Part of the Day · AP2112K-3.3 — SOT25 (SOT-23-5) 3.3V 600mA LDO regulator (marking G3P)

Part of the Day · 2026-10-30

A small CMOS LDO widely used to drop 5V or a lithium cell (3.7V) to 3.3V. It delivers up to 600mA, and even at 600mA it needs only about 250mV (typ.) between input and output. It draws just 55µA when idle and can be switched off with the EN pin. The chip marking is G3P.

Actual size

↓ Actual size, left edge aligned to 0 on the ruler

One ruler tick = 1mm. On PC this is actual size on a 24-inch FHD monitor at 100% zoom; on iPhone it adjusts automatically. For other screens, use “Calibrate ruler” below.

Enlarged (SOT25 · top view · approx. 20×)

Pins 1 VIN (input) · 2 GND · 3 EN (high = on, low = off) · 4 NC (no connection) · 5 VOUT (output)

Package SOT25 · Marking G3P

Key specifications

Values are from the Diodes Incorporated datasheet.

Marking and pins

Marking code G3P · Pins 1 VIN (input) · 2 GND · 3 EN (high = on, low = off) · 4 NC (no connection) · 5 VOUT (output)

Typical uses

• 5V (USB) or lithium cell → 3.3V — Wi-Fi·Bluetooth modules, MCU boards
• Small power rails inside laptops and LCD monitors (datasheet application examples)
• Power for sensors and peripheral circuits switched on only when needed via EN

Companion & similar parts

• AP2112K-3.3TRG1 — Order part number — TR = tape & reel (7-inch, 3,000 pcs), G1 = Green (lead-free·halogen-free)
• AP2112K-1.8 · -2.5 · -2.6 · -1.2 — Other output voltages of the same series — chip markings G3M · G3N · G5N · G3L
• AP2112M-3.3 — SO-8 version of the same chip (VIN pin 8 · GND pins 6·7 · EN pin 5 · VOUT pin 1)
• AP2112R5-3.3 — SOT89-5 version of the same chip — chip marking G37G

Other makers' LDOs in the same SOT-23-5 size may use a different pin order, so always compare the pin tables before swapping. If you don't use EN, tie it straight to VIN to keep the regulator always on. Because of the internal 3MΩ pull-down, leaving EN open turns it off. When off, the output is discharged through an internal 60Ω. SOT25 has a thermal resistance of 184℃/W, so running 600mA continuously from 5V in to 3.3V out (about 1W) gets far too hot.