onsemi FAN2558S10X

Overview

FAN2558S10X from onsemi is a fixed-output 1.0V, 180mA low-dropout linear regulator (LDO) in 5-lead SOT-23 package, featuring power-good (PG) open-drain output, ±1% output voltage accuracy, and 100µA ground current - designed for processor power-up sequencing and portable electronics requiring stable low-voltage bias.

For engineers reviewing the FAN2558S10X datasheet, pinout, applications, or equivalent options, key selection criteria include dropout voltage at 180mA load, PG delay timing (1–5ms), thermal shutdown behavior (150°C trip with 10°C hysteresis), ESR tolerance (0–300mΩ), and enable response time (30–300µs).

Technical Context

The FAN2558S10X uses BiCMOS process technology with a P-channel MOSFET pass element and trimmed bandgap reference to achieve ±1% output accuracy over -40°C to +85°C. Its control loop supports 1µF output capacitors with ESR up to 300mΩ without external compensation.

It integrates fast-enable logic for CDMA applications, active output discharge via internal 100Ω resistor during shutdown, and dual protection: current limit (260–500mA) and thermal shutdown (150°C with 10°C hysteresis). The PG pin asserts low when VOUT falls below 89% of nominal and releases high above 97%.

Key Specifications

Pinout & Package

Package: 5-Lead SOT-23 (JEDEC MO-178AA, 2.9mm × 1.6mm × 1.1mm), RoHS-compliant, lead-free plating.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MCP1700T-1002E/TT and NCP1117ST10T3G, the FAN2558S10X uniquely balances 180mA capability, 100µA ground current, integrated PG, and SOT-23-5 footprint - making it optimal for compact, sequenced, battery-powered 1.0V rails where diagnostic visibility and low standby drain are jointly critical.

Availability

FAN2558S10X is available at Aetrix Electronics and suitable for processor power-up sequencing, cell phone baseband regulation, and PDA application processor biasing requiring stable component supply, long-term lifecycle support, and traceable sourcing.

Supply support for FAN2558S10X 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

onsemi (formerly Fairchild Semiconductor) is a global semiconductor supplier specializing in energy-efficient power management, analog, sensing, and connectivity solutions for automotive, industrial, cloud, and consumer markets.

The FAN2558S10X belongs to the FAN2558 family of low-noise, low-IQ CMOS LDOs engineered specifically for portable electronics requiring precise, sequenced, and low-power 1.0V–3.8V bias rails.

FAQ

What is the maximum input voltage rating for the FAN2558S10X?

The FAN2558S10X has an absolute maximum input voltage (VIN to GND) of 6V per its datasheet Absolute Maximum Ratings table. However, for reliable operation, VIN must remain within the recommended range of 2.7V to 5.5V - especially critical since the device delivers a fixed 1.0V output and requires sufficient headroom for dropout. Exceeding 5.5V risks permanent damage even with short-duration transients.

Does the FAN2558S10X require an external bypass capacitor?

No - the FAN2558S10X does not require an external bypass capacitor. Unlike the FAN2559 (low-noise variant) or adjustable FAN2558ADJ versions, the fixed-output FAN2558S10X lacks a BYP pin and is optimized for standard low-ESR ceramic output capacitance only. Its noise performance (30µV_RMS) is achieved through internal bandgap and error amplifier design, not external bypassing.

How does the power-good (PG) output behave during thermal shutdown?

During thermal shutdown, the FAN2558S10X disables its output but maintains PG assertion: the PG pin remains HIGH as long as VOUT stays ≥97% of 1.0V. Only when VOUT drops below 89% due to overload, input undervoltage, or sustained thermal foldback does PG go LOW. This behavior ensures PG reflects actual output validity - not internal fault state - simplifying system-level fault diagnosis.

Can the FAN2558S10X be used with a 0Ω ESR ceramic capacitor?

Yes - the FAN2558S10X is explicitly characterized for stability with output capacitors having ESR from 0mΩ up to 300mΩ. Its control loop architecture eliminates the need for minimum ESR, allowing direct use of high-quality 1µF X5R/X7R ceramic capacitors (typical ESR < 10mΩ) without series resistance. This simplifies filtering and improves transient response in high-speed digital loads.

Is the FAN2558S10X still recommended for new designs?

No - the FAN2558S10X is marked "DISCONTINUED" and "NOT RECOMMENDED FOR NEW DESIGN" in the official onsemi datasheet (Rev. 2, June 2025). While actively stocked and supported for existing production, designers are advised to consult onsemi's product change notifications and evaluate qualified replacements such as the NCP163AMX100TBG or AP2112K-1.0TRG1 for new projects.