How to Select an LDO Regulator

Introduction

Low-dropout regulators provide a stable output voltage for analog, RF, sensor, processor, and embedded circuits. Selecting the correct LDO requires engineers to evaluate input voltage, dropout voltage, load current, noise, ripple rejection, stability and thermal performance.

Confirm the Input and Output Voltage

The input voltage must remain high enough above the output voltage for the regulator to maintain regulation. This required difference is determined by the LDO’s dropout voltage. Battery-powered designs should evaluate dropout performance across the full battery-discharge range.

Evaluate Output Current

The regulator must support the maximum continuous load and any temporary current peaks. Transient response is important when the load changes quickly, such as when a processor changes operating states or a communication circuit begins transmitting.

Compare Noise and PSRR

Output noise can affect sensitive analog, sensor, and RF circuits. Power-supply rejection ratio indicates how well the LDO reduces ripple or noise from the input supply. Both values should be reviewed at the frequencies relevant to the application.

Check Capacitor Requirements and Stability

LDO stability can depend on the value, type, and equivalent series resistance of the input and output capacitors. Engineers should follow the datasheet recommendations and evaluate capacitor variation across voltage, temperature, and tolerance.

Calculate Power Dissipation

Power dissipation is primarily determined by the difference between input and output voltage multiplied by load current. Excessive dissipation can raise the junction temperature and trigger thermal shutdown. Package thermal resistance, board layout, and ambient temperature must be considered.

Product Selection

Toshiba offers LDO regulators for stable power delivery across a range of voltage, current, and package requirements. Compare available products on the Toshiba LDO regulator product page.