US 7,612,549 B1Granted

Low drop-out regulator with fast current limit

AssigneeAdvanced Analog Technology, Inc.

InventorsShun-Hau Kao, Mao-Chuan Chien

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Abstract

An LDO with fast current limit includes P-type transistor, an error amplifier, an adjustable reference voltage circuit for generating an adjustable reference voltage, and an N-type transistor. The P-type transistor includes a first end coupled to the input voltage source, a second end for outputting an output voltage source, and a control end for receiving a current control signal in order to control the current of the output voltage source. The error amplifier generates the current control signal according to the reference voltage and a voltage divided from the output voltage source. N-type transistor includes a first end coupled to the output end of the error amplifier, a second end coupled to the input voltage source, and a control end for receiving the adjustable reference voltage. When the N-type transistor is turned on, the voltage of the current control signal is clamped by the adjustable reference voltage.

Claims13

Dependent claims

A Low Drop-Out (LDO) regulator with fast current limit, comprising:

a first transistor, comprising:
a first end, coupled to an input voltage source;
a second end for outputting an output voltage source;
and
a control end for receiving a current control signal to control current of the output voltage source outputted from the second end of the first transistor;
an error amplifier, comprising:
a negative input end for receiving a reference voltage;
a positive input end for receiving a voltage divided from the output voltage source;
and
an output end, the error amplifier generating the current control signal through the output end of the error amplifier according to the reference voltage and the voltage divided from the output voltage source;
an adjustable reference voltage circuit for generating an adjustable reference voltage;
and
a second transistor, comprising:
a first end, coupled to the output end of the error amplifier;
a second end, coupled to the input voltage source;
and
a control end, coupled to the adjustable reference voltage circuit for receiving the adjustable reference voltage;
wherein when the second transistor is turned on, voltage of the current control signal is clamped by the adjustable reference voltage.

15 more elements

Dependencies are inferred from the claim text.