Diodes Incorporated AP2127K-4.75TRG1

Overview

AP2127K-4.75TRG1 from Diodes Incorporated is a fixed-output 4.75V, 300mA CMOS low-dropout (LDO) regulator in SOT-23-5 package, featuring 140mV dropout at full load, ±2% output voltage accuracy, and 60μVRMS output noise. It operates from 2.5V to 6V input, supports ceramic capacitors as low as 1μF, and integrates thermal shutdown, short-circuit protection, and soft-start (50μs). It is used in notebook computers and motherboard power rails where stable, low-noise biasing of USB PHYs or PCIe reference clocks is required.

For engineers reviewing the AP2127K-4.75TRG1 datasheet, AP2127K-4.75TRG1 pinout, AP2127K-4.75TRG1 application, or AP2127K-4.75TRG1 equivalent, key selection criteria include dropout voltage at 300mA, PSRR at 1kHz/10kHz, quiescent current under active and shutdown modes, thermal resistance (θJA = 250°C/W), and compatibility with 1μF ceramic output capacitors.

Technical Context

The AP2127K-4.75TRG1 uses a PMOS pass transistor architecture enabling ultra-low dropout (140mV @ 300mA for VOUT = 4.75V) and high PSRR (63dB @ 1kHz, 45dB @ 10kHz). Its internal 0.8V bandgap reference feeds a precision error amplifier that maintains ±2% output regulation across -40°C to +85°C ambient temperature and 1mA–300mA load range.

It includes active shutdown control (logic-high enable), integrated 60Ω auto-discharge MOSFET, over-temperature protection (trip at +165°C), and current limiting (50mA short-circuit clamp). The device is optimized for stability with low-ESR ceramic capacitors and requires no external compensation.

Key Specifications

Pinout & Package

SOT-23-5 package: 2.9mm × 1.6mm × 1.1mm body, exposed pad for thermal enhancement (to be connected to GND), RoHS-compliant, halogen-free.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MCP1700T-4702E/TT and XC6209F472MR-G, the AP2127K-4.75TRG1 delivers superior PSRR (63dB vs. ≤65dB), lower dropout (140mV vs. ≥160mV), and integrated discharge functionality-making it optimal for noise-sensitive, power-sequenced, and thermally constrained applications.

Availability

AP2127K-4.75TRG1 is available at Aetrix Electronics and suitable for notebook computers, motherboard power management, and industrial sensor signal chains requiring stable component supply, long-term lifecycle support, and RoHS/Green compliance.

Supply support for AP2127K-4.75TRG1 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 manufacturer specializing in discrete, analog, and mixed-signal solutions for power management, signal integrity, and connectivity applications.

The AP2127 series belongs to Diodes' high-performance LDO portfolio, designed specifically for battery-powered and noise-sensitive systems demanding ultra-low noise, fast transient response, and minimal external components.

FAQ

What is the minimum input voltage required for AP2127K-4.75TRG1 to regulate at full 300mA load?

The minimum input voltage is calculated as VOUT + VDROP = 4.75V + 0.14V = 4.89V. Per datasheet specifications, this dropout value is guaranteed at TA = +25°C and IOUT = 300mA. At -40°C or +85°C, dropout may increase up to 300mV, requiring VIN ≥ 5.05V for guaranteed regulation across temperature.

Can AP2127K-4.75TRG1 be used with a 2.2μF X5R ceramic output capacitor?

Yes. The device is stable with any X5R/X7R ceramic capacitor ≥1μF and ESR < 100mΩ. A 2.2μF unit improves transient response and reduces output voltage undershoot during 300mA load steps, as confirmed in Figure 18 of DS36478 Rev. 7-2. No additional compensation is needed.

Does the NC/ADJ pin require external connection in the AP2127K-4.75TRG1 fixed-voltage variant?

No. The NC/ADJ pin is not internally bonded in fixed-output versions like AP2127K-4.75TRG1. Diodes Incorporated recommends leaving it unconnected or tying it to GND for mechanical stability and ESD robustness-no electrical function is affected either way.

How does the auto-discharge feature behave during shutdown?

When the Shutdown pin is driven low (<0.5V), the internal 60Ω MOSFET connects VOUT to GND, discharging the output capacitor. For a 10μF capacitor, VOUT falls from 4.75V to 10% (~0.48V) in approximately 1.4ms (t ≈ 2.3 × R × C = 2.3 × 60Ω × 10μF), preventing back-powering of upstream circuitry.