June 2007
FAN5308
tm
800mA High-Efficiency Step-Down DC-DC Converter
Features
■ 96% efficiency, synchronous operation
■ Adjustable output voltage options from 0.8V to VIN
■ 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 an input range from 2.5V to 5.5V. The output
voltage can be externally adjusted over a range of 0.8V
to 5.5V by means of an external voltage 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 during load transients. At higher
loads, the system automatically switches over to current
mode PWM control, operating at 1.3MHz. 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.
Ordering Information
Product Number
FAN5308
Output Voltage
Adjustable
Package Type
3x3mm 6-Lead MLP
Order Code
FAN5308MPX
Typical Application
CIN
10μF
VIN
1
PGND
2
EN
3
P1
(AGND)
SW
6
3.3μH
5 NC
R1
FB
4
5KΩ
R2 10KΩ
VOUT
1.2V (800mA)
COUT
2 x 10μF
© 2005 Fairchild Semiconductor Corporation
FAN5308 Rev. 1.0.2
Figure 1. Typical Application
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