Diodes Incorporated AP7343D-105FS4-7B

Overview

AP7343D-105FS4-7B from Diodes Incorporated is a 300mA, 1.05V fixed-output low-dropout linear regulator with high PSRR (75dB at 1kHz), ultra-low output noise (60µV_rms, 10Hz–100kHz), ±1% output voltage accuracy, and enable-controlled shutdown. Fabricated on a CMOS process, it delivers stable power to noise-sensitive RF and digital core rails in space-constrained portable electronics using the X2-DFN1010-4 (Type B) package.

For engineers reviewing the AP7343D-105FS4-7B datasheet, AP7343D-105FS4-7B pinout, AP7343D-105FS4-7B application, or AP7343D-105FS4-7B equivalent, key selection criteria include its 35µA quiescent current, 0.39V typical dropout at 300mA (V_OUT = 1.05V), integrated auto-discharge function, and thermal shutdown protection at +150°C - critical for battery-powered handheld systems requiring fast transient response and low standby power.

Technical Context

The AP7343D-105FS4-7B integrates a precision voltage reference, error amplifier, current-limit circuit, and thermal shutdown logic within a single CMOS LDO architecture. Its enable input (EN) provides precise on/off control with defined thresholds (V_IL ≤ 0.5V, V_IH ≥ 1.3V), and the built-in discharge path (enabled by the "D" suffix) actively pulls V_OUT to GND during shutdown to prevent back-powering of downstream circuitry.

It operates across a wide input range (1.7V to 5.25V), supports output currents up to 300mA, and maintains stability with minimal 1µF ceramic output capacitance. The X2-DFN1010-4 (Type B) package features an exposed pad optimized for thermal dissipation (R_θJA = 237°C/W), with pin 5 (NC) reserved and pin 4 (VIN) decoupled via a recommended 0.47µF input capacitor placed adjacent to the device.

Key Specifications

Pinout & Package

X2-DFN1010-4 (Type B) package: 1.0mm × 1.0mm, 0.4mm pitch, 4 active terminals + NC + exposed pad (EP). EP must be connected to GND via large copper area for optimal thermal performance but not used as sole GND electrode.

Key Features

Applications

Equivalent & Alternatives

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

Compared with AP7343D-105FS4-7B, the AP7361D offers higher current headroom at the expense of efficiency and noise performance, while the MCP1826 sacrifices critical discharge functionality and PSRR for broader input range - making the AP7343D optimal for compact, noise-critical, sequenced-power designs.

Availability

AP7343D-105FS4-7B is available at Aetrix Electronics and suitable for RF power amplifier bias, digital core supply, camera sensor analog rail, and wireless adapter baseband applications requiring stable component supply, consistent parametric performance, and long-term production continuity.

Supply support for AP7343D-105FS4-7B 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 leadership in power management, signal integrity, and precision timing solutions.

The AP7343 series belongs to Diodes' high-performance LDO portfolio designed specifically for space-constrained, battery-powered portable electronics demanding ultra-low noise, high PSRR, and intelligent power sequencing - including smartphones, tablets, and wireless communication modules.

FAQ

What is the purpose of the NC pin (PIN5) in the X2-DFN1010-4 package?

PIN5 is a no-connect terminal with no internal bond wire or silicon connection. It must remain unconnected in PCB layout - tying it to GND or VIN risks mechanical stress on the die attach or contamination during assembly. The datasheet explicitly prohibits using PIN5 as a functional node, and doing so may cause field failures under thermal cycling.

Does the AP7343D-105FS4-7B require an external discharge resistor?

No. The "D" suffix indicates integrated auto-discharge functionality: an internal NMOS transistor (R_ON ≈ 30Ω) connects VOUT to GND when EN is pulled low. This eliminates the need for external resistors, saves board space, and ensures predictable discharge time (~C_OUT × 30Ω), unlike passive RC solutions with variable timing.

Can the AP7343D-105FS4-7B operate with a 1.0µF output capacitor only?

Yes - the device is stable with a minimum 1.0µF X5R/X7R ceramic capacitor (≤100mΩ ESR) placed within 2mm of VOUT and GND pins. Larger capacitors (e.g., 4.7µF) improve load transient response but are not required for stability. Avoid tantalum or aluminum electrolytics due to ESR and aging effects that risk oscillation.

How does the thermal performance differ between X2-DFN1010-4 and SOT25 packages?

The X2-DFN1010-4 (R_θJA = 237°C/W) achieves lower junction temperature than SOT25 (R_θJA = 179°C/W) under identical conditions due to its exposed pad's superior thermal conduction to PCB copper. With a 25mm² GND pour, X2-DFN1010-4 sustains 300mA at +85°C ambient; SOT25 requires larger copper area or forced airflow to match this capability.