Linear voltage regulator with isolated supply current

A linear voltage regulator comprising:

• an input voltage terminal for a regulator input voltage;
• an output voltage terminal for a regulator output voltage;
• a series pass field-effect transistor coupled between the input voltage terminal and the output voltage terminal;
• a buffer amplifier comprising a buffer output, a positive buffer input coupled to the output voltage terminal, and a negative buffer input coupled to the buffer output, the buffer amplifier powered by an independent voltage supply that is isolated from the input voltage terminal;
• a feedback divider network coupled between the buffer output and a ground terminal, the feedback divider network providing a scaled output voltage at a divider output;
• an analog-to-digital converter (ADC) comprising an analog voltage input coupled to the divider output to receive the scaled output voltage, and comprising a first digital output interface to provide a digital representation of the scaled output voltage, the ADC powered by the independent voltage supply;
• a digital processing core comprising a first digital input interface coupled to the first digital output interface, and comprising a second digital output interface, the digital processing core configured to generate a digital control output at the second digital output interface based on a difference between the digital representation of the scaled output voltage and a digital representation of a reference voltage, the digital processing core powered by the independent voltage supply;
• and
• a digital-to-analog converter (DAC) comprising a second digital input interface coupled to the second digital output interface, and comprising an analog output coupled to the transistor, the DAC configured to convert the digital control output into an analog control voltage and to provide the analog control voltage at the analog output, wherein the analog control voltage controls impedance of the transistor to adjust a regulator output voltage at the output voltage terminal, the DAC powered by the independent voltage supply.

A linear voltage regulator system comprising:

• an input voltage terminal for a regulator input voltage;
• an output voltage terminal for a regulator output voltage;
• a reference voltage terminal for a reference voltage;
• a series pass field-effect transistor coupled between the input voltage terminal and the output voltage terminal;
• and
• an error amplifier comprising an error output coupled to the transistor, a positive error input directly connected to the output voltage terminal to receive the regulator output voltage, and a negative error input coupled to the reference voltage terminal to receive the reference voltage, the error amplifier powered by an independent voltage supply that is isolated from the input voltage terminal, wherein output of the error amplifier is based on a difference between the reference voltage and the regulator output voltage, and wherein the output of the error amplifier controls impedance of the transistor to adjust the regulator output voltage at the output voltage terminal.