Diodes Incorporated AP7343D-18FS4-7B

Overview

AP7343D-18FS4-7B from Diodes Incorporated is a 300mA, 1.8V 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. Packaged in the X2-DFN1010-4 (Type B) footprint, it delivers stable power to RF supplies, camera modules, and portable media subsystems where low quiescent current (35µA) and fast load transient response are critical.

For engineers reviewing the AP7343D-18FS4-7B datasheet, AP7343D-18FS4-7B pinout, AP7343D-18FS4-7B application, or AP7343D-18FS4-7B equivalent, key selection criteria include dropout voltage (0.35V max at 300mA for V_OUT=1.8V), thermal shutdown threshold (+150°C), EN input logic thresholds (0.5V low / 1.3V high), and compatibility with 1µF ceramic input/output capacitors in space-constrained PCB layouts.

Technical Context

The AP7343D-18FS4-7B integrates a CMOS-based pass transistor with internal voltage reference, error amplifier, current limit, and thermal shutdown circuitry. Its enable input (EN) provides precise on/off control without external components, and the built-in discharge function (denoted by "D" suffix) actively pulls V_OUT to GND during shutdown to prevent back-powering of downstream circuitry.

This variant features a fixed 1.8V output, operates across 1.7V–5.25V input range, and maintains regulation under load transients up to 300mA with <±30mV load regulation. The X2-DFN1010-4 (Type B) package includes an exposed pad optimized for thermal dissipation via PCB copper area connected to GND.

Key Specifications

Pinout & Package

X2-DFN1010-4 (Type B) package: 1.0mm × 1.0mm, 0.4mm pitch, 4 active terminals + exposed thermal pad (EP). EP must be connected to GND via large copper pour for optimal thermal performance (R_θJB = 85.7°C/W).

Key Features

Applications

Equivalent & Alternatives

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

Compared with MCP1703T-1802E/MB and XC6219B182MR-G, the AP7343D-18FS4-7B uniquely combines discharge functionality, industry-leading 75dB PSRR, and the smallest 1.0mm×1.0mm footprint-making it optimal for space-constrained, multi-rail portable devices requiring clean, sequenced power delivery.

Availability

AP7343D-18FS4-7B is available at Aetrix Electronics and suitable for smartphone camera modules, RF transceiver bias rails, portable media player audio codecs, and wearable sensor hubs requiring stable component supply, long-term lifecycle support, and RoHS-compliant sourcing.

Supply support for AP7343D-18FS4-7B 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-performance power management, signal integrity, and protection solutions for consumer, industrial, and automotive markets.

The AP7343 series belongs to Diodes' precision LDO portfolio, engineered specifically for battery-powered portable electronics demanding ultra-low noise, high PSRR, and minimal footprint-addressing stringent requirements in camera, RF, and audio subsystems.

FAQ

What is the purpose of the "D" in AP7343D-18FS4-7B?

The "D" suffix denotes integrated output discharge functionality: when the EN pin is pulled low, an internal 30Ω N-channel MOSFET actively discharges the V_OUT capacitor to GND. This prevents back-powering of downstream circuitry and ensures predictable power-down behavior in multi-rail systems-critical for reliable power sequencing in smartphones and wearables.

Can AP7343D-18FS4-7B operate with only a 1µF output capacitor?

Yes-the AP7343D-18FS4-7B is internally compensated and stable with a minimum 1µF ceramic output capacitor (X5R/X7R, 0402 or larger). This enables ultra-compact layout in space-constrained applications. For improved load transient response under large current steps (e.g., 1mA ↔ 300mA), a 4.7µF capacitor is recommended, but not required for basic stability.

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

The X2-DFN1010-4 (Type B) package has R_θJA = 237°C/W (JEDEC standard board), while SOT25 achieves 179°C/W. However, the DFN's exposed pad enables superior thermal conduction when soldered to ≥25mm² GND copper area-reducing R_θJB to 85.7°C/W versus 79.2°C/W for SOT25. Thus, in real PCBs with proper layout, the DFN often delivers better thermal performance despite higher nominal R_θJA.

Is AP7343D-18FS4-7B suitable for automotive applications?

The AP7343D-18FS4-7B itself is not automotive-qualified. However, Diodes offers the pin- and function-compatible AP7343Q-18FS4-7B, which is AEC-Q100 Grade 1 qualified (−40°C to +125°C junction temperature) and manufactured in IATF 16949-certified facilities. For automotive use, specify the "Q" variant-not the standard "D" part.