Diodes Incorporated AP7343D-33FS4-7B

Overview

AP7343D-33FS4-7B from Diodes Incorporated is a 300mA, 3.3V 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 RF supplies and camera modules in space-constrained portable electronics using the X2-DFN1010-4 (Type B) package.

For engineers reviewing the AP7343D-33FS4-7B datasheet, AP7343D-33FS4-7B pinout, AP7343D-33FS4-7B application, or AP7343D-33FS4-7B equivalent, this LDO supports low-quiescent-current (35µA) operation, fast load transient response, and thermal shutdown protection - critical for battery-powered handheld communication equipment requiring clean, regulated 3.3V rails.

Technical Context

The AP7343D-33FS4-7B integrates a precision voltage reference, error amplifier, current-limit circuit, and NMOS pass transistor with built-in auto-discharge functionality activated upon EN deactivation. Its CMOS architecture enables low dropout (220mV typical at 300mA, V_OUT = 3.3V) and minimal quiescent current across –40°C to +85°C ambient.

It features active enable control (EN logic-high ≥1.3V, logic-low ≤0.5V), thermal shutdown at +150°C with +20°C hysteresis, and short-circuit current limiting (~55mA). The device is stable with 1µF ceramic output capacitors and requires no external compensation.

Key Specifications

Pinout & Package

X2-DFN1010-4 (Type B) package: 1.0mm × 1.0mm, 0.4mm pitch, exposed thermal pad (EP) - requires PCB copper area connected to GND 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 MCP1700-3302E/TO and XC6210B332MR-G, the AP7343D-33FS4-7B uniquely combines 300mA capability, 75dB PSRR, 60µV_rms noise, ±1% accuracy, and EN-activated auto-discharge in a 1.0mm × 1.0mm DFN - making it optimal for miniaturized, noise-sensitive, and rapidly cycled portable systems.

Availability

AP7343D-33FS4-7B is available at Aetrix Electronics and suitable for smartphone camera modules, Wi-Fi/Bluetooth RF supplies, portable media player audio codecs, and industrial handheld scanners requiring stable component supply, automotive-grade reliability (via AP7343Q variant), and long-term production continuity.

Supply support for AP7343D-33FS4-7B 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 solutions, with design centers across Asia, Europe, and the US, serving consumer, industrial, and automotive markets.

The AP7343 series targets low-power portable electronics, delivering high-PSRR, low-noise, and enable-controlled LDO regulation optimized for space-constrained, battery-operated devices demanding precision voltage rails.

FAQ

What is the function of the exposed pad (EP) on the AP7343D-33FS4-7B?

The exposed pad is a thermal enhancement feature, not an electrical terminal. It must be soldered to a large PCB copper area connected to GND to dissipate heat effectively - reducing junction temperature rise by up to 40°C under full load. It should never be used as the sole GND connection point for the device.

Does the AP7343D-33FS4-7B require an external pull-up resistor on the EN pin?

No external pull-up is required. When unused, EN may be tied directly to VIN to maintain permanent enable state. The internal EN input leakage is ±1.0µA, and the pin accepts standard 1.8V/3.3V logic levels - eliminating need for external biasing components in most microcontroller interfaces.

How does the auto-discharge feature behave during shutdown?

When EN is pulled low, an internal 30Ω NMOS switch connects VOUT to GND, discharging output capacitance. For a 10µF load, VOUT falls from 3.3V to <0.1V in <330µs. This prevents latch-up or undefined states in downstream logic and enables deterministic power sequencing in multi-rail systems.

Can the AP7343D-33FS4-7B operate with input voltages below 2.0V?

Yes - it supports VIN as low as 1.7V, enabling use with single-cell LiFePO₄ (2.5–3.65V) or fully discharged Li-ion (≥3.0V) batteries. At VIN = 3.52V, the 220mV typical dropout ensures stable 3.3V output at 300mA, extending usable battery runtime beyond competing LDOs with higher dropout.