Diodes Incorporated AP2126K-ADJTRG1

Overview

AP2126K-ADJTRG1 from Diodes Incorporated is a 300mA adjustable-output CMOS low-dropout (LDO) voltage regulator in SOT-23-5 package, featuring 170mV dropout at 300mA (V_OUT = 3.3V), ±2% output voltage accuracy, and 80µV_rms output noise. It operates from 3.0V to 6V input and supports adjustable output from 1.25V to 5.5V via external resistor divider, making it suitable for precision power rails in portable computing and datacom systems.

For engineers reviewing the AP2126K-ADJTRG1 datasheet, AP2126K-ADJTRG1 pinout, AP2126K-ADJTRG1 application, or AP2126K-ADJTRG1 equivalent, key selection criteria include low-noise regulation for RF/analog circuitry, soft-start timing (50µs), shutdown control with 0.1µA standby current, and compatibility with 1µF ceramic input/output capacitors.

Technical Context

The AP2126K-ADJTRG1 uses a CMOS pass transistor architecture with internal 1.25V reference and feedback loop controlled via ADJ pin. Its shutdown logic accepts 0–0.4V "Low" and 1.5–6V "High", enabling precise system-level power sequencing.

Thermal protection activates at +165°C with +30°C hysteresis, and overcurrent limiting caps output at 50mA during short-circuit events. The integrated 60Ω discharge MOSFET ensures rapid V_OUT decay upon shutdown, critical for multi-rail sequencing integrity.

Key Specifications

Pinout & Package

SOT-23-5 surface-mount package with 2.82mm × 1.70mm footprint, 1.3mm height, and thermal resistance θ_JA = 250°C/W.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar adjustable LDO regulator applications.

Compared with AP7361A-33SG-7 and MCP1703T-3302E/MB, the AP2126K-ADJTRG1 uniquely combines adjustable output, 50µs soft-start, and 80µV_rms noise-making it optimal for mixed-signal systems where flexibility, transient response, and analog performance are jointly critical.

Availability

AP2126K-ADJTRG1 is available at Aetrix Electronics and suitable for notebook computers, datacom modules, and wireless sensor nodes requiring stable component supply, RoHS-compliant packaging, and consistent parametric performance across temperature.

Supply support for AP2126K-ADJTRG1 includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Diodes Incorporated is a global manufacturer of discrete semiconductors and analog ICs, specializing in high-reliability power management, signal integrity, and protection solutions for industrial, computing, and communications markets.

The AP2126 series belongs to Diodes' precision LDO portfolio, engineered specifically for battery-powered and noise-sensitive applications demanding ultra-low quiescent current, high PSRR, and fast transient response.

FAQ

What is the minimum input voltage required for AP2126K-ADJTRG1 to regulate a 3.3V output?

The minimum input voltage is determined by dropout voltage plus desired output: 3.3V + 0.17V = 3.47V. With 3.0V minimum rated input, the device sustains regulation down to 3.47V input at full 300mA load. At lighter loads, regulation begins as low as 3.0V due to reduced dropout.

Can AP2126K-ADJTRG1 be used with tantalum output capacitors instead of ceramic?

No. The datasheet explicitly specifies compatibility only with low-ESR ceramic capacitors (≥1µF). Tantalum capacitors exhibit higher ESR and potential instability risks with this LDO's compensation design, which may cause oscillation or poor transient response.

How does the ADJ pin function in setting output voltage?

The ADJ pin connects to the center node of an external resistor divider (R1–R2) between VOUT and GND. Internal circuitry holds ADJ at 1.25V, so VOUT = 1.25V × (1 + R1/R2). R2 must be ≤200kΩ to ensure sufficient bias current; typical values are R2 = 10kΩ and R1 = 22kΩ for 3.3V output.

Is thermal shutdown latched or auto-recovering?

Thermal shutdown is auto-recovering with +30°C hysteresis. When junction temperature exceeds +165°C, regulation halts; output resumes once temperature falls below +135°C. This prevents repeated cycling during marginal thermal conditions while ensuring safe recovery without manual reset.