Browse Prior Art Database

Power On/Off Sequence with Output Control for Multiple Power Source System

IP.com Disclosure Number: IPCOM000114849D
Original Publication Date: 1995-Feb-01
Included in the Prior Art Database: 2005-Mar-30
Document File: 4 page(s) / 78K

Publishing Venue

IBM

Related People

Nakazawa, Y: AUTHOR [+3]

Abstract

Disclosed is a method for controlling power-on/off sequence between a system unit and an expansion unit both of which are operating on the different power sources of each unit, using output control of the logic inside the system. An adequate power-on/of sequence control between the system unit and the expansion unit is necessary for preventing a latch-up of CMOS devices which can be caused by a high-level output toward the devices whose power is lower than its required level during power-on/off transitions.

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This is the abbreviated version, containing approximately 52% of the total text.

Power On/Off Sequence with Output Control for Multiple Power Source
System

      Disclosed is a method for controlling power-on/off sequence
between a system unit and an expansion unit both of which are
operating on the different power sources of each unit, using output
control of the logic inside the system.  An adequate power-on/of
sequence control between the system unit and the expansion unit is
necessary for preventing a latch-up of CMOS devices which can be
caused by a high-level output toward the devices whose power is lower
than its required level during power-on/off transitions.

      Fig. 1 shows a docking system into which the subject invention
is implemented.  System unit (SU, *1) and Expansion unit (EU, *2)
have their own power sources (*3, *4) that can be AC-to-DC Adapters
or Batteries.  SU and EU also have their own power modules (*5, *6)
that supply adequate level power (VCC)s to the logics (*8, *9), and
control to turn on/off the VCCs according to a common signal,
POWER-ON (*7).

      SU and EU are connected via bus I/F (*10), so that EU provides
SU with various I/O devices and adapter-card I/F in EU.  Power-on/off
sequence control is required between the logics of SU (*8) and EU
that operates on their own power sources which may have different
on/off timings.

      In SU logic, an input signal is provided in each LSIs (*11)
that tri-states all the output signals and neglects all the input
signals.  This input can be a signal already exist for another
purpose such as reset, test use, etc.  A control signal, HI-Z (*...