onsemi FAN2503S30X

Overview

FAN2503S30X from Fairchild Semiconductor is a 3.0 V fixed-output CMOS low-dropout (LDO) voltage regulator in SOT-23-5 package, delivering up to 150 mA output current with 150 mV dropout at full load, 25 µA ground current at 150 mA, and integrated enable/shutdown control and open-drain ERR flag for fault monitoring - deployed in portable computing and mobile communications power rails.

For engineers reviewing the FAN2503S30X datasheet, pinout, applications, or equivalent options, key selection criteria include its 3.0 V fixed output, ERR pin functionality for undervoltage detection, thermal shutdown at 150°C, ultra-low quiescent current, and compatibility with ceramic output capacitors down to 1 µF.

Technical Context

The FAN2503S30X uses a P-channel MOSFET series pass element with ~1 Ω on-resistance, enabling low dropout performance across temperature and load. Its error amplifier compares V_OUT against an internal 1.32 V bandgap reference and drives the pass device via CMOS circuitry.

Pin 4 functions as an open-drain ERR flag indicating output voltage drop below 95% of nominal (3.0 V), with typical response time of 3 ms. Thermal protection disables output above 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.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MCP1700T-3002E/MB, FAN2503S30X provides critical fault visibility via ERR flag and thermal recovery, while TLC7733IPW offers reset timing but mismatches the 3.0 V requirement and lacks thermal protection - making FAN2503S30X optimal for safety-aware portable power domains where undervoltage detection is mandatory.

Availability

FAN2503S30X is available at Aetrix Electronics and suitable for cellular phone power management, laptop subsystem regulation, portable camera sensor bias, and PDA application processor core applications requiring stable component supply, long-term lifecycle support, and traceable sourcing.

Supply support for FAN2503S30X 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, cost-effective power management solutions.

The FAN2502/FAN2503 family was designed specifically for micropower, low-dropout regulation in space- and battery-constrained portable electronics - emphasizing ultra-low I_Q, thermal resilience, and integrated diagnostics.

FAQ

What is the exact output voltage tolerance of the FAN2503S30X over temperature and load?

The FAN2503S30X delivers 3.0 V with ±2% accuracy across the full operating range of -40°C to +125°C junction temperature and 0.1–150 mA load current, as specified in the Electrical Characteristics table under ∆V_OUT parameter. This tolerance includes initial calibration, line regulation, and load regulation effects - ensuring reliable logic-level compatibility for 3.0 V I/O interfaces without external trimming.

Does the FAN2503S30X require an external bypass capacitor like the FAN2502 variants?

No, the FAN2503S30X does not use a bypass capacitor. Pin 4 is assigned as ERR (error flag), not BYP. The FAN2502-XX variants use pin 4 for bypass; the FAN2503-XX family replaces that function with an open-drain fault indicator. Therefore, no capacitor is connected to pin 4 on the FAN2503S30X - it must be pulled up externally via 100 kΩ for proper ERR signal interpretation.

What is the minimum input voltage required for the FAN2503S30X to maintain regulation at 150 mA load?

The minimum input voltage is calculated as V_OUT + V_DO = 3.0 V + 0.15 V = 3.15 V. At 150 mA load and 25°C, the dropout voltage is guaranteed ≤180 mV (max), so 3.18 V ensures regulation. For robust design across temperature and process variation, 3.2 V input is recommended - enabling operation from partially discharged single-cell Li-ion batteries (3.2–4.2 V range).

Can the FAN2503S30X be used without connecting the EN pin?

No - leaving the EN pin floating causes erratic operation per the datasheet. It must be actively driven: connect to V_IN (≥2.0 V) to enable regulation, or to GND (≤0.4 V) to shut down. If always-on operation is required, tie EN directly to V_IN with a short trace; do not leave unconnected, as leakage currents may cause unpredictable enable/disable behavior in the CMOS input stage of the FAN2503S30X.

How does the ERR flag on the FAN2503S30X behave during thermal shutdown?

During thermal shutdown, the FAN2503S30X disables the output but maintains ERR flag assertion: it remains LOW as long as V_OUT stays below 95% of 3.0 V (i.e., <2.85 V), which occurs both during thermal fault and input undervoltage. The ERR pin does not distinguish between root causes - it reflects only the output voltage condition. Once the die cools and regulation resumes, ERR returns HIGH if V_OUT recovers above 2.85 V.