onsemi FAN53611AUC115X

Overview

FAN53611AUC115X from onsemi is a 6 MHz, 1 A synchronous buck regulator in WLCSP-6 package delivering a fixed 1.150 V output from 2.3–5.5 V input. It features 24 µA quiescent current in PFM mode, internal soft-start, forced PWM operation, and active output discharge. It targets power management in space-constrained portable electronics requiring high efficiency at light loads.

For engineers reviewing the FAN53611AUC115X datasheet, pinout, applications, or equivalent options, key selection criteria include its 1.150 V fixed output, 1 A capability, 6 MHz switching frequency enabling ultra-small 470 nH inductors and 4.7 µF capacitors, and support for external clock synchronization via MODE pin.

Technical Context

The FAN53611AUC115X employs a proprietary non-linear fixed-frequency PWM modulator with seamless auto-transition between PWM and PFM modes. Its control loop is independent of output capacitor ESR, enabling stable operation with low-ESR ceramic capacitors.

It integrates PMOS and NMOS synchronous rectifiers with 175 mΩ and 165 mΩ typical R_DS(on), respectively, and delivers peak efficiency of 92% while sustaining >80% efficiency down to 1 mA load. Thermal shutdown activates at 150°C with 15°C hysteresis, and UVLO triggers at 2.27 V (rising) with 200 mV hysteresis.

Key Specifications

Pinout & Package

Package: Wafer-Level Chip-Scale Package (WLCSP-6), 0.4 mm pitch, 1.16 mm × 0.86 mm body, 547–625 µm height. Bumps face down in standard mounting orientation.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TPS62260DRVR and RTQ2132BGQW, the FAN53611AUC115X uniquely combines 1 A capability, 6 MHz frequency, factory-trimmed 1.150 V, and active discharge in a 0.4 mm pitch WLCSP-making it optimal for compact, battery-powered SoC rails demanding dynamic efficiency and precise sequencing.

Availability

FAN53611AUC115X is available at Aetrix Electronics and suitable for mobile baseband power, Wi-Fi/Bluetooth SoC core supply, tablet application processor rails, and ultra-mobile PC DDR memory I/O supply requiring stable component supply across high-volume production cycles.

Supply support for FAN53611AUC115X 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 ON Semiconductor) is a global semiconductor supplier specializing in energy-efficient power management, analog, sensor, and connectivity solutions for automotive, industrial, cloud, and consumer markets.

The FAN53611AUC115X belongs to the FAN536xx family of high-frequency synchronous buck regulators designed specifically for space-constrained portable electronics requiring ultra-small passives, fast transient response, and multi-mode efficiency optimization.

FAQ

What is the output voltage tolerance of the FAN53611AUC115X over temperature and load?

The FAN53611AUC115X delivers a nominal 1.150 V output with ±4.6% accuracy (1.104 V to 1.196 V) across full load (0–1 A) and operating temperature (–40°C to +85°C). In PWM mode only, tolerance tightens to ±4.3% (1.110–1.190 V). This is verified per the Electrical Characteristics table in the official datasheet Rev. 2, December 2017.

Does the FAN53611AUC115X support external clock synchronization, and what is the valid input frequency range on the MODE pin?

Yes, the FAN53611AUC115X supports external clock synchronization via the MODE pin. When driven with a square wave between 1.3 MHz and 1.7 MHz, the device locks its switching frequency to four times the input (5.2–6.8 MHz). The MODE pin includes Schmitt-trigger buffering to tolerate slow edges, and asymmetric duty cycles are acceptable if high/low pulses exceed 100 ns.

What is the purpose of the active output discharge feature in the FAN53611AUC115X, and how is it controlled?

The active output discharge feature in the FAN53611AUC115X provides a 230 Ω internal path from FB to GND when EN is low, rapidly collapsing VOUT during shutdown. This ensures clean power-down sequencing for downstream logic and eliminates floating rail conditions. Discharge is enabled by default on all "AUC" variants like FAN53611AUC115X and requires no external components.

Can the FAN53611AUC115X operate with input voltages below 2.3 V, and what happens if VIN drops below UVLO threshold?

No-the FAN53611AUC115X has a guaranteed operating minimum input voltage of 2.3 V. Its under-voltage lockout (UVLO) activates at 2.27 V (rising) with 200 mV hysteresis, disabling regulation until VIN rises above ~2.47 V. Below UVLO, the IC draws <1 µA and holds SW low; no regulated output is delivered, preventing unstable operation during brown-out conditions.

What are the recommended external components for the FAN53611AUC115X, and why is the 470 nH inductor critical?

The recommended components are a 470 nH shielded inductor (e.g., Murata LQM21PNR47MC0), 2.2 µF X5R 0402 input capacitor, and 4.7 µF X5R 0402 output capacitor. The 470 nH value is critical because the 6 MHz switching frequency and internal control loop are optimized for this inductance-deviations shift the PFM/PWM transition point, affect ripple, and may degrade transient response or stability.