Low dropout (LDO) voltage regulator with soft-start circuit
AssigneeSemiconductor Components Industries, LLC
InventorsVaclav Kotrc, Jan Jezik
Life of this patent
Estimating the term…
Abstract
According to an aspect, a low dropout (LDO) voltage regulator includes a differential amplifier, a pass transistor coupled to an output of the differential amplifier, where the pass transistor is configured to provide an output voltage of the LDO voltage regulator, and a soft-start circuit coupled to the differential amplifier. The soft-start circuit is configured to adjust a soft-start driving signal to control a slope of the output voltage based on the output voltage during a start-up operation of the LDO voltage regulator.
Claims18
A low dropout (LDO) voltage regulator comprising:
- a differential amplifier;
- a pass transistor coupled to an output of the differential amplifier, the pass transistor configured to provide an output voltage of the LDO voltage regulator;
- and
- a soft-start circuit coupled to the differential amplifier, the soft-start circuit configured to adjust a soft-start driving signal to control a slope of the output voltage based on the output voltage during a start-up operation of the LDO voltage regulator,
- the soft-start circuit including:
- a plurality of first transistors defining a first voltage threshold;
- a plurality of second transistors defining a second voltage threshold;
- a clamp transistor connected to the output of the differential amplifier;
- a clamp capacitor connected to the clamp transistor;
- and
- a current source selectively connected to the clamp capacitor via a switch.
A low dropout (LDO) voltage regulator comprising:
- a differential amplifier;
- a pass transistor coupled to an output of the differential amplifier, the pass transistor configured to provide an output voltage of the LDO voltage regulator;
- and
- a soft-start circuit coupled to the differential amplifier, the soft-start circuit including:
- a plurality of first transistors defining a first voltage threshold;
- a plurality of second transistors defining a second voltage threshold;
- a clamp transistor connected to the output of the differential amplifier;
- and
- a clamp capacitor connected to the clamp transistor, the clamp capacitor configured to be charged during a start-up operation of the LDO voltage regulator to control an increase of the output voltage,
- the soft-start circuit configured to cause the clamp capacitor to have a first voltage slope in a first phase of the start-up operation and a second voltage slope in a second phase of the start-up operation, the second voltage slope being different than the first voltage slope, at least one of the first phase or the second phase having a duration that is determined based on a value of the output voltage.
A method for operating a low dropout (LDO) voltage regulator, the method comprising:
- charging a soft-start circuit during a start-up operation of the LDO voltage regulator, the soft-start circuit including a clamp transistor connected to an output of a differential amplifier, and a clamp capacitor connected to the clamp transistor, the charging including:
- generating, in response to an enable signal, a first voltage slope on the clamp capacitor during a first phase of the start-up operation;
- generating, in response to the output voltage exceeding a first voltage threshold defined by a plurality of first transistors, a second voltage slope on the clamp capacitor during a second phase of the start-up operation, the second voltage slope being different than the first voltage slope;
- generating, in response to the output voltage exceeding a second voltage threshold defined by a plurality of second transistors, a third voltage slope on the clamp capacitor during a third phase of the start-up operation, the third voltage slop being different than the second voltage slope;
- and
- increasing an output voltage of the LDO voltage regulator based on the first voltage slope, the second voltage slope, and the third voltage slope.
Dependencies are inferred from the claim text.