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High PSRR apparatus for Linear Voltage Regulators

IP.com Disclosure Number: IPCOM000011834D
Publication Date: 2003-Mar-19

Publishing Venue

The IP.com Prior Art Database

Abstract

Key words: PSRR, Line Regulation, Linear Voltage Regulator, Low Voltage Background Voltage regulators used with portable battery-powered devices must have high Power Supply Rejection Ratio (PSRR), which guarantees an output voltage with good rejection to supply fluctuations and spikes. PSRR specifications are often given at the frequency of one kilo hertz (KHz), or in the form of a diagram (refer to Fig. 1) showing suppression (dB) versus frequency. Typical wireless applications manage Radio Frequency (RF) sections using multi band selection in combination with a frequency synthesizer, and a power supply reference having about 70 dB noise suppression. Unfortunately, such suppression, while typical of prior art, is not sufficient to guarantee good quality of signals under varying conditions. Furthermore, the voltage regulator circuits used must provide a precise voltage reference output independent of temperature, charge or power supply voltage variations. It is also desirable to provide increased power supply rejection without affecting the minimum voltage supply provided to the voltage regulator, or increasing silicon area by using a high device count solution.All of the prior art mentioned above suffer from at least several limitations including requiring supply voltages of more than two volts, and offering little improvement of PSRR at low frequency or when a low amount of load current is supplied by the regulator. Therefore, there is a need for a correction method and circuit to provide high PSRR of voltage regulators or regulator references that operate at low voltage and operating over a broad range of diverse supply voltages.