Diodes Incorporated AP7343D-31FS4-7B

Overview

AP7343D-31FS4-7B from Diodes Incorporated is a 300mA low-dropout linear regulator with fixed 3.1V output, high PSRR (75dB at 1kHz), ultra-low output noise (60µVrms, 10Hz–100kHz), ±1% output voltage accuracy, and enable-controlled shutdown. It uses CMOS process technology and integrates current limiting, thermal shutdown, and auto-discharge functionality. Designed for RF supply rails in compact portable electronics, it operates from 1.7V to 5.25V input and delivers stable regulation under fast load transients.

For engineers reviewing the AP7343D-31FS4-7B datasheet, AP7343D-31FS4-7B pinout, AP7343D-31FS4-7B application, or AP7343D-31FS4-7B equivalent, key selection criteria include its 3.1V fixed output, X2-DFN1010-4 (Type B) package with exposed pad, 35µA quiescent current, 0.22–0.29V dropout at 300mA, and integrated discharge path for rapid VOUT decay during disable.

Technical Context

The AP7343D-31FS4-7B implements a CMOS-based LDO architecture with internal voltage reference, error amplifier, and N-channel pass transistor. Its enable input (EN) controls operation with logic-level thresholds (V_IL ≤ 0.5V, V_IH ≥ 1.3V), and the built-in discharge MOSFET (R_ON = 30Ω typical) actively pulls VOUT to GND when disabled.

It features thermal shutdown at +150°C with +20°C hysteresis, short-circuit protection limiting output current to ~55mA during VOUT-to-GND fault, and stable operation with ≥1µF ceramic output capacitance. The device supports wide input range (1.7–5.25V) and maintains ±1% output accuracy across -40°C to +85°C ambient temperature.

Key Specifications

Pinout & Package

The AP7343D-31FS4-7B is housed in the X2-DFN1010-4 (Type B) 1.0mm × 1.0mm, 0.4mm pitch, 4-pin package with exposed thermal pad (EP). The EP must be connected to PCB ground plane for optimal thermal performance (R_θJA = 237°C/W).

Key Features

Applications

Equivalent & Alternatives

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

Compared with AP7343D-31FS4-7B, the AP7361D-31YG-7 offers higher current headroom and better thermal performance in a larger package, while the XC6210B312MR-G trades discharge capability and tighter accuracy for marginally lower noise and higher IQ - making the AP7343D-31FS4-7B optimal for space-constrained, enable-driven, battery-powered RF and imaging systems.

Availability

AP7343D-31FS4-7B is available at Aetrix Electronics and suitable for RF power amplifier biasing, camera ISP power delivery, wireless communication module design, and portable media player audio subsystems requiring stable component supply, long-term lifecycle support, and traceable sourcing.

Supply support for AP7343D-31FS4-7B 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 emphasis on power management, signal integrity, and connectivity solutions for consumer, industrial, and automotive markets.

The AP7343 series belongs to Diodes' high-performance LDO portfolio, engineered specifically for noise-sensitive, battery-operated portable electronics requiring ultra-low IQ, fast transient response, and compact packaging.

FAQ

What is the purpose of the exposed pad (EP) on the AP7343D-31FS4-7B?

The exposed pad is a thermal dissipation feature, not an electrical terminal. It must be soldered to a PCB copper area connected to GND to reduce junction-to-ambient thermal resistance from 237°C/W to ~85°C/W. Leaving it unconnected or using it as sole GND connection degrades thermal performance and risks thermal shutdown under load.

Does the AP7343D-31FS4-7B require an external discharge resistor?

No. The "D" suffix indicates integrated auto-discharge functionality via a 30Ω internal NMOS transistor between VOUT and GND. When EN is pulled low, this transistor actively discharges the output capacitor, eliminating need for external components and ensuring rapid, controlled VOUT decay without floating nodes.

Can the AP7343D-31FS4-7B operate with a 3.0V input while delivering 3.1V output?

No. With a 3.1V output and minimum dropout of 0.22V at 300mA, the AP7343D-31FS4-7B requires VIN ≥ 3.32V to maintain regulation at full load. At 3.0V input, it enters dropout and cannot sustain 3.1V output - verify minimum input voltage using worst-case dropout (0.29V) plus output tolerance (3.1V × 1.01 = 3.131V) → VIN ≥ 3.421V.

How does the AP7343D-31FS4-7B handle short-circuit conditions?

Under VOUT-to-GND short, the device activates fold-back current limiting, clamping output current to ~55mA. Simultaneously, thermal shutdown triggers at +150°C junction temperature with +20°C hysteresis, allowing safe cooldown before automatic recovery. This dual protection prevents permanent damage during sustained faults or layout errors.