US 5,686,821 A · Stable low dropout voltage regulator controller

Abstract

A single-loop voltage regulator controller includes a high-gain transconductance amplifier that accommodates common mode inputs as low as its negative supply rail. The input stage of the amplifier produces a proportional to absoulte temperature (PTAT) input offset voltage. The transconductance amplifier's inverting input is connected to the circuit common, or negative supply rail, and a tap from a feedback network is connected to the amplifier's noninverting input. The feedback network provides, at this tap, a PTAT measure of the regulator's regulated output. The amplifier's output is connected to drive a noninverting driver which, in turn, is connected to drive the control terminal of the regulator's pass transistor. A compensation capacitor connected between the amplifier's output and the regulated output terminal ensures the regulator's stability even for relatively low level load impedances.

Claims30

Dependent claims

A low dropout voltage regulator controller for connection with a pass transistor to produce a low dropout voltage regulator, comprising:

a common supply terminal,
a control terminal connectable to the control terminal of a pass transistor,
an unregulated voltage input terminal connectable to a current conducting terminal of a pass transistor,
a regulated voltage output terminal connectable to another current conducting terminal of a pass transistor,
a single-loop feedback controller connected between said regulated voltage output terminal and said pass transistor control terminal, said feedback controller including a transconductance amplifier having an output, said feedback controller connected to provide a control signal which, when connected to said pass transistor control terminal produces a regulated output voltage at said regulated voltage output terminal which is substantially independent of the regulator's load and operating temperature, and
a pole-splitting compensation capacitor connected between the output of said transconductance amplifier and said regulated voltage output terminal which splits the regulator's poles to improve the stablilty of the regulator.

3 more elements

A low dropout voltage regulator having an unregulated voltage input terminal, a regulated voltage output terminal, and a common terminal, comprising:

a pass transistor having two current conducting terminals and one control terminal, one of said current conducting terminals connected to accept an unregulated input voltage, the other current conducting terminal connected to provide said regulated voltage output,
a noninverting driver connected to drive said control terminal of said pass transistor,
a differential amplifier having inverting and non-inverting inputs and an output, said amplifier being connected at its inverting input to a negative voltage supply and at its output to said control terminal of the pass transistor through said noninverting driver, and an input stage that accommodates common mode signals as low as the amplifier's negative supply rail, said input stage also connected to produce a PTAT input offset voltage,
a feedback circuit connected to sense the voltage across said regulated voltage output terminal and said common terminal and to provide at a tap terminal a PTAT signal that is representative of said voltage across said regulated voltage output and common terminals, said tap terminal connected to the noninverting input of said amplifier, and
a compensation capacitor connected from the output of said amplifier to said regulated voltage output terminal.

2 more elements

Dependencies are inferred from the claim text.

Stable low dropout voltage regulator controller

Life of this patent

Stable low dropout voltage regulator controller

Life of this patent

Abstract

Claims30