Low-Dropout Regulator (LDO)

Product Specifications

Technical details and manufacturing context for Low-Dropout Regulator (LDO)

Definition

A low-dropout regulator (LDO) is a linear voltage regulator used in power management to provide a stable, low-noise output voltage for sensitive electronic circuits. Unlike standard linear regulators, an LDO can operate with a very small difference between the input and output voltages, known as dropout voltage, which improves efficiency in battery-powered devices. The LDO is a critical component within Power Management Units (PMUs), where it supplies clean power to analog, RF, and digital loads that are susceptible to supply noise and voltage fluctuations.

The LDO uses a pass transistor (typically a MOSFET or BJT) controlled by a feedback loop. The feedback circuitry compares the output voltage to a reference and adjusts the pass transistor's conduction to maintain a constant output despite changes in input voltage or load current. The dropout voltage is the minimum input-output differential required for regulation; below this, the LDO loses regulation and the output follows the input minus a small drop.

Typical LDOs in this directory category offer output voltages from 1.2 V to 5.0 V, with fixed or adjustable versions. Output current ranges from 0.1 A to 1.5 A maximum continuous. Dropout voltage is 0.1 V to 0.5 V at full load. Line regulation is ±0.1 %/V, and load regulation is ±0.5 %. Quiescent current is 0.01 mA to 0.1 mA at no load, which is important for battery life. Operating temperature range is -40 °C to 85 °C. Input voltage range is 2.5 V to 6.0 V (absolute maximum). Output noise is 30 µVrms to 100 µVrms over a 10 Hz to 100 kHz bandwidth. Power supply rejection ratio (PSRR) is 50 dB to 80 dB at 1 kHz. A common package is SOT-23-5, though other packages are available.

Materials typically include silicon semiconductor, copper leadframes, and plastic encapsulation. These values are directory reference ranges; always verify model-specific specifications and standards with the legal manufacturer or supplier before procurement.

Working Principle

The LDO operates by using a pass transistor (typically MOSFET or BJT) controlled by feedback circuitry. The feedback loop compares the output voltage to a stable reference and adjusts the pass transistor's resistance to maintain a constant output voltage. When the input voltage or load current changes, the feedback loop responds by increasing or decreasing the transistor's conduction. The dropout voltage is the minimum input-output differential required for the feedback loop to maintain regulation. If the input voltage falls below this threshold, the LDO enters dropout and the output voltage tracks the input minus the transistor's saturation voltage. The pass transistor dissipates excess power as heat, so thermal management is important.

Common Materials

Silicon semiconductor, Copper, Plastic encapsulation

Technical Parameters

Parameter	Typical range	Notes & selection driver
Output Voltage	1.2–5.0 V	Fixed or adjustable versions available
Output Current	0.1–1.5 A	Maximum continuous current
Dropout Voltage	0.1–0.5 V	At full load; lower is better
Line Regulation	±0.1 %/V	Change in output per input voltage change
Load Regulation	±0.5 %	Change in output from no load to full load
Quiescent Current	0.01–0.1 mA	At no load; affects battery life
Operating Temperature	-40–85 °C	Junction temperature range
Input Voltage Range	2.5–6.0 V	Absolute maximum ratings
Output Noise	30–100 µVrms	10 Hz to 100 kHz bandwidth
Power Supply Rejection Ratio	50–80 dB	At 1 kHz; higher is better
Package Type	SOT-23-5	Other packages available

Ranges are indicative industry figures for RFQ preparation, not a supplier commitment. Confirm every value and standard with the legal manufacturer before ordering.

Components / BOM

Pass Transistor Part
Controls current flow from input to output to maintain constant output voltage

Material: Silicon semiconductor
Error Amplifier Part
Compares reference voltage with feedback voltage to control pass transistor

Material: Silicon semiconductor
Voltage Reference Part
Provides stable reference voltage for comparison

Material: Silicon semiconductor
Feedback Network Part
Divides output voltage for comparison with reference voltage

Material: Silicon semiconductor, thin-film resistors

Industry Taxonomies & Aliases

Commonly used trade names and technical identifiers for Low-Dropout Regulator (LDO).

Applied To / Applications

This component is essential for the following industrial systems and equipment:

Power Management Unit

View system integration details

Manufacturers of Low-Dropout Regulator (LDO)

1 company lists this product among what they make. Company figures are quoted from each company's own website; every card states where the relationship came from.

Silergy

Shanghai, CN

Also makes: Battery System, Battery Charger Controller, Power Management Module and 9 more

Listed on the company's own website · profile compiled by CNFX from public sources

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Frequently Asked Questions

What is dropout voltage in an LDO?

Dropout voltage is the minimum difference between input and output voltage required for the LDO to maintain regulation. If the input voltage drops below this threshold, the LDO cannot regulate and the output voltage will follow the input minus a small drop. Lower dropout voltage is generally better for efficiency, especially in battery-powered applications.

How does an LDO differ from a switching regulator?

An LDO is a linear regulator that dissipates excess power as heat, providing low output noise and simple design. A switching regulator uses inductors and switches to achieve higher efficiency, but generates more electrical noise. LDOs are often used for noise-sensitive analog circuits, while switching regulators are used for high-efficiency power conversion.

What are typical applications for an LDO?

LDOs are used in battery-powered devices, portable electronics, and systems requiring clean, stable supply voltages for analog, RF, or digital circuits. They are commonly found in power management units (PMUs) to provide separate voltage rails for different components, such as microcontrollers, sensors, and communication modules.

How do I select the right LDO for my application?

Consider the required output voltage and current, input voltage range, dropout voltage, quiescent current, output noise, and PSRR. Also check the operating temperature range and package type. Always verify the specifications with the manufacturer's datasheet and confirm compliance with relevant standards for your application.

Data Basis

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temperature:	-40°C to +125°C (typical operating range)
current capacity:	100mA to 5A (depending on package and design)
voltage differential:	0.2V to 5V (dropout voltage range)
output voltage accuracy:	±1% to ±3% (typical)

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