AP2112 LDO Regulator: Datasheet, How-to-use, Application Analysis

AP2112 Description

The AP2112 is a CMOS process low dropout linear regulator with an enable function that delivers a guaranteed continuous load current of 600mA (min.). The AP2112 has fixed output voltages of 1.2V, 1.8V, 2.5V, 2.6V, or 3.3V. The LDO has 1.5 percent output accuracy and a very fast loop response, providing excellent performance when dealing with line and load transients. When the device is turned off, the AP2112 has an auto discharge function that connects the output to the ground via 60 of resistance. The regulator has low power consumption and is available in SOT25, SOT89-5, and SO-8 packages.  

AP2112 LDO Regulator Pinout and Pin Configurations

Pin Name

Supply input
VOUTRegulated output

Connected to ground
ENDecides the mechanism of output stage: enable/disable
NCNot connected

AP2112 LDO Regulator Specs & Features

Low dropout voltage: 3.3V

Input voltage: 2.5V~6V

Continuous Output current: 150mA

Low quiescent current: 55µA

PSRR: -65dB @1000Hz

Low standby current: 0.01µA

OTSD (On-amp Thermal Shutdown) protection

Stable with 1.0μF electrolytic capacitors

AP2112 Applications

Laptop computer

LCD monitor

Battery-powered equipment

SMPS post regulators

Microcontroller electronics projects

Other consumer electronic appliances

DC/DC modules

Power supplies for high-efficiency linear applications

Stationary DVD

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How to Use AP2112 LDO Regulator

Below is the typical application circuit of the AP2112 low dropout regulator. Attach the power supply to the VIN pin and we’ll get a 3.3V voltage output regulated by the device. The CIN and COUT in the figure are capacitors to ripple excessive noise of the connection. In this case, Easybom suggests using the X7R/X5R dielectric capacitors. 


Let’s take a look at another power analysis of the AP2112 application circuit.


On the one hand, the MPM3610 will regulate the input voltage to 3.9V, and a ferrite will remove the high-frequency noise of the output (the MPM3610 operates at 2MHz), and the AP2112 linear regulator will provide the 3.3V required by LibreServo. The AP2112 is a compact linear regulator capable of delivering 700mA without fuss, with a PSRR, or power supply rejection factor, that is quite good and a maximum voltage drop of 250mV that is only 50mV when it is delivering 150mA, very impressive characteristics.

The AP2112 allows up to 6V input, which would be a problem, but the problem is avoided by having the MPM3610 do the majority of the work of regulation. Even though it has an output current of up to 700mA, its encapsulation is very small. It has a maximum drop of only 250mV, but under normal conditions it is closer to 50-150mV, leaving more than enough margin up to the 3.9V that the MPM3610 regulates. Furthermore, it has a very good noise behavior with a relatively high PSRR.

About CMOS LDO Regulator


(The layout of LDO regulator using CMOS technology)

Using CMOS layout technology, CMOS LDO regulators have obvious benefits for portable electronic equipment and other low-power, space-sensitive applications. Its advance has contributed to the growing demand for LDO. The demand for wearable and mobile devices has skyrocketed. These devices’ only power source is a battery. However, using the battery for an extended time will result in an unstable voltage level. 

To address this issue, the CMOS linear voltage regulator was created. CMOS LDOs are preferred by lots of engineers and hobbyists for their small package size, outstanding power dissipation capability, automatic power-saving (APS) function, and high-speed load response for powering MCUs, MPUs, and other logic circuits.

AP2112 Alternative

TPS7A33, AMS1117, LP2985, RT9080, TPS7A26, TLV70433

AP2112 Voltage Regulator Dimensions


Download AP2112 Datasheet


1. What is the ground pin current in an LDO?

The difference between the input and output currents in the ground current (IGND), must include the quiescent current. The LDO efficiency is maximized when the ground current is low.

2. What is IQ in LDO?

It stands for the quiescent current, which is significant for battery-powered applications in which the low state of the value helps lengthen the battery life.

3. What does LDO mean?

LDO (Low Dropout) can operate with a small potential difference between input and output. It is also known as a low-loss or saturation type linear regulator. Operating at a lower potential difference allows for less energy loss and less heat generation.

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