Pole-zero tracking compensation network for voltage regulators

A linear voltage regulator;

• comprising:
• an input for coupling to an input power source;
• an output for coupling to a load and a load capacitor;
• a pass switch configured to pass current from the input to the output based upon a pass control signal at a pass control terminal of the pass switch;
• an error amplifier configured to generate the pass control signal based upon a difference between a reference voltage and a feedback voltage which follows an output voltage of the linear voltage regulator, and configured to output the pass control signal at an error amplifier output;
• and
• a compensation network comprising:
• a compensation network input for coupling to the error amplifier output;
• a first resistance branch coupled to the error amplifier output and comprising a series resistor;
• a second resistance branch coupled in parallel to the first resistance branch and comprising a parallel resistor;
• and
• a current source configured to supply current to the compensation network,
• wherein the compensation network provides a variable impedance to the compensation network input, the variable impedance having a resistance that varies between a lower resistance based upon a resistance of the series resistor and an upper resistance based upon a resistance of the parallel resistor, the variable impedance being based upon a resistance control signal.

A method for frequency compensating a linear voltage regulator which includes an error amplifier and a compensation network coupled to an output of the error amplifier, the method comprising:

• sensing an output current of the linear voltage regulator;
• generating a switch control signal based upon the sensed output current;
• and
• applying the generated switch control signal to a resistance control switch of the compensation network, thereby controlling a level of current flow through a series resistor of the compensation network based upon the generated switch control signal, so as to vary an impedance of the compensation circuit such that a zero frequency of the compensation network varies linearly with the output current.