FAN5606 Datasheet, PDF (1/9 Pages) Fairchild Semiconductor – Serial LED Driver with Current-Regulated, Step-Up DC/DC Converter

www.fairchildsemi.com
FAN5606
Serial LED Driver with Current-Regulated, Step-Up
DC/DC Converter
Features
• Drives Up to Six LEDs in Series
• Pulse Skip PWM Mode of Operation of the Boost Circuit
• Up to 90% Peak Efficiency
• No External Schottky Diode Required
• Up to 25mA Output
• Built-in DAC for Digital Brightness Control
• LED’s Current Can be Duty-Cycle-Modulated
• Digital, Analog, and PWM Brightness Control
• 2.7V to 5.5V Input Voltage Range
• 0.5MHz Operating Frequency (8MHz internal clock)
• Soft Start
• Low Shutdown Current: I_CC < 1µA
• LED Short Circuit Protection
• Minimal External Components Needed
• Available in an 8-lead MLP Package
Applications
• Cell Phones
• Handheld Computers
• PDAs, DSCs, MP3 Players
• Keyboard Backlights
• LED Display
Description
The FAN5606 LED driver generates regulated output cur-
rents from a battery with input voltage varying between 2.7V
to 5V. An internal NMOS switch drives an external inductor,
and a Schottky diode delivers the inductor’s stored energy to
the load. Soft start circuitry prevents excessive current drawn
from the supply during power on. Any number of LEDs can
be connected in series as long as the summed forward volt-
ages do not lead to exceeding the specified operating output
voltage range.
In the FAN5606 device, the internal two-bit D/A converters
provide programmability of the output channel current.
Analog programming of the output current is also possible
in the FAN5606. To do this, ground the “B” pin and connect
a resistor between the “A” pin and a fixed supply voltage.
The output current can then be programmed to any desired
value within its specified range. The analog version uses a
single external resistor to set the current, and to turn the
device ON and OFF. The device is available in an 8-lead
MLP package.
Typical Applications
Analog Brightness Control
2.7V to 5.5V L = 6.8µH
C_IN
V_External
R
IND V_OUT GINND
V_IN
CAT
A
B
4.7µF
Digital Brightness Control
V_OUT
2.7V to 5.5V L = 6.8µH
IND
C_IN
V_IN
A
DAC Inputs
GINND
CAT
B
4.7µF
V_OUT
REV. 1.0.3 1/7/05