Diodes Incorporated AP2129K-3.3TRG1

Overview

AP2129K-3.3TRG1 from Diodes Incorporated is a 300mA, fixed-output 3.3V CMOS low-dropout (LDO) regulator in SOT-23-5 package, featuring 60µA typical quiescent current, 60µV_RMS output noise, ±2% output voltage accuracy, and 170mV dropout at 300mA load. It delivers stable power to noise-sensitive analog and RF circuitry in portable electronics.

For engineers reviewing the AP2129K-3.3TRG1 datasheet, AP2129K-3.3TRG1 pinout, AP2129K-3.3TRG1 application, or AP2129K-3.3TRG1 equivalent, key selection criteria include ultra-low noise performance, active-high shutdown control, ceramic capacitor compatibility (1µF input/output), thermal shutdown with 30°C hysteresis, and operation across –40°C to +85°C ambient.

Technical Context

The AP2129K-3.3TRG1 integrates a precision bandgap reference, error amplifier, and PMOS pass transistor in a CMOS process, enabling low dropout and minimal quiescent current. Its internal soft-start circuit limits inrush current with a 50µs ramp time, while the 60Ω on-chip discharge MOSFET ensures rapid VOUT decay during shutdown.

It employs foldback current limiting and thermal shutdown at +165°C with +30°C hysteresis for robust fault protection. The device achieves 65dB PSRR at 1kHz and 45dB at 10kHz under 1V_P-P ripple, supporting high-PSRR requirements in mixed-signal systems without external compensation.

Key Specifications

Pinout & Package

SOT-23-5 package: 2.9mm × 2.8mm × 1.3mm body, surface-mount, RoHS-compliant, green finish. Thermal resistance θ_JA = 250°C/W (no heatsink).

Key Features

Applications

Equivalent & Alternatives

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

Compared with MCP1700T-3302E/TT and XC6206P332MR-G, the AP2129K-3.3TRG1 uniquely combines 300mA capability, active-high shutdown with auto-discharge, and 60µV_RMS noise-making it optimal for battery-powered systems requiring both low-noise analog power and intelligent power sequencing.

Availability

AP2129K-3.3TRG1 is available at Aetrix Electronics and suitable for wireless sensor nodes, USB peripheral designs, industrial PLC I/O modules, and portable medical monitors requiring stable component supply with full traceability and long-term lifecycle support.

Supply support for AP2129K-3.3TRG1 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 semiconductor company specializing in discrete, analog, and mixed-signal ICs, with design, manufacturing, and distribution operations across Asia, the Americas, and Europe.

The AP2129 series belongs to Diodes' high-performance LDO portfolio, engineered specifically for battery-powered and noise-critical applications demanding ultra-low noise, low IQ, and fast transient response in compact packages.

FAQ

What is the minimum input voltage required for stable 3.3V output at 300mA?

The AP2129K-3.3TRG1 requires VIN ≥ 3.47V (3.3V + 170mV max dropout) for full 300mA output. At lower loads, dropout decreases - e.g., 80mV at 10mA - allowing operation down to 1.8V input for light-load scenarios. Input must remain within 1.8V–6V absolute maximum range.

Can the AP2129K-3.3TRG1 be used with tantalum or aluminum electrolytic capacitors?

No - the AP2129K-3.3TRG1 is optimized for 1µF ceramic capacitors on both input and output. Tantalum or aluminum electrolytics exhibit higher ESR and inductance, which can degrade PSRR, cause instability, or increase output ripple beyond datasheet specifications. Ceramic capacitors are mandatory for guaranteed performance.

Does the shutdown pin require an external pull-down resistor?

No - the shutdown pin has an internal 3MΩ pull-down resistor. When left unconnected, it defaults to logic low (shutdown state). An external pull-up to VIN or a GPIO is required only to enable the device. This simplifies PCB layout and reduces component count in space-constrained designs.

How does the auto-discharge function behave during shutdown?

When the shutdown pin is driven low, the internal 60Ω MOSFET connects VOUT to GND, discharging the output capacitor rapidly. For a 1µF output cap, VOUT falls from 3.3V to <100mV in under 200µs. This prevents back-powering of upstream circuitry or unintended wake-up of downstream devices during system power-down sequences.