM(s) on the
SIMM, as shown in  Fig. 1, caused by the Ground Bounce noise.  When
the numbers (N) of memory data outputs are simultaneously switched
from "high" to "low" from  DRAMs into (N) corresponding capacitive
loads, an (N) larger transient  current flows through the SIMM ground
lane to discharge (N) capacitance  loads.  As a result of ground
inductance, this current produces an (N)  larger noise voltage pulse
at the ground terminals of DRAMs on the SIMM.  This ground noise,
known as ground shifting, occurs in the internal ground reference
voltage due to output switching, called Ground  Bounce.  The
magnitude of the ground noise, Vgnd, is equal to
          Vgnd = Lgnd(dI/dt)
  o  dI  -  Delta discharge current flows around the ground loop
             between the output pins of DRAM and the SIMM ground
             plane
  o  Lgnd  -  Inductance of SIMM ground system and DRAM package

      The internal ground of DRAM carries the Vgnd noise pulse, and
the input voltage is seen by the input circuit of DRAM, like the RAS#
control input, is equal to
          Input circuit sees:  Vin - Vgnd

      Therefore, the magnitude of glitches on the RAS lines varies
from several hundred milli-volts up to 1.8V when all outputs of DRAMs
switching...