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LOW CURRENT REGULATOR WITH NO QUIESCENT CURRENT

IP.com Disclosure Number: IPCOM000005614D
Original Publication Date: 1986-Oct-01
Included in the Prior Art Database: 2001-Oct-19
Document File: 1 page(s) / 57K

Publishing Venue

Motorola

Related People

Dave Bush: AUTHOR

Abstract

Battery-powered microprocessor electronics often requires a regulated voltage (e.g., 5 vdc) under operating conditions, while only using a lower standby voltage (e.g., 3.5 vdc) to retain RAM data when not operating. If the microprocessor system is comprised of CMOS devices, the standby current drain need only be on the order of microamps or less for small systems. However, most commercial regulators require some quiescent current to perform the regulation, which creates an additional battery drain under standby conditions, The circuit shown below solves this problem by supplying regulated voltage to the system in the "ON" mode, while drawing no supply current to provide unregulated RAM voltage in the "STANDBY" mode.

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MOTOROLA Technical Developments Volume 6 October 1986

LOW CURRENT REGULATOR WITH NO QUIESCENT CURRENT

by Dave Bush

   Battery-powered microprocessor electronics often requires a regulated voltage (e.g., 5 vdc) under operating conditions, while only using a lower standby voltage (e.g., 3.5 vdc) to retain RAM data when not operating. If the microprocessor system is comprised of CMOS devices, the standby current drain need only be on the order of microamps or less for small systems. However, most commercial regulators require some quiescent current to perform the regulation, which creates an additional battery drain under standby conditions, The circuit shown below solves this problem by supplying regulated voltage to the system in the "ON" mode, while drawing no supply current to provide unregulated RAM voltage in the "STANDBY" mode.

   The figure illustrates that the CMOS switch, which is either a microprocessor output port or equivalent, controls the circuit by changing state when the system is shutdown to the "STANDBY" mode. In the "ON" mode, the switch provides current to the LM103 (4.3 vdc micro-power zener diode) and to the regulating bipolar tran- sistor. If the regulated output voltage is too low, the bipolar transistor is cut off, which allows the gate of the FET to rise toward the output voltage. This turns the FET on harder, allowing more current to flow to the system load. If the output voltage is too high, the bipolar transistor conducts to reduce the vo...