Diodes Incorporated AP2128K-2.5TRG1

Overview

AP2128K-2.5TRG1 from BCD Semiconductor Manufacturing Limited is a fixed-output 2.5V, 300mA CMOS low-dropout regulator with 170mV dropout at full load, ±2% output voltage accuracy, 60µV_rms output noise, and 68dB PSRR at 1kHz. It operates from 2.5V to 6V input and integrates thermal shutdown, short-circuit protection, soft-start (50µs), and auto-discharge (60Ω). It powers precision analog rails in notebook computers and motherboard VRM post-regulation stages.

For engineers reviewing the AP2128K-2.5TRG1 datasheet, AP2128K-2.5TRG1 pinout, AP2128K-2.5TRG1 application, or AP2128K-2.5TRG1 equivalent, key selection criteria include dropout performance at 300mA, RMS noise floor under 100kHz, shutdown logic thresholds (0–0.4V low / 1.5–6V high), and compatibility with 1µF ceramic input/output capacitors.

Technical Context

The AP2128K-2.5TRG1 uses a PMOS pass transistor architecture enabling ultra-low dropout and minimal quiescent current (60µA typical). Its internal reference (0.8V) and error amplifier deliver tight line/load regulation (0.06%/V and 0.6%/A) across –40°C to +85°C ambient.

It features integrated shutdown control with active-low logic, internal 3MΩ pull-down resistor, and VOUT discharge MOSFET (R_DS(ON) = 60Ω) for rapid rail collapse. Thermal protection activates at 165°C with 30°C hysteresis, and short-current limit is fixed at 50mA.

Key Specifications

Pinout & Package

SOT-23-5 package: 2.95mm × 1.70mm × 1.30mm body, 0.95mm lead pitch, RoHS-compliant green finish (G1 suffix).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar fixed-output LDO applications.

Compared with XC6206P252MR and RT9193-25GB, AP2128K-2.5TRG1 uniquely balances ultra-low noise (60µV_rms), low dropout (170mV), active-low shutdown, and integrated VOUT discharge - making it optimal for space-constrained, battery-sensitive systems requiring fast power cycling and clean analog rails.

Availability

AP2128K-2.5TRG1 is available at Aetrix Electronics and suitable for notebook computers, motherboard power delivery, industrial sensor signal chains, and mobile baseband platforms requiring stable component supply with guaranteed long-term sourcing.

Supply support for AP2128K-2.5TRG1 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

BCD Semiconductor Manufacturing Limited is a Shanghai-based analog IC designer specializing in high-performance power management, LED drivers, and mixed-signal solutions for consumer, computing, and industrial markets.

The AP2128 series targets ultra-low-noise, high-PSRR LDO applications in portable and embedded systems where battery life, signal integrity, and thermal efficiency are critical design constraints.

FAQ

What is the minimum input voltage required for AP2128K-2.5TRG1 to maintain regulation at 300mA?

The minimum input voltage is 2.67V - calculated as VOUT + VDROP = 2.5V + 0.17V. Below this, the device enters dropout and output voltage declines linearly with input. The absolute minimum VIN rating is 2.5V, but regulation requires headroom above dropout.

Can AP2128K-2.5TRG1 be used with ceramic capacitors smaller than 1µF?

No - the datasheet specifies 1µF minimum for both CIN and COUT to ensure stability and transient response. Using smaller values risks oscillation or excessive overshoot during load steps, as confirmed by Figure 31–32 load transient waveforms.

Does the NC pin (Pin 5) require PCB routing or grounding?

No - Pin 5 is internally unconnected in the fixed-output AP2128K-2.5TRG1 variant. It must remain floating and un-routed on the PCB; connecting it to GND or any other net may cause unpredictable behavior or damage.

How does the auto-discharge function operate during shutdown?

When SHUTDOWN is pulled low (≤0.4V), the internal 60Ω MOSFET connects VOUT to GND, discharging the output capacitor. This collapses VOUT within ~100µs for a 1µF capacitor (t ≈ R×C = 60Ω × 1µF), meeting fast-power-cycle requirements in modern sleep-state architectures.