FAN5308 Datasheet, PDF (1/11 Pages) Fairchild Semiconductor – 800mA High-Efficiency Step-Down DC-DC Converter

April 2005
FAN5308
800mA High-Efficiency Step-Down DC-DC Converter
Features
■ 96% Efficiency, Synchronous Operation
■ Adjustable Output Voltage Options from 0.8V to V_IN
■ 2.5V to 5.5V Input Voltage Range
■ Up to 800mA Output Current
■ Fixed Frequency 1.3MHz PWM Operation
■ High Efficiency Power Save Mode
■ 100% Duty Cycle Low Dropout Operation
■ Soft Start
■ Output Over-Voltage Protection
■ Dynamic Output Voltage Positioning
■ 25µA Quiescent Current
■ Thermal Shutdown and Short Circuit Protection
■ Pb-Free 3x3mm 6-Lead MLP Package
Applications
■ Pocket PCs, PDAs
■ Cell Phones
■ Battery-Powered Portable Devices
■ Digital Cameras
■ Hard Disk Drives
■ Set-Top-Boxes
■ Point-of-Load Power
■ Notebook Computers
■ Communications Equipment
Description
Designed for use in battery-powered applications, the FAN5308
is a high-efficiency, low-noise synchronous PWM current mode
and Pulse Skip (Power Save) mode DC-DC converter. It can
provide up to 800mA of output current over a wide input range
from 2.5V to 5.5V. The output voltage can be externally adjusted
over a wide range of 0.8V to 5.5V by means of an external volt-
age divider.
At moderate and light loads, pulse skipping modulation is used.
Dynamic voltage positioning is applied, and the output voltage is
shifted 0.8% above nominal value for increased headroom dur-
ing load transients. At higher loads the system automatically
switches over to current mode PWM control, operating at 1.3
MHz. A current mode control loop with fast transient response
ensures excellent line and load regulation. To achieve high effi-
ciency and ensure long battery life, the quiescent current is
reduced to 25µA in Power Save mode, and the supply current
drops below 1µA in shut-down mode. The FAN5308 is available
in a 3x3mm 6-lead MLP package.
Typical Application
C_IN
10µF
V_IN
1
PGND
2
EN
3
P1
(AGND)
SW
6
3.3µH
5 NC
R1
FB
4
5KΩ
R2 10KΩ
V_OUT
1.2V (800mA)
C_OUT
2 x 10µF
Figure 1. Typical Application
FAN5308 Rev. 1.0.1
1
©2005 Fairchild Semiconductor Corporation
www.fairchildsemi.com