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Simple Regulator for Low Voltage, Low Power Loss Applications

IP.com Disclosure Number: IPCOM000109206D
Original Publication Date: 1992-Aug-01
Included in the Prior Art Database: 2005-Mar-23
Document File: 2 page(s) / 87K

Publishing Venue

IBM

Related People

Meyer, J: AUTHOR

Abstract

This article describes the design of a simple voltage regulator circuit. The design is ideal for applications that require an unusual supply voltage to be derived from a standard supply. For example, consider a product that requires +5 volts for TTL logic and +3 volts for analog circuits. The product is powered from a standard +5 volt supply and uses the regulator to provide +3 volts for the analog circuits.

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Simple Regulator for Low Voltage, Low Power Loss Applications

       This article describes the design of a simple voltage
regulator circuit.  The design is ideal for applications that require
an unusual supply voltage to be derived from a standard supply.  For
example, consider a product that requires +5 volts for TTL logic and
+3 volts for analog circuits.  The product is powered from a standard
+5 volt supply and uses the regulator to provide +3 volts for the
analog circuits.

      The regulator circuit is based on a transistor switch operated
by a level compare circuit.  If the load voltage is lower than the
desired reference, the transistor is turned on.  Once the load
voltage exceeds the reference value, the transistor is turned off.

      Referring to the figure, the source of power MOSFET transistor
Q1 is tied to the regulator input voltage (VIN). The drain of Q1 is
tied to the load (VLOAD), allowing the transistor to switch power to
the load.  The gate of the switch is controlled by an operational
amplifier (op-amp U2), which compares VREF to VLOAD.  VREF is the
reference voltage provided in this case by U1, a digital-to-analog
converter (DAC).  Implementation of the reference voltage may vary.
If the DAC is used, refer to the manufacturer's data sheet or
applications notes for exact wiring details.  Finally, a filter
network of C1, C2, and R3 are connected to VLOAD.  R3 is required as
a load resistor to drain the capacitors when no load is c...