FAN5355_10 Datasheet, PDF (1/26 Pages) Fairchild Semiconductor – 1A / 0.8A, 3MHz Digitally Programmable Regulator

May 2010
FAN5355
1A / 0.8A, 3MHz Digitally Programmable Regulator
Features
ƒ 93% Efficiency at 3MHz
ƒ 800mA or 1A Output Current
ƒ I²C™-Compatible Interface up to 3.4Mbps
ƒ 6-bit VOUT Programmable from 0.75V to 1.975V
ƒ 2.7V to 5.5V Input Voltage Range
ƒ 3MHz Fixed-Frequency Operation
ƒ Excellent Load and Line Transient Response
ƒ Small Size, 1μH Inductor Solution
ƒ ±2% PWM DC Voltage Accuracy
ƒ 35ns Minimum On-Time
ƒ High-Efficiency, Low-Ripple, Light-Load PFM
ƒ Smooth Transition between PWM and PFM
ƒ 37μA Operating PFM Quiescent Current
ƒ Pin-Selectable or I²C™ Programmable Output Voltage
ƒ On-the-Fly External Clock Synchronization
ƒ 10-lead MLP (3 x 3mm) or 12-bump CSP Packages
Applications
ƒ Cell Phones, Smart Phones
ƒ 3G, WiFi^®, WiMAX™, and WiBro^® Data Cards
ƒ Netbooks^®, Ultra-Mobile PCs
ƒ SmartReflex™-Compliant Power Supply
ƒ Split Supply DSPs and μP Solutions OMAP™, XSCALE™
ƒ Mobile Graphic Processors (NVIDIA^®, ATI)
ƒ LPDDR2 and Memory Modules
Description
The FAN5355 device is a high-frequency, ultra-fast transient
response, synchronous step-down DC-DC converter
optimized for low-power applications using small, low-cost
inductors and capacitors. The FAN5355 supports up to
800mA or 1A load current.
The device is ideal for mobile phones and similar portable
applications powered by a single-cell Lithium-Ion battery. With
an output-voltage range adjustable via I²C™ interface from
0.75V to 1.975V, the device supports low-voltage DSPs and
processors, core power supplies, and memory modules in
smart phones, PDAs, and handheld computers.
The FAN5355 operates at 3MHz (nominal) fixed switching
frequency using either its internal oscillator or external SYNC
frequency.
During light-load conditions, the regulator includes a PFM
mode to enhance light-load efficiency. The regulator
transitions smoothly between PWM and PFM modes with no
glitches on VOUT. In hardware shutdown, the current
consumption is reduced to less than 200nA.
The serial interface is compatible with Fast/Standard and
High-Speed mode I²C specifications, allowing transfers up to
3.4Mbps. This interface is used for dynamic voltage scaling
with 12.5mV voltage steps for reprogramming the mode of
operation (PFM or Forced PWM), or to disable/enable the
output voltage.
The chip's advanced protection features include short-circuit
protection and current and temperature limits. During a
sustained over-current event, the IC shuts down and restarts
after a delay to reduce average power dissipation into a fault.
During startup, the IC controls the output slew rate to minimize
input current and output overshoot at the end of soft start. The
IC maintains a consistent soft-start ramp, regardless of output
load during startup.
The FAN5355 is available in 10-lead MLP (3x3mm) and
12-bump CSP packages.
I²C is a trademark of Philips Corporation.
Wi-Fi® is a registered trademark of Wi-Fi Alliance Corporation.
WiMax™ is a trademark of WIMAX Forum Corporation.
WiBro® is a registered trademark of Telecommunications Technology Association.
Netbooks® is a registered trademark of Netbooks, Inc.
SmartReflex and OMAP are trademarks of Texas Instruments.
XSCALE is a trademark of Intel Corporation.
NVIDIA is a registered trademark of NVIDIA Corporation.
© 2008 Fairchild Semiconductor Corporation
FAN5355 • Rev. 1.0.6
www.fairchildsemi.com