Diodes Incorporated AP2128K-4.75TRG1

Overview

AP2128K-4.75TRG1 from BCD Semiconductor Manufacturing Limited is a fixed-output 4.75V, 300mA CMOS low-dropout regulator with 140mV dropout at full load, ±2% output voltage accuracy, and 60µV_rms output noise. It features active shutdown (0.1µA standby current), thermal protection, and soft-start (50µs), designed for powering noise-sensitive analog rails in portable computing and motherboard power domains.

For engineers reviewing the AP2128K-4.75TRG1 datasheet, AP2128K-4.75TRG1 pinout, AP2128K-4.75TRG1 application, or AP2128K-4.75TRG1 equivalent, key selection criteria include dropout performance at 4.75V output, PSRR above 63dB at 1kHz, compatibility with 1µF ceramic capacitors, and thermal shutdown behavior under sustained 300mA load.

Technical Context

The AP2128K-4.75TRG1 uses a PMOS pass transistor architecture enabling ultra-low dropout (140mV @ 300mA) and high PSRR (63dB @ 1kHz, 45dB @ 10kHz) at its 4.75V fixed output. Its internal reference (0.8V) and error amplifier deliver ±2% output accuracy across –40°C to +85°C ambient.

It integrates logic-controlled shutdown with 0.4V max "low" threshold, auto-discharge MOSFET (R_DS(ON) = 60Ω), and thermal shutdown at 165°C with 30°C hysteresis-enabling safe operation in thermally constrained SOT-23-5 layouts without external supervision circuitry.

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 regulator applications.

Compared with XC6206P472MR-G and RT9193-47GB, the AP2128K-4.75TRG1 uniquely combines 300mA capability, 0.1µA shutdown, and 60Ω auto-discharge in a single SOT-23-5 footprint-making it optimal for space-constrained, battery-sensitive designs requiring full power-state control.

Availability

AP2128K-4.75TRG1 is available at Aetrix Electronics and suitable for notebook computers, motherboard power management, and industrial sensor nodes requiring stable component supply, long-lifecycle support, and RoHS-compliant packaging.

Supply support for AP2128K-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

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

The AP2128 series belongs to BCD's ultra-low-noise LDO product line, engineered specifically for noise-sensitive applications in portable computing and datacom infrastructure where PSRR and output cleanliness are critical.

FAQ

What is the minimum input voltage required for AP2128K-4.75TRG1 to maintain regulation?

The AP2128K-4.75TRG1 requires VIN ≥ 4.89V to sustain 4.75V output at 300mA load, based on its 140mV dropout specification. At lighter loads, regulation holds down to VIN = 4.75V + V_DROP(I_OUT), with dropout decreasing to <50mV below 50mA. Input must remain ≥2.5V for basic circuit operation, but regulation fails below the dropout threshold.

Can AP2128K-4.75TRG1 be used with ceramic output capacitors smaller than 1µF?

No-BCD specifies 1µF ceramic for both C_IN and C_OUT to ensure loop stability and transient response. Using <1µF risks oscillation or excessive output voltage deviation under load steps, as confirmed by stability analysis in the datasheet's Figure 31–32 load transient waveforms and recommended application circuit.

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

Pin 5 is unconnected internally in the AP2128K-4.75TRG1 fixed-output variant. BCD recommends leaving it floating; grounding is permissible but provides no functional benefit and may introduce unintended parasitic paths. No trace or thermal pad should be attached to this pin per mechanical drawing and functional block diagram.

How does the auto-discharge function behave during shutdown?

When SHUTDOWN is pulled low (<0.4V), the internal 60Ω MOSFET connects VOUT to GND, discharging the output capacitor. With a 1µF C_OUT, VOUT falls from 4.75V to <100mV in ~330µs (t ≈ 5 × R × C). This meets fast-power-down requirements in systems needing rapid rail collapse for sequencing or safety compliance.