Diodes Incorporated AP7343D-35FS4-7B

Overview

AP7343D-35FS4-7B from Diodes Incorporated is a 300mA, 3.5V fixed-output low-dropout linear regulator with high PSRR (75dB at 1kHz), ultra-low output noise (60µVrms), ±1% output voltage accuracy, and enable-controlled shutdown. Built on a CMOS process, it delivers stable power to RF supplies and portable media subsystems where low quiescent current (35µA) and fast load transient response are critical.

For engineers reviewing the AP7343D-35FS4-7B datasheet, AP7343D-35FS4-7B pinout, AP7343D-35FS4-7B application, or AP7343D-35FS4-7B equivalent, key selection criteria include its X2-DFN1010-4 (Type B) package thermal resistance (RθJA = 237°C/W), discharge-enabled output behavior, dropout voltage of 0.22–0.29V at 300mA, and guaranteed operation across –40°C to +85°C ambient.

Technical Context

The AP7343D integrates a precision voltage reference, error amplifier, current-limit circuit, and thermal shutdown protection in a single CMOS LDO architecture. Its enable input (EN) provides precise on/off control with defined logic thresholds (V_IL ≤ 0.5V, V_IH ≥ 1.3V), and the built-in auto-discharge path (30Ω N-channel FET) actively pulls VOUT to GND during shutdown.

Designed for low-noise analog and RF supply rails, it achieves 75dB ripple rejection at 1kHz and maintains stability with minimal 1µF ceramic output capacitance. The device supports input voltages from 1.7V to 5.25V and delivers 3.5V output with ±1% accuracy over temperature and line/load variations.

Key Specifications

Pinout & Package

X2-DFN1010-4 (Type B) package: 1.0mm × 1.0mm, 0.4mm pitch, exposed thermal pad (EP) - optimized for space-constrained mobile PCBs and thermal performance via EP-to-GND copper area.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MCP1703T-3502E/MB and XC6210B352MR-G, the AP7343D-35FS4-7B uniquely combines 300mA drive, enable-controlled discharge, 75dB PSRR, and X2-DFN1010-4 footprint - making it the sole option for compact, high-performance RF and imaging power rails requiring fast, safe shutdown.

Availability

AP7343D-35FS4-7B is available at Aetrix Electronics and suitable for RF power amplifier bias, camera ISP core supplies, wireless adapter baseband regulation, and portable media player audio DAC power requiring stable component supply, long-term lifecycle support, and automotive-grade traceability.

Supply support for AP7343D-35FS4-7B 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 manufacturer of discrete semiconductors and analog ICs, specializing in high-efficiency power management, signal integrity, and protection solutions for consumer, industrial, and automotive markets.

The AP7343 series targets low-power portable electronics, delivering high PSRR and ultra-low noise in miniature packages to meet stringent EMI and battery-life requirements in smartphones, tablets, and wireless modules.

FAQ

What is the purpose of the exposed pad (EP) on the X2-DFN1010-4 package?

The exposed pad is a thermal dissipation feature, not an electrical connection. It must be soldered to a ≥25mm² copper area tied to GND to achieve the specified RθJB = 85.7°C/W. Leaving it unconnected degrades thermal performance by >40%, risking thermal shutdown under 300mA load at +85°C ambient.

Does AP7343D-35FS4-7B require an external discharge resistor?

No. The "D" suffix denotes integrated auto-discharge functionality: when EN is pulled low, a 30Ω internal N-channel FET connects VOUT to GND, actively discharging output capacitance. This eliminates the need for external resistors and ensures rapid, controlled shutdown in RF and imaging systems.

Can AP7343D-35FS4-7B operate with input voltage below 1.7V?

No. The absolute minimum input voltage is 1.7V per datasheet specifications. Operation below this threshold causes dropout, output regulation loss, and potential instability. For sub-1.7V applications, consider alternative regulators such as the AP7361D series with 0.8V minimum VIN.

How does the 60µVrms output noise specification impact RF applications?

This noise level corresponds to ≈–104dBc/Hz at 100kHz offset, directly limiting phase noise in VCOs and reciprocal mixing in receivers. In practice, it enables EVM <2.5% for 64-QAM LTE signals and supports 20MHz channel bandwidths without additional filtering in PA bias rails.