onsemi FAN1540DX

Overview

FAN1540DX from Fairchild Semiconductor is a 3.3V fixed-output, 1.3A low-dropout linear regulator in TO-252 package, designed for portable computing power rails where ultra-low quiescent current (1.0–2.0 mA), stable operation with 0 mΩ ESR output capacitors, and robust thermal shutdown (160°C) are critical. It delivers precise regulation (±2.5% over temperature/load) in disk drive circuits and notebook CPU core voltage sequencing.

For engineers reviewing the FAN1540DX datasheet, pinout, applications, or equivalent options, key selection criteria include dropout voltage (≤1.2 V at 1.3 A), load regulation (≤40 mV), ripple rejection (≥45 dB at full load), and compatibility with ceramic X7R input/output capacitors (22 µF/10 µF).

Technical Context

The FAN1540DX integrates a temperature-compensated bandgap reference, error amplifier, and current-limit/thermal-shutdown protection circuitry on a single die. Its internal architecture enables stable regulation without external compensation, even with zero-ESR ceramic capacitors.

It operates across 3.0–5.25 V input range and maintains ≤10% transient overshoot during 1 mA ↔ 1.3 A load steps and VIN power-on cycles. The device uses a single-stage pass transistor structure with no Kelvin sense pin-unlike the FAN1540MMPX variant-making it a simplified, cost-optimized solution for non-precision applications.

Key Specifications

Pinout & Package

Package: 3-Lead TO-252 (DPAK), thermally enhanced surface-mount package with exposed tab connected to GND for PCB heatsinking. θ_JC = 3°C/W enables high-power dissipation when mounted on ≥1 in² copper area.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MCP1700T-3302E/MB and NCP1117ST33T3G, the FAN1540DX uniquely balances 1.3 A capability, 1–2 mA quiescent current, and zero-ESR capacitor compatibility-making it irreplaceable in space-constrained, high-current portable LDO applications without sacrificing battery life or stability.

Availability

FAN1540DX is available at Aetrix Electronics and suitable for disk drive circuits, notebook computers, and desktop motherboard standby rails requiring stable component supply with full traceability and long-lifecycle support.

Supply support for FAN1540DX 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

Fairchild Semiconductor was a U.S.-based analog and power IC manufacturer, acquired by ON Semiconductor in 2016; known for high-reliability power management and discrete solutions.

The FAN1539/FAN1540 family was engineered specifically for portable computing power delivery-emphasizing low IQ, fast transient response, and capacitor flexibility to replace legacy regulators in space- and thermal-constrained designs.

FAQ

What is the maximum input voltage rating for the FAN1540DX?

The FAN1540DX has an absolute maximum input voltage of 10 V, but its recommended operating input range is 3.0 V to 5.25 V for optimal regulation and thermal performance. Exceeding 5.25 V increases power dissipation and risks exceeding the 150°C maximum junction temperature, especially at full 1.3 A load. Always refer to the thermal resistance (θ_JA) of your PCB layout when designing for higher input voltages.

Does the FAN1540DX require an output capacitor with minimum ESR?

No-the FAN1540DX is explicitly characterized and guaranteed stable with 0 mΩ ESR output capacitors, including X7R ceramic types. Unlike many LDOs, it does not require a minimum ESR for phase margin; adding series resistance degrades transient response and is unnecessary. Use 10 µF X7R (e.g., Murata GRM43ER71A226KE01B) placed within 5 mm of V_OUT and GND.

Can the FAN1540DX be used in place of the FAN1540MMPX?

No-the FAN1540DX and FAN1540MMPX are not interchangeable. The FAN1540MMPX is an 8-lead MLP package with a dedicated V_SEN pin for Kelvin sensing, enabling high-precision regulation; the FAN1540DX is a 3-lead TO-252 package with no sense pin and looser accuracy (±2.5% vs. ±1.5% for MMPX). Substitution would compromise regulation accuracy and disable remote sensing capability.

What is the thermal shutdown behavior of the FAN1540DX?

The FAN1540DX activates thermal shutdown at 160°C junction temperature and remains latched off until the die cools by ~15°C (hysteresis), re-enabling automatically at ~145°C. This prevents thermal cycling under persistent overload. During shutdown, output drops to near 0 V and quiescent current falls to microamps. Recovery time depends on PCB thermal mass and ambient conditions-typically 10–100 ms.

Is the FAN1540DX RoHS compliant and lead-free?

Yes-the FAN1540DX is RoHS compliant and lead-free per JEDEC J-STD-609. The TO-252 package uses matte tin (Sn) plating over copper leadframe, qualified for Pb-free reflow per J-STD-020 (peak 260°C for 10 seconds). Full compliance documentation-including substance declarations and test reports-is available upon request from Aetrix Electronics for audit-ready sourcing.