onsemi FAN2503S28X

Overview

FAN2503S28X from Fairchild Semiconductor is a 2.8 V fixed-output, 150 mA CMOS low-dropout voltage regulator with error-flag (ERR) functionality in SOT-23-5 package. It delivers 150 mV dropout at 150 mA load, 25 µA ground current at full load, and thermal shutdown protection. It is used in portable computing and mobile communication devices requiring precise, fault-aware power regulation.

For engineers reviewing the FAN2503S28X datasheet, pinout, applications, or equivalent options, key selection criteria include its open-drain ERR flag for output undervoltage detection (95% trip level), 2.8 V ±2% output accuracy, enable-controlled shutdown (<1 µA), and compatibility with low-ESR ceramic, tantalum, or electrolytic output capacitors (1 µF min).

Technical Context

The FAN2503S28X uses a P-channel MOSFET series pass element with ~1 Ω on-resistance and an internal 1.32 V bandgap reference to regulate output. Its error amplifier features wide ESR tolerance (10 mΩ–10 Ω), enabling stable operation across capacitor types without external compensation.

Pin 4 functions as an open-drain ERR flag that asserts LOW when V_OUT falls below 95% of nominal (2.66 V), with typical response time of 3 ms. Thermal protection activates at 150 °C junction temperature and auto-recovers upon cooling.

Key Specifications

Pinout & Package

SOT-23-5 surface-mount package (JEDEC SC-74A), 1.6 mm × 2.9 mm footprint, 1.1 mm height, with exposed pad not electrically connected.

Key Features

Applications

Equivalent & Alternatives

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

Compared with FAN2503S28X, MCP1700T-2802E/TT offers lower quiescent current but omits the diagnostic ERR function, while XC6206P282MR-G improves PSRR and shutdown current but removes fault visibility-making FAN2503S28X uniquely suited for safety-critical portable systems needing output health awareness.

Availability

FAN2503S28X is available at Aetrix Electronics and suitable for cellular phones, portable cameras, laptop subsystems, and PDAs requiring stable component supply with full lifecycle traceability and consistent parametric performance.

Supply support for FAN2503S28X 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; its legacy LDO portfolio remains widely deployed in portable electronics.

The FAN2502/FAN2503 family was designed specifically for space-constrained, battery-powered devices demanding micropower operation, low dropout, and integrated fault signaling-targeting GSM/TDMA handsets, notebooks, and portable imaging equipment.

FAQ

What is the exact output voltage tolerance and load regulation spec for FAN2503S28X?

The FAN2503S28X has a nominal output voltage of 2.8 V with ±2% initial accuracy over temperature and line conditions. Load regulation is specified at ≤2.0% across 0.1 mA to 150 mA output current, ensuring stable voltage delivery despite dynamic current demands in portable systems using FAN2503S28X.

Does FAN2503S28X require an external bypass capacitor like some other variants in the family?

No, FAN2503S28X does not use a bypass capacitor. Pin 4 is assigned as ERR (error flag), not BYP. The bypass capacitor (470 pF–10 nF) applies only to FAN2502-XX variants; FAN2503S28X relies on its open-drain ERR pin for fault reporting instead, and no external capacitor is needed at pin 4 for FAN2503S28X operation.

What is the minimum recommended output capacitor value and ESR range for stable operation of FAN2503S28X?

FAN2503S28X requires a minimum 1 µF output capacitor and operates stably across a wide ESR range of 10 mΩ to 10 Ω. This allows use of ceramic, tantalum, or aluminum electrolytic capacitors without compromising loop stability-unlike older LDOs that demand tight ESR windows. Ceramic X7R or Y5V types are preferred for size and cost efficiency in FAN2503S28X designs.

How does the ERR pin on FAN2503S28X behave during thermal shutdown?

During thermal shutdown, the ERR pin on FAN2503S28X asserts LOW (active) because V_OUT drops below 95% of nominal (2.66 V) due to output disablement. The pin remains LOW until the junction cools sufficiently for regulation to resume and V_OUT recovers above 2.66 V, at which point ERR returns HIGH. This behavior enables FAN2503S28X to signal both overcurrent and thermal faults via the same pin.

Can FAN2503S28X be used with an input voltage as low as 2.7 V while maintaining regulation?

Yes, FAN2503S28X supports input voltages down to 2.7 V, but regulation is only maintained if the input exceeds the dropout voltage plus output voltage. At 150 mA load, dropout is 150 mV, so minimum functional V_IN = 2.8 V + 0.15 V = 2.95 V. Thus, 2.7 V input is insufficient for regulation at full load; FAN2503S28X requires ≥2.95 V input to sustain 2.8 V output at 150 mA.