onsemi FAN2500S28X

Overview

FAN2500S28X from Fairchild Semiconductor is a 2.8 V fixed-output, 100 mA CMOS low-dropout (LDO) voltage regulator in SOT-23-5 package, featuring 100 mV dropout at 100 mA load, 25 µA ground current at 100 mA, enable/shutdown control, and thermal limiting - designed for power management in space-constrained portable electronics such as cellular handsets and notebook computers.

For engineers reviewing the FAN2500S28X datasheet, pinout, applications, or equivalent options, key selection criteria include its ultra-low quiescent current, fixed 2.8 V output with bypass-capacitor–optimized noise performance, SOT23-5 footprint compatibility, thermal shutdown behavior, and enable-controlled power-down capability under 1 µA.

Technical Context

The FAN2500S28X employs a P-channel MOSFET series pass element with ~1 Ω on-resistance, enabling low dropout voltage across load and temperature. Its error amplifier compares output voltage against an internal 1.32 V bandgap reference and drives the pass device to maintain regulation.

Pin 4 is configured as BYP (bypass), accepting a 470 pF capacitor to reduce output noise; it does not support adjustable output or error flag functionality. Loop stability is maintained over wide ESR ranges (10 mΩ to 10 Ω) in external output capacitors, supporting ceramic, tantalum, or aluminum electrolytic types.

Key Specifications

Pinout & Package

SOT-23-5 surface-mount package (JEDEC SC-74A), 2.9 mm × 1.6 mm footprint, 1.1 mm max 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 FAN2500S28X, MCP1700T-2802E/TT offers lower quiescent current but lacks noise-reduction capability and enable control, while XC6206P282MR-G provides deeper shutdown but omits the BYP function essential for high-fidelity analog supply rails.

Availability

FAN2500S28X is available at Aetrix Electronics and suitable for cellular handsets, portable cameras, and notebook subsystems requiring stable component supply, consistent parametric performance, and long-term lifecycle support.

Supply support for FAN2500S28X 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 FAN2500 family was developed for ultra-low-power, space-constrained portable electronics - specifically targeting GSM/TDMA handsets, PDAs, and notebook computers needing micropower LDOs with robust capacitor compatibility and thermal resilience.

FAQ

What is the maximum input voltage rating for the FAN2500S28X?

The FAN2500S28X has 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. The 2.7–6.5 V window ensures reliable regulation across single-cell Li-ion (3.0–4.2 V), Li-poly, or dual-cell alkaline inputs while maintaining 100 mV dropout margin at full load.

Does the FAN2500S28X support adjustable output voltage?

No, the FAN2500S28X does not support adjustable output voltage. It is a fixed 2.8 V variant with pin 4 configured as BYP (bypass), not ADJ. Only the base FAN2500 (without suffix) or FAN2500SX part numbers provide the ADJ pin for external resistor-divider programming. Attempting to use FAN2500S28X in adjustable configurations will result in incorrect or unstable output.

What capacitor values are recommended for the BYP pin on the FAN2500S28X?

A 470 pF ceramic capacitor is the standard recommendation for the BYP pin of the FAN2500S28X to optimize noise performance. Values from 470 pF to 10 nF are acceptable depending on application sensitivity; however, higher values may degrade transient response. Use X7R or NP0/C0G dielectrics for low leakage and stable capacitance over temperature - avoid Y5V due to voltage coefficient drift.

How does thermal shutdown behave on the FAN2500S28X during continuous overload?

The FAN2500S28X enters thermal shutdown at 150 °C junction temperature and remains disabled until die temperature falls below the hysteresis threshold (~140 °C), then automatically resumes regulation. During sustained overload, this can cause thermal cycling. To prevent instability, pair with adequate PCB copper area (≥1 in²) and use the EN pin to force shutdown if fault conditions persist - reducing power dissipation to <1 µA × V_IN.

Can the FAN2500S28X replace the FAN2501S28X in a design?

No, the FAN2500S28X cannot directly replace the FAN2501S28X because pin 4 serves different functions: BYP (capacitor connection) in FAN2500S28X versus ERR (open-drain error flag) in FAN2501S28X. Swapping them would disconnect the error monitoring circuit or leave the BYP node floating, degrading noise performance. Both share identical electrical specs except for pin 4 functionality and associated internal circuitry.