Browse Prior Art Database

Parallel Channel Electrostatic Discharge Suppressor

IP.com Disclosure Number: IPCOM000114792D
Original Publication Date: 1995-Feb-01
Included in the Prior Art Database: 2005-Mar-29
Document File: 4 page(s) / 170K

Publishing Venue

IBM

Related People

Calabrese, GM: AUTHOR [+2]

Abstract

Disclosed is an Electrostatic Discharge (ESD) suppressor for IBM*'s OEMI mainframe parallel channels that is optimally located between the tailgate external cable connector and the channel board so as to address all ESD problems related to the external Bus and Tag I/O cables thereby improving the ESD immunity of the parallel channels and offering the potential for cost reductions to the board and channel driver circuits through the reduction of ESD immunity required for these circuits. A commercially available voltage activated switching material is packaged so as to be completely retrofitable without modifications to the channel board or tailgate connector while meeting all functional requirements of the OEMI parallel channels.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 34% of the total text.

Parallel Channel Electrostatic Discharge Suppressor

      Disclosed is an Electrostatic Discharge (ESD) suppressor for
IBM*'s OEMI mainframe parallel channels that is optimally located
between the tailgate external cable connector and the channel board
so as to address all ESD problems related to the external Bus and Tag
I/O cables thereby improving the ESD immunity of the parallel
channels and offering the potential for cost reductions to the board
and channel driver circuits through the reduction of ESD immunity
required for these circuits.  A commercially available voltage
activated switching material is packaged so as to be completely
retrofitable without modifications to the channel board or tailgate
connector while meeting all functional requirements of the OEMI
parallel channels.

      ESD events have been a concern with Input/Output circuitry of
parallel channels for mainframes and associated device equipment.
Charges may build up on external bus and tag cables in the order of
1000 to 2500 volts simply through handling of the cables prior to
plugging to the channel tailgate.  Discharge of this energy through
the cables into the internal channel circuitry (i.e., channel
receiver/driver modules) can cause damage to sensitive components,
which then necessitates replacement of damaged units (i.e., channel
cards).  Unfortunately, many times these ESD damage events occur
during installation of the system in the customer's facility, causing
IBM to miss its scheduled install time.  ESD damage can also occur at
IBM when cables are plugged for system test, causing lost time and
replacement of expensive channel cards.

      ESD through said I/O cables may also occur with the cables
plugged to the tailgate when the other end of the cable is handled to
reconfigure the channel.  A person handling the cables may deliver a
15,000 volt charge to the channel simply by touching a serpent
contact of the external cable with a tool or finger.  People
typically carry this level of charge on their body in low humidity
environments common indoors in wintertime.  This discharged energy is
also sufficient to cause damage to internal channel circuitry.  This
event may also occur in the field and affect customer utilization of
the system.

      A related and more recent addition to the family of channel ESD
problems is termed the "neighboring channel problem", and may arise
when some channels are taken down for maintenance or upgrade, but
neighboring channels remain active.  In this situation, an ESD event
on a down line can induce a voltage pulse on a neighboring active
line through electromagnetic coupling of the lines via the channel
board circuitry where these lines run closely together.  The induced
voltage pulse may cause a "check stop" on the active channel thus
defeating the purpose of concurrent maintenance or upgrade activities
with the channels.

      The parallel channel ESD suppressor offers electrostatic
discharge...