onsemi FAN2108MPX

Overview

FAN2108MPX from ON Semiconductor is a fully integrated synchronous buck regulator delivering up to 8 A output current with 3–24 V input range, 0.8 V to 80% VIN programmable output, and peak efficiency exceeding 95%. It integrates high- and low-side MOSFETs, driver, controller, internal bootstrap diode, and power-good signaling in a single 5 × 6 mm MLP package-designed for point-of-load regulation in space-constrained server and graphics card power rails.

For engineers reviewing the FAN2108MPX datasheet, pinout, applications, or equivalent options, key selection considerations include its programmable 200–600 kHz switching frequency, external compensation for loop stability tuning, pre-bias startup capability, lossless current-mode control, and comprehensive protection suite (OVP/UVP/OTP/current limit).

Technical Context

The FAN2108MPX employs summing current-mode modulation with voltage feedforward, enabling stable operation across its full 3–24 V input range while maintaining tight output regulation. Its lossless current sensing uses the low-side MOSFET's R_DS(ON) for over-current protection and current feedback without external sense resistors.

It features an internal soft-start ramp with fault latch inhibition until T_1.0, programmable current limit via R_ILIM, and dual comparator-based over-current detection (MAX and ADJUST ILIMIT) with temperature-compensated reference tracking of MOSFET conduction losses.

Key Specifications

Pinout & Package

Package: Molded Leadless Package (MLP), 5 × 6 mm, 25-pin with 3 exposed thermal pads (P1, P2, P3). Thermally enhanced layout with dedicated power ground (PGND) and analog ground (AGND) pins minimizes noise coupling and improves thermal dissipation.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MP2315DJ-LF-Z and TPS54821RHLR, the FAN2108MPX uniquely combines 8 A capability, 3–24 V input, internal bootstrap diode, and full external compensation in a thermally optimized 5 × 6 mm MLP - making it optimal for high-density, high-efficiency point-of-load designs requiring design flexibility and robust fault handling.

Availability

FAN2108MPX is available at Aetrix Electronics and suitable for server power delivery, GPU point-of-load regulation, and battery-powered test equipment requiring stable component supply, long-term lifecycle support, and traceable sourcing.

Supply support for FAN2108MPX 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

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

The FAN2108MPX belongs to the TinyBuck™ family of integrated synchronous buck regulators, designed specifically for high-current, space-constrained point-of-load applications in computing infrastructure where thermal performance, efficiency, and protection robustness are critical.

FAQ

What is the maximum output current rating of the FAN2108MPX?

The FAN2108MPX is rated for continuous output current of 8 A under recommended operating conditions (T_A ≤ +85°C, proper PCB thermal design). Peak current capability reaches 12–18 A depending on R_ILIM configuration and thermal margin, with over-current protection triggering after 16 consecutive current-limit cycles.

Does the FAN2108MPX support pre-bias startup?

Yes, the FAN2108MPX supports pre-bias startup: it prevents output discharge during startup into a pre-charged rail by inhibiting low-side MOSFET conduction until the internal soft-start ramp reaches ~95% of V_REF (~0.76 V), ensuring controlled inductor current ramp-up without "ratcheting."

What package type and thermal characteristics does the FAN2108MPX use?

The FAN2108MPX uses a 5 × 6 mm Molded Leadless Package (MLP) with 25 pins and three exposed thermal pads (P1, P2, P3). Its thermal resistance is θ_J-PCB = 35 °C/W on a four-layer 2-oz copper PCB, and θ_JC ranges from 4 °C/W (P1, Q2) to 7 °C/W (P2, Q1), enabling high-power dissipation in compact layouts.

How is the switching frequency programmed on the FAN2108MPX?

The switching frequency of the FAN2108MPX is set by an external resistor R_T connected between the R(T) pin (Pin 18) and AGND. The relationship is R_T (kΩ) = 135 / (f − 65), where f is in kHz - e.g., 50 kΩ yields ~300 kHz, and 24 kΩ yields ~600 kHz. Leaving R_T open prevents startup.

What protections are built into the FAN2108MPX?

The FAN2108MPX includes over-voltage protection (110–121% V_OUT), under-voltage shutdown (68–78% V_OUT), over-temperature shutdown (155°C), programmable current limit (12–18 A), input UVLO (4.1–4.5 V on VCC), and fault-latched power-good signaling - all active during normal operation and soft-start.