National Semiconductor Corporation

Shengming Huang

Andre Schouten

John J Gough

Robin Shields

A signal source generates a reference voltage, and a voltage regulator receives the reference voltage and generates an output voltage and current. During normal operation, a pass element in the voltage regulator generates the output voltage, and a sense element generates a sense voltage. A first voltage detector detects a short-circuit condition using the sense voltage. A second voltage detector deactivates the pass element in response to the detection of the short-circuit condition. The second voltage detector also detects removal of the short-circuit condition and automatically reactivates the pass element. The first voltage detector may detect the short-circuit condition by detecting a drop in the sense voltage. The second voltage detector may detect the removal of the short-circuit condition by applying a test current to a load. Both the first and second voltage sensors may not consume any direct current power during normal operation of the voltage regulator.

Regulator short-circuit protection circuit and method

An oscillation sensor for a regulator that provides dynamic control of a connection/disconnection of a compensation capacitance. The compensation capacitor is disconnected under normal operation and is automatically connected if oscillation is detected in the output and regulator's error amplifier. In this way, oscillations are stopped in the regulator almost immediately after it occurs. Also, once the circuit is stable again, the compensation capacitor is quickly disconnected again. Consequently, the compensation capacitor does not adversely affect the overall performance of the regulator.

Oscillation sensor for linear regulation circuit

A low-dropout regulator is provided that includes a filter and a bandgap reference generator. The filter includes a resistive device and a capacitor. The bandgap reference generator is coupled to the filter and includes a resistive device controller. The resistive device controller is operable to control the resistive device in the filter. The bandgap reference circuit is operable to generate an unfiltered voltage reference, and the filter is operable to generate a filtered voltage reference based on the unfiltered voltage reference.

Low-dropout regulator

A low drop out (LDO) regulator that includes a novel error amplifier, which is arranged with a first stage that employs both NMOS and PMOS devices that are similarly doped in differential pairs and a second stage that operates with NMOS and PMOS devices in a push-pull arrangement. In addition to the error amplifier, the LDO regulator can also include a startup circuit coupled to an enable voltage, a reference filter circuit coupled to a reference voltage, an output circuit, a quiescent current control circuit, and a pulse generator circuit. Also, an internal RC network is provided to compensate for phase shift. The integrated operation of the components of the regulator enables stable and fast operation of an LDO regulator with no external capacitors connected to the input or output terminals.

Capacitor free low drop out regulator

A tail current source is provided. The tail current source may be used in amplifiers, in an error amplifier of an LDO, or the like, to achieve high PSRR. The tail current source includes a first current mirror, a capacitor, a resistive device, and a current mirror circuit. The current mirror circuit is operable to provide the tail current from an input current. The first current mirror is an n-type current mirror which diverts a small fraction of the DC current from the current mirror circuit. The capacitor and the resistive device are coupled in series with each other, and are coupled between VDD and the common gate node of the transistors in the n-type current mirror. Accordingly, the gates of the transistors in the first current mirror follow AC variations in VDD. This way, the effects of AC variations in VDD on the tail current are approximately cancelled.

Apparatus and method for a high PSRR LDO regulator

A voltage regulator circuit is arranged to provide a regulated output voltage from an unregulated input voltage. Also, the voltage regulator circuit includes a capacitor that is coupled between output and feedback nodes of the voltage regulator circuit. The capacitor may improve transient responses, output noise, and the power supply rejection ratio of the voltage regulator circuit during normal operation. During a start-up of the voltage regulator circuit, the capacitance between the output and feedback nodes is substantially eliminated or substantially reduced in order to reduce the time that it takes for the output voltage to reach a stable voltage level.

Voltage regulator circuit

A regulator system includes a power device and a sense device. During a normal operating mode, the power device is arranged to deliver current to a load, while the sense device is arranged to monitor the load current. An over-current mode is activated when the sensed load current exceeds a short-circuit current-limit. During the over-current mode, the power device is switched off such that the energy loss is minimized. Once the short-circuit condition is removed, the regulator system returns to the normal operating mode. The sense device is coupled to the load in such a way that the quiescent current of the regulator system does not rise with increasing load current. The regulator system is further arranged such that the short-circuit current-limit decreases automatically with increased operating temperature. The described regulator system has significantly reduced energy losses while also minimizing risks of thermal induced device failures during the short-circuit condition.

Over-current protection circuit

A startup circuit is used for producing a startup current for an analog integrated circuit device. The startup circuit includes a first portion including a diode component and a capacitance component. The first portion is configured to function as a power supply backup and generate a backup point voltage. The startup circuit includes a second portion including a current mirror component and a feedback component. The second portion is configured to generate a startup current using the backup point voltage, such that the startup current is provided based on the backup point voltage as a power supply voltage increases from a power off condition or a transient, thereby keeping an analog circuit alive during transients in power supply for fast recover and operation.

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Gourock, United Kingdom

Shengming Huang