onsemi FAN2502S33X

Overview

FAN2502S33X from Fairchild Semiconductor is a 3.3 V fixed-output CMOS low-dropout (LDO) voltage regulator in SOT-23-5 package, delivering 150 mA output current with 150 mV dropout at full load, 25 µA ground current at 150 mA, and enable/shutdown control - designed for power management in portable battery-powered systems such as cellular handsets and notebook computers.

For engineers reviewing the FAN2502S33X datasheet, pinout, applications, or equivalent options, key selection criteria include its ultra-low quiescent current, thermal shutdown protection, bypass-capacitor–enabled noise reduction, compatibility with wide-ESR output capacitors, and fixed 3.3 V output with BYP pin functionality.

Technical Context

The FAN2502S33X employs a P-channel MOSFET series pass element with ~1 Ω on-resistance, enabling low dropout performance across load, input voltage, and temperature variations. Its CMOS error amplifier features low input bias current and references an internal 1.32 V bandgap, ensuring stable regulation without external resistor networks for fixed-voltage variants.

Pin 4 is configured as BYP (bypass), accepting a 470 pF capacitor to suppress output noise; loop stability is maintained with output capacitors ranging from 1 µF to >10 µF and ESR from 10 mΩ to 10 Ω. Thermal protection shuts down the output at 150 °C junction temperature and re-enables automatically upon cooling.

Key Specifications

Pinout & Package

SOT-23-5 surface-mount package (EIAJ SC-74A), 2.9 mm × 1.6 mm footprint, 1.1 mm height, with exposed pad not electrically connected. Designed for compact layout and moderate thermal dissipation on standard FR-4 PCBs.

Key Features

Applications

Equivalent & Alternatives

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

Compared with FAN2502S33X, MCP1700T-3302E/MB offers lower shutdown current but no noise-suppression capability, while TPS76333DBVR provides higher accuracy at the cost of 3.4× higher active ground current - making FAN2502S33X optimal for portable systems needing both low-noise and low-quiescent-power 3.3 V regulation.

Availability

FAN2502S33X is available at Aetrix Electronics and suitable for cellular handset power management, notebook subsystem regulation, portable camera sensor biasing, and PDA application processor core supply requiring stable component supply, long-term lifecycle support, and consistent parametric performance.

Supply support for FAN2502S33X 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 semiconductor company specializing in power management, analog, and discrete components before its acquisition by ON Semiconductor in 2016.

The FAN2502/FAN2503 family was developed for ultra-low-power, space-constrained portable electronics - emphasizing micropower operation, thermal resilience, and flexible pin configurations (ADJ/BYP/ERR) across a single platform.

FAQ

What is the maximum input voltage rating for the FAN2502S33X?

The FAN2502S33X supports an absolute maximum input voltage of 7 V, with recommended operating range from 2.7 V to 6.5 V. Exceeding 7 V risks permanent damage per Absolute Maximum Ratings. Within the 2.7–6.5 V range, the device maintains 3.3 V output regulation, 150 mV dropout at full load, and stable PSRR performance - making it compatible with single-cell Li-ion (3.0–4.2 V) and regulated 5 V system rails.

Does the FAN2502S33X require an external bypass capacitor, and what value is recommended?

Yes, the FAN2502S33X uses Pin 4 as BYP and benefits from a 470 pF capacitor connected between BYP and GND to reduce output noise. Values from 470 pF to 10 nF are supported, but 470 pF is the manufacturer-recommended value for optimal noise suppression in the 10 Hz–1 kHz band. Ceramic or film capacitors with low leakage are required to avoid accuracy degradation; tantalum types are not recommended due to leakage risk.

How does the enable function operate on the FAN2502S33X, and what happens to ground current during shutdown?

The EN pin (Pin 3) enables regulation when pulled to ≥2.0 V and disables output when ≤0.4 V. During shutdown, the FAN2502S33X reduces ground current to less than 1 µA - verified across -40°C to +125°C. This ultra-low shutdown current preserves battery charge in standby modes. Leaving EN floating causes erratic behavior; tying it directly to VIN ensures always-on operation unless actively controlled.

Can the FAN2502S33X be used with aluminum electrolytic output capacitors, and what ESR range is acceptable?

Yes, the FAN2502S33X is explicitly designed to remain stable with aluminum electrolytic, tantalum, and multilayer ceramic output capacitors. Its loop compensation accommodates ESR values from 10 mΩ up to 10 Ω - far wider than conventional LDOs. A minimum 1 µF capacitance is required; aluminum electrolytics meeting this value and ESR spec will provide reliable regulation across temperature and load transients without oscillation.

What thermal protection behavior does the FAN2502S33X exhibit under sustained overload conditions?

The FAN2502S33X incorporates thermal shutdown that activates at 150 °C junction temperature, disabling VOUT until die temperature falls below the threshold. It then auto-re-enables - no external reset is needed. This protects against permanent damage during PCB layout with insufficient copper area or ambient temperatures exceeding +85 °C. The SOT-23-5 package has θJA ≈ 220 °C/W on minimal copper; adding 1–4 in² ground plane reduces θJA to 130–180 °C/W for improved thermal headroom.