VOLTAGE REGULATOR

• US 20120286751A1
• Filed: 05/02/2012
• Published: 11/15/2012
• Est. Priority Date: 05/12/2011
• Status: Active Grant

• Current Assignee: Ablic Inc. (MinebeaMitsumi Inc.)
• Original Assignee: SII Semiconductor Corporation
• Inventors: Imura, Takashi, Sakaguchi, Kaoru
• Granted Patent: US 9,110,487 B2
• Time in Patent Office: Days
• US Class Current: 323/282
• CPC Class Codes: G05F 1/573 with overcurrent detector

Abstract

Provided is a voltage regulator including an overcurrent protection circuit, which does not need a test circuit. The voltage regulator has a configuration in which a reference voltage circuit includes an element that determines a reference voltage and an overcurrent protection circuit includes an element that determines a maximum output current, the element of the reference voltage circuit and the element of the overcurrent protection circuit having the same characteristics. Accordingly, there is a correlation between an output voltage before trimming and the maximum output current for overcurrent protection. Thus, a maximum output current before trimming can be estimated without performing evaluation by a test circuit.

Claims

1. A voltage regulator, comprising:

a reference voltage circuit for outputting a reference voltage;

a differential amplifier circuit for comparing the reference voltage and a voltage which is based on an output voltage, and controlling a gate voltage of an output transistor so that the output voltage becomes constant; and

an overcurrent protection circuit for detecting a flow of an overcurrent to the output transistor, and limiting a current of the output transistor, wherein the reference voltage circuit includes an element that determines the reference voltage and the overcurrent protection circuit includes an element that determines one of a maximum output current and a short-circuit current of the output transistor, the element of the reference voltage circuit and the element of the overcurrent protection circuit having the same characteristics.

2. A voltage regulator according to claim 1, wherein:

the reference voltage circuit comprises a first NMOS depletion transistor and a first NMOS transistor;

the overcurrent protection circuit comprises;

a sense transistor for sensing an output current of the output transistor;

a second NMOS depletion transistor including a gate and a drain which are short-circuited, for allowing a current to flow through the sense transistor; and

a second NMOS transistor which is current-mirror-connected to the second NMOS depletion transistor;

the element that determines the reference voltage comprises the first NMOS depletion transistor and the first NMOS transistor; and

the element that determines the one of the maximum output current and the short-circuit current of the overcurrent protection circuit comprises the second NMOS depletion transistor and the second NMOS transistor.