onsemi FAN1540MPX

Overview

FAN1540MPX from Fairchild Semiconductor is a 3.3V, 1.3A low-dropout linear regulator with ultra-low quiescent current (1.0–2.0 mA), ±2% output voltage accuracy over temperature and load, and stable operation with 0 mΩ ESR ceramic capacitors. It serves as a primary power rail regulator in portable computing systems requiring high transient response and thermal robustness.

For engineers reviewing the FAN1540MPX datasheet, pinout, applications, or equivalent options, key selection criteria include dropout voltage at 1.3A (≤1.2 V), thermal shutdown threshold (160°C), ripple rejection at 100mA (≥63 dB), and compatibility with compact 3×3 mm 6-lead MLP packaging for space-constrained PCB layouts.

Technical Context

The FAN1540MPX employs an internally trimmed, temperature-compensated bandgap reference and error amplifier topology to achieve 2.5% output voltage accuracy across 0°C to 125°C junction temperature and full load range. Its protection architecture integrates foldback current limiting and thermal shutdown with 15°C hysteresis to prevent cycling under sustained overload.

Stability is achieved without external compensation by supporting ceramic output capacitors down to 0 mΩ ESR-enabled by internal pole-zero cancellation. Transient response is optimized for ≤10% overshoot/undershoot during 1mA ↔ 1.3A load steps (tr/tf ≥ 1 µs) and VIN power-on events, verified with 22 µF input and 10 µF X7R output capacitors.

Key Specifications

Pinout & Package

Package: 3×3 mm, 6-lead MLP (Moisture Sensitivity Level 3, JEDEC MO-229 VEEA compliant). Exposed thermal pad on underside requires solder connection to PCB ground plane for θJC = 8°C/W.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MCP1826T-3302E/DB and TLS850F3TLE, the FAN1540MPX offers superior thermal resilience (160°C shutdown) and broader input range (up to 10 V), making it optimal for consumer portable platforms where input bus voltage varies and thermal margin is constrained.

Availability

FAN1540MPX is available at Aetrix Electronics and suitable for disk drive circuits, laptop motherboard I/O rails, and embedded industrial controllers requiring stable component supply with guaranteed long-term manufacturability.

Supply support for FAN1540MPX 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-performance LDOs, MOSFETs, and gate drivers targeting portable and computing markets.

The FAN1539/FAN1540 product line was engineered specifically for portable computing applications demanding ultra-low quiescent current, fast transient response, and thermal robustness in miniature MLP packages.

FAQ

What is the maximum input voltage rating for the FAN1540MPX?

The FAN1540MPX has an absolute maximum input voltage rating of 10 V, as specified in the Absolute Maximum Ratings table. Operation beyond this voltage risks permanent device failure. For reliable continuous operation, the recommended input range is 3.0 V to 7.0 V per the Electrical Characteristics test conditions-ensuring proper regulation, thermal stability, and specification compliance across temperature and load.

Does the FAN1540MPX require an external sense resistor for current limiting?

No, the FAN1540MPX does not require an external sense resistor for current limiting. It features fully integrated foldback current limiting with a nominal threshold of 3.3 A at 5.5 V input, as confirmed in the Electrical Characteristics table. This internal protection activates automatically during overload or short-circuit conditions without any external components, simplifying layout and reducing BOM count.

Can the FAN1540MPX be used with aluminum electrolytic output capacitors?

No, the FAN1540MPX is not designed for use with aluminum electrolytic output capacitors. The datasheet explicitly specifies stability with low-ESR ceramic capacitors (e.g., X7R type) down to 0 mΩ ESR. Aluminum electrolytics typically exhibit ESR > 100 mΩ and insufficient high-frequency response, which can cause oscillation or excessive transient overshoot. Use only 10 µF X7R ceramics such as Murata GRM43ER71A226KE01B as validated in the test circuit.

What is the thermal resistance (θJA) of the FAN1540MPX in its 3×3 mm MLP package?

The FAN1540MPX in the 3×3 mm 6-lead MLP package has a junction-to-ambient thermal resistance (θJA) that is layout-dependent-not a fixed value. The datasheet states θJC = 8°C/W, but θJA varies significantly with PCB copper area, layer count, and via density. On a minimal footprint, θJA may exceed 100°C/W; with optimized 1-in² copper pour and thermal vias, values as low as 20°C/W have been achieved. Designers must perform thermal simulation or measurement for their specific board.

Is the FAN1540MPX pin-compatible with the FAN1539MPX?

Yes, the FAN1540MPX and FAN1539MPX share identical 3×3 mm 6-lead MLP packaging and pinout (VIN, GND, VOUT, NC, GND, GND), as shown in the Pin Assignments diagram. However, they differ in output current rating (1.3 A vs. 1.0 A) and dropout voltage (1.2 V vs. 0.9 V max at full load). Substitution is electrically valid only if the 1.3 A capability and higher dropout of the FAN1540MPX meet the target application's thermal and regulation requirements.