Low noise, low power, fast startup, and low drop-out voltage regulator

An integrated circuit voltage regulator, comprising:

• a filter;
• a reference amplifier that is coupled between a constant voltage reference and the filter, wherein a gain of the reference amplifier is adjustable to provide a reference voltage that is relatively equivalent to an output voltage of the integrated circuit voltage regulator;
• an error amplifier that compares a filtered reference voltage outputted by the filter to the output voltage for the integrated circuit voltage regulator;
• and
• a pass transistor that is coupled between an input voltage to the integrated circuit voltage regulator and the output voltage, wherein an output of the error amplifier is based on a comparison of the filtered reference voltage and the output voltage, and controls a conduction of the pass transistor, and wherein the controlling of the pass transistor's conduction maintains a substantially constant value for the output voltage with relatively low noise, wherein the filter includes:
• a capacitive element;
• and
• a resistive element, including:
• a first field effect transistor having at least a source, wherein a length of the first field effect transistor is substantially greater than a width of the first field effect transistor, and wherein the reference amplifier is coupled to the filter at the source of the first field effect transistor;
• and
• a second field effect transistor, wherein a width of the second field effect transistor is substantially greater than a length of the second field effect transistor.

A method for regulating an output voltage, comprising

• providing a constant voltage reference;
• employing a reference amplifier to provide a reference voltage that is based at least in part on the constant voltage reference;
• filtering noise from the reference voltage with a filter that is part of an integrated circuit with other components that provide a gain and the constant voltage reference;
• employing an error amplifier to perform a comparison of the filtered reference voltage and output voltage feedback to maintain a relatively constant output voltage of a pass transistor, wherein the filter includes a capacitive element, and a resistive transistor having a source, a drain, and a well, wherein the source is coupled to the well, and wherein the source and the drain are arranged to provide a resistive channel, wherein a length of the resistive transistor is substantially greater than a width of the resistive transistor, wherein the filter further includes a second transistor, and wherein a width of the second transistor is substantially greater than a length of the second transistor;
• and
• employing the reference voltage to drive the well of the resistive transistor.

An integrated circuit voltage regulator, comprising:

• a constant voltage reference;
• a reference amplifier that generates a reference voltage, wherein the reference voltage is an amplification of the constant voltage reference, and wherein a gain of the reference amplifier is adjustable to provide the reference voltage at a level that is relatively equivalent to an output voltage of the integrated circuit voltage regulator;
• a filter that suppresses noise and provides a filtered reference voltage based at least in part on the reference voltage, wherein the noise is substantially generated by the reference amplifier and the constant voltage reference, wherein the filter includes:
• a capacitive element;
• and
• a resistive element, including:
• a resistive transistor having at least a source that is arranged to receive the reference voltage from the reference amplifier, wherein a length of the resistive transistor is substantially greater than a width of the resistive transistor;
• and
• a second transistor, wherein a width of the second transistor is substantially greater than a length of the second transistor;
• an error amplifier that makes a comparison between the filtered reference voltage that is outputted by the filter and output voltage feedback from the integrated circuit voltage regulator;
• and
• a pass transistor that is coupled between an input voltage to the integrated circuit voltage regulator and the output voltage, wherein a conduction of the pass transistor is controlled by an output of the error amplifier to maintain a substantially constant value for the output voltage, and wherein the constant voltage reference, the reference amplifier, the filter, the error amplifier and the pass transistor are included in the integrated circuit voltage regulator.

A low noise micro power regulator controller, comprising:

• a reference voltage amplifier having at least an input and an output;
• an on-chip low-pass filter, including:
• a capacitive element;
• and
• a resistive element, including:
• a first transistor, wherein a length of the first transistor is substantially greater than a width of the first transistor;
• a second transistor, wherein a width of the second transistor is substantially greater than a width of the second transistor, and wherein the second transistor includes:
• a gate;
• a n-type well;
• a p-type source region in the n-type well, wherein the source region of the second transistor is connected to:
• the n-type well, the source of the second transistor, and to the output of the reference voltage amplifier;
• a p-type drain region in the n-type well of the second transistor, wherein the drain region of the second transistor is coupled to the MOS capacitor;
• and
• a current sink that is coupled to a drain of the first transistor;
• a pass transistor having at least a gate, a drain, and a source, wherein the source of the pass transistor is coupled to an input voltage node, and wherein the drain of the pass transistor is coupled to an output voltage node;
• and
• an error amplifier having at least a first input, a second input, and an output, wherein the first input of the error amplifier is coupled to the drain region of the second transistor, the second input of the error amplifier is coupled to the output voltage node, the output of the error amplifier is coupled to the gate of the pass transistor, and wherein the error amplifier has a gain of approximately one.