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VOLTAGE REGULATOR WITH ENHANCED PSRR PERFORMANCE

IP.com Disclosure Number: IPCOM000007518D
Publication Date: 2002-Apr-02
Document File: 5 page(s) / 88K

Publishing Venue

The IP.com Prior Art Database

Abstract

High power supply rejection ratios (PSRR) is one of the most important performance features of voltage regulators. Prior art voltage regulators obtained high PSRR using a two stage regulator comprised of a high PSRR band-gap (BG) reference and a high PSRR Output stage such as those of common art employing cascoded stages or high gain feedback loops. As a result, prior art voltage regulators suffered from overly complicated design that are difficult and costly to manufacture. The new voltage regulator is based on a new BG cell, which has line regulation "opposite" to the line regulation of the output stage which provides a BG block which has slightly decreasing output voltage with increasing input voltage. This novelty results in improved regulation and improved PSRR.

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VOLTAGE REGULATOR WITH ENHANCED PSRR PERFORMANCE

High power supply rejection ratios (PSRR) is one of the most important performance features of voltage regulators.   Prior art voltage regulators obtained high PSRR using a two stage regulator comprised of a high PSRR  band-gap (BG) reference and a high PSRR Output stage such as those of common art employing cascoded stages or high gain feedback loops.  As a result, prior art voltage regulators suffered from overly complicated design that are difficult and costly to manufacture.

                     The new voltage regulator is based on a new BG cell, which has line regulation “opposite” to the line regulation of the output stage which provides a BG block which has slightly decreasing output voltage with increasing input voltage.  This novelty results in improved regulation and improved PSRR.

                    There is a simplified schematic of the two-cell voltage regulator with improved PSRR in fig.1.   Voltage dVbe is created by the emitter area difference of transistors Q1,Q2, this dVbe voltage is applied on resistor string R5,R3 and creates IPTAT current.  This IPTAT current flows through the string R2,R5,R3 and BE diode of Q4 and develops the Vbgref voltage which is multiplied by the OUT stage to the required voltage on the OUT pin.  The current ipsrr is increasing if the Vcc goes up.  This current is fed into the upper terminal of resistor R3 which results into decreasing of Vbgref voltage – this is in fact degradation of the PSRR performance of BG reference cell, how...