Voltage regulator structure that is operationally stable for both low and high capacitive loads

A regulator structure, comprising:

• a first differential amplifier having a first input coupled to a reference voltage node and having an output;
• a second differential amplifier having a first input coupled to the output of the first differential amplifier;
• a third differential amplifier have a first input coupled to the output of the first differential amplifier;
• a first pmos transistor having a gate coupled to an output of the second differential amplifier, the first pmos transistor having a drain coupled to a second input of the second differential amplifier and coupled to a second input of the first differential amplifier;
• a second pmos transistor having a gate coupled to an output of the third differential amplifier, the second pmos transistor having a drain configured to output a regulated voltage for coupling to an external load and coupled to a second input of the third differential amplifier;
• and
• a circuit configured to replicate the regulated voltage, output a replicated regulated voltage and couple the replicated regulated voltage to the drain of the first pmos transistor.

A system, comprising:

• a first regulator structure having an output configured to be coupled to a capacitive structure and supply power to a main circuit domain;
• a second regulator structure having an output configured to be coupled to supply power to a back-up circuit domain;
• a switching circuit selectively connecting the output of the first regulator structure to the output of the second regulator structure;
• wherein said second regulator structure comprises:
• a low gain voltage regulator circuit having an input coupled to receive a variable reference voltage and an output configured to provide a regulated output voltage;
• a load current sensing circuit configured to sense load current supplied by the low gain voltage regulator circuit;
• a replica voltage regulator circuit having an input coupled to receive said variable reference voltage and an output whose voltage is modified in response to the sensed load current by the load current sensing circuit;
• and
• a variable reference voltage generator having a first input coupled to receive a voltage reference, a second input coupled to receive the modified output voltage of the replica voltage regulator circuit and output configured to supply the variable reference voltage.

A regulator structure, comprising:

• a low gain voltage regulator circuit including a first differential amplifier having a first input and a second input coupled to receive a variable reference voltage, a first transistor driven by an output of the first differential amplifier and an output node coupled to the transistor and second input and configured to provide a regulated output voltage;
• a load current sensing circuit configured to sense load current supplied by the low gain voltage regulator circuit;
• a replica voltage regulator circuit having an input coupled to receive said variable reference voltage and an output whose voltage is modified in response to the sensed load current by the load current sensing circuit;
• and
• a variable reference voltage generator configured to generate said variable reference voltage.