Browse Prior Art Database

Power On/Off Sequencing of Dual Voltage Regulators

IP.com Disclosure Number: IPCOM000038905D
Original Publication Date: 1987-Mar-01
Included in the Prior Art Database: 2005-Feb-01
Document File: 2 page(s) / 44K

Publishing Venue

IBM

Related People

Langer, P: AUTHOR [+3]

Abstract

This article describes a circuit arrangement which provides a predefined power-up and -down sequence with power-up under external input control and power-down under microprocessor control. The circuit disclosed herein addresses the power-on/off sequencing of two voltage regulators used to provide conditioned power in a microprocessor-based controller module. Referring to the drawing the circuit has two voltage regulators, U1 and U2. A conditioned battery power input for U1 and U2 appears at the line labeled "+V12". Diode CRT4 is used to prevent component damage in the event the input line +V12 becomes negative. Zener diode CRT5 is used to clamp voltage transients greater than 28 volts in magnitude. Capacitor C9 helps to filter out supply line noise. The input labeled "-BATTGND" is the ground return line.

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Power On/Off Sequencing of Dual Voltage Regulators

This article describes a circuit arrangement which provides a predefined power- up and -down sequence with power-up under external input control and power- down under microprocessor control. The circuit disclosed herein addresses the power-on/off sequencing of two voltage regulators used to provide conditioned power in a microprocessor-based controller module. Referring to the drawing the circuit has two voltage regulators, U1 and U2. A conditioned battery power input for U1 and U2 appears at the line labeled "+V12". Diode CRT4 is used to prevent component damage in the event the input line +V12 becomes negative. Zener diode CRT5 is used to clamp voltage transients greater than 28 volts in magnitude. Capacitor C9 helps to filter out supply line noise. The input labeled "-BATTGND" is the ground return line. Regulator U1 is turned on only by the input control line labeled "-ON". When this line becomes logic 0, the base- emitter junction of transistor Q4 becomes forward biased causing Q4 to turn on. This causes capacitor C6 to charge through resistor R2. When the voltage at C6 and U1 input VIGN is positive. the regulator turns on. Once the regulator is on, it remains latched on independent of the VIGN input voltage until the microprocessor-controlled input +TOD becomes logic 0. At that point a controlled shut down occurs. By having the microprocessor-controlled regulator shutdown, volatile data can be saved and hous...