March 2011

© 2009 Fairchild Semiconductor Corporation

www.fairchildsemi.com

FAN5354 • Rev. 1.0.5

FAN5354

3MHz, 3A Synchronous Buck Regulator

Features

3MHz Fixed-Frequency Operation

Best-in-Class Load Transient

3A Output Current Capability

2.7V to 5.5V Input Voltage Range

PFM Mode for High Efficiency in Light Load (Forced PWM

Available on MODE Pin)

Minimum PFM Frequency Avoids Audible Noise

270 A Typical Quiescent Current in PFM Mode

External Frequency Synchronization

Low Ripple Light-Load PFM Mode with Forced

PWM Control

Power Good Output

Internal Soft-Start

Input Under-Voltage Lockout (UVLO)

Thermal Shutdown and Overload Protection

12-Lead 3x3.5mm MLP

Applications

Set-Top Box

Hard Disk Drive

Communications Cards

DSP Power

Description

The FAN5354 is a step-down switching voltage regulator that

delivers an adjustable output from an input voltage supply of

2.7V

to

5.5V.

Using

a

proprietary

architecture

with

synchronous rectification, the FAN5354 is capable of

delivering 3A at over 85% efficiency, while maintaining a

very high efficiency of over 80% at load currents as low as

2mA. The regulator operates at a nominal fixed frequency of

3MHz, which reduces the value of the external components

to 470nH for the output inductor and 10 F for the output

capacitor. Additional output capacitance can be added to

improve regulation during load transients without affecting

stability and inductance up to 1.2 H may be used with

additional output capacitance.

At moderate and light loads, pulse frequency modulation

(PFM) is used to operate the device in power-save mode

with a typical quiescent current of 270 A. Even with such a

low quiescent current, the part exhibits excellent transient

response during large load swings. At higher loads, the

system automatically switches to fixed-frequency control,

operating at 3MHz. In shutdown mode, the supply current

drops below 1 A, reducing power consumption. PFM mode

can be disabled if constant frequency is desired. To avoid

audible noise, the regulator limits its minimum PFM

frequency. The FAN5354 is available in 12-lead 3x3.5mm

MLP package.

Figure 1. Typical Application

Ordering Information

Part Number

Temperature Range

Package

Packing Method

FAN5354MPX

-40 to 85°C

MLP-12, 3x3.5mm

Tape and Reel