onsemi FAN2306MPX

Overview

FAN2306MPX from onsemi (formerly Fairchild) is a 6 A synchronous buck regulator with constant-on-time control architecture, operating from 4.5 V to 18 V input and delivering adjustable output voltage from 0.6 V to 5.5 V. It features PFM mode for light-load efficiency, programmable switching frequency (200 kHz–1.5 MHz), ±1% reference accuracy over temperature, and integrated thermal shutdown - deployed in server VRMs and notebook NVDC power rails.

For engineers reviewing the FAN2306MPX datasheet, pinout, applications, or equivalent options, key selection considerations include ultrasonic-mode operation (minimum frequency clamp enabled), 34-pin PQFN package thermal performance (θ_JA = 35°C/W), valley-current limiting via ILIM resistor programming, and PGOOD open-drain fault signaling.

Technical Context

The FAN2306MPX implements constant-on-time modulation with VIN feed-forward to maintain stable switching frequency in CCM while enabling seamless transition into PFM at light loads. Its minimum off-time (320 ns) ensures reliable low-side current sensing and prevents multiple pulsing during transients.

Unlike the FAN2306M variant, the FAN2306MPX includes an audible-frequency clamp (18.2–32.7 kHz min) to suppress ultrasonic noise - achieved by forcing LS turn-on when frequency drops below threshold. Protection logic integrates dual-level OVP (+11% and +22% FB trip), UVP (−11% VREF), valley-current limiting, and thermal shutdown with 15°C hysteresis.

Key Specifications

Pinout & Package

Package: 34-lead PQFN, 5.5 mm × 5.0 mm, exposed thermal pad - optimized for high-current DC/DC conversion with low θ_JA (35°C/W) on 4-layer PCBs.

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 TPS546B24RVFR, the FAN2306MPX delivers superior light-load efficiency via ultrasonic PFM and offers analog flexibility (programmable frequency, soft-start, current limit) without digital overhead - ideal for analog-centric, thermally demanding embedded power rails.

Availability

FAN2306MPX is available at Aetrix Electronics and suitable for server VRMs, notebook NVDC power stages, and telecom base station DC/DC converters requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for FAN2306MPX 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 focused on energy-efficient power management, analog, and sensor solutions for automotive, industrial, and cloud infrastructure markets.

The FAN2306MPX belongs to onsemi's high-current synchronous buck regulator product line, designed specifically for high-efficiency, low-noise point-of-load conversion in computing and communications equipment.

FAQ

What is the key functional difference between FAN2306MPX and FAN2306MMPX?

The FAN2306MPX includes an ultrasonic-mode frequency clamp (18.2–32.7 kHz minimum) to suppress audible noise during light-load PFM operation, whereas the FAN2306MMPX omits this clamp to maximize efficiency at extremely low loads. Both share identical pinout, package, and 6 A current rating, but only FAN2306MPX guarantees operation above the human-audible range under all conditions. This makes FAN2306MPX preferred for consumer-facing devices like notebooks and game consoles where acoustic noise matters.

Does FAN2306MPX require an external bootstrap diode?

No, the FAN2306MPX integrates an internal boot diode connected between PVCC and BOOT, eliminating the need for an external diode. This reduces BOM count and improves reliability by removing a common failure point in high-frequency buck designs. The internal diode has a typical forward voltage of 0.6 V at 10 mA and reverse leakage under 1000 µA at 5 V - sufficient for standard 1.2 µH inductor applications with 12 V input.

How is output voltage programmed on FAN2306MPX?

Output voltage on FAN2306MPX is set using a resistive divider from VOUT to AGND, with the midpoint connected to the FB pin. The internal reference is 596 mV (±1% over temperature), so VOUT = 0.596 V × (1 + R1/R2). For example, a 54.9 kΩ top resistor and 1.5 kΩ bottom resistor yields 1.2 V. The FB pin bias current is ±100 nA, minimizing divider error - enabling accurate regulation down to 0.6 V with appropriate resistor selection.

What thermal performance can be expected from FAN2306MPX in a standard 4-layer PCB layout?

On a 4-layer PCB (1 oz copper, 7 cm × 7 cm), the FAN2306MPX achieves θ_JA = 35°C/W and ψ_JPCB = 2.3°C/W. At 6 A load with 12 V input and 1.2 V output, typical power dissipation is ~1.2 W - resulting in ~42°C junction-to-ambient rise above ambient. With 25°C ambient, junction temperature reaches ~67°C, well below the 125°C max operating limit. Thermal pad soldering and 6+ vias to inner ground planes are essential to realize this performance.

Can FAN2306MPX start up safely when the output is pre-biased?

Yes, FAN2306MPX supports pre-bias startup: when EN is asserted with VOUT already charged, the low-side MOSFET remains disabled until the first PWM edge, preventing reverse current flow and output discharge. The controller forces PFM mode during soft-start to keep inductor current positive, ensuring monotonic ramp-up even with 1.2 V pre-bias. This behavior is confirmed in Figure 20 of the datasheet and eliminates need for external OR-ing FETs in hot-swap applications.