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Low Drop Out Voltage Regulator having a Low Noise Bypassed Band Gap Reference with Fast Enable Transient Response

IP.com Disclosure Number: IPCOM000007547D
Publication Date: 2002-Apr-04

Publishing Venue

The IP.com Prior Art Database

Abstract

Low Drop Out (LDO) voltage regulators having a low noise characteristic are becoming increasingly desirable in the consumer electronics market. Because the main source of noise in prior art voltage regulators is from the band gap circuit that is used, a large value capacitor Cbypass is often placed between the band gap and error amplifier to reduce noise. These bypass capcitors introduce other problems and are costly. Reducing the size of the bypass capacitor and the deleterious effects upon the circuit are one objetcive of the invention. This LDO, especially in cellular telephones, provides a faster enable transient response than prior art yet retains or improves noise rejection and suppression. An example of a new low noise band gap reference with pre-charge circuit, having a means to boost bias current of a reference error amplifier upon receiving an enable signal, is shown. There is not any appreciable overshoot or undershoot, because auxiliary charge current becomes the part of the regulation loop.