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Multiple Power Supply System without Complimentary Metal Oxide Semiconductor Large Scale Integrated Latch-Up

IP.com Disclosure Number: IPCOM000116451D
Original Publication Date: 1995-Sep-01
Included in the Prior Art Database: 2005-Mar-30
Document File: 2 page(s) / 50K

Publishing Venue

IBM

Related People

Narita, I: AUTHOR

Abstract

Disclosed is a multiple power supply system in which the voltage of each power supply output rises with the same voltage at power on. When a notebook Personal Computer (PC) is attached to an expansion unit like "docking station", normally, each DC/DC converter in the notebook PC and the expansion unit supplies 5 V to each logic circuit. Lately, Complementary Metal Oxide Semiconductor (CMOS) technology is used for the Large Scale Integrated (LSI) circuits. Latch-up failure mechanism is well known for CMOS LSI. It occurs when the input pin voltage of the LSI is above the LSI's Vcc voltage. In multiple power supply system, this situation may be occurred, especially, at powering on the system since one DC/DC converter may output its output voltage before the others.

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Multiple Power Supply System without Complimentary Metal Oxide Semiconductor
Large Scale Integrated Latch-Up

      Disclosed is a multiple power supply system in which the
voltage of each power supply output rises with the same voltage at
power on.  When a notebook Personal Computer (PC) is attached to an
expansion unit like "docking station", normally, each DC/DC converter
in the notebook PC and the expansion unit supplies 5 V to each logic
circuit.  Lately, Complementary Metal Oxide Semiconductor (CMOS)
technology is used for the Large Scale Integrated (LSI) circuits.
Latch-up failure mechanism is well known for CMOS LSI.  It occurs
when the input pin voltage of the LSI is above the LSI's Vcc voltage.
In multiple power supply system, this situation may be occurred,
especially, at powering on the system since one DC/DC converter may
output its output voltage before the others.  To prevent this
phenomenon, each DC/DC converter should output the same voltage
output at power on.  According to this invention, the reference
voltage to the respective DC/DC converters are controlled so that all
DC/DC converters output the same voltage at the power on.

      Fig. 1 shows the circuit of the invention.  Assume 5V DC/DC
converters in the notebook PC and the expansion unit.  In the Figure,
"LOW VOL SELECTOR" selects the lower voltage from the input voltages.
The relation between Vref' and Vref1 or Vref2 at the power on is in
Fig. 2.  Vref' gradually rises and is input...