PAM2846
Integrated 6 String LED Boost Type Driver
Features
n
Six Constant-Current Output Channels
n
Parallel Channels Allow Higher Current
per LED String
n
Maximum 40V Continuous Voltage Output
Limit for Each Channel
n
Self-adaptive Vout to Fit Different LED Number
n
Adjustable Constant LED Current
n
Drives 10 or more LEDs Each String as Long
as the String Voltage Less Than 40V
n
Internal 2.5A Power MOSFET
n
Low 400mV Feedback Voltage at Full
Current Improves Efficiency
n
Allows Digital PWM and Analog Dimming
n
Wide (100:1) PWM Dimming Range without
Color Shift
n
Independent Dimming and Shutdown
Control of the LED Driver
n
±1% Typical Current Matching between Strings
n
Open LED Protection: Adjustable Clamp
Voltage
n
Short LED Protection
n
3 Frequencies Selection: 1.6MHz/1MHz/500kHz
n
Wide Input Voltage Range: 4.8V to 28V
n
Over Temperature Protection
n
Available in 24-pin 4mmx4mm QFN Package
n
Pb-free Package
Description
The PAM2846 is a high-efficiency boost type LED
driver. It is designed for large LCD panel that
employs an array of LEDs as back light source.
The PAM2846 employs a current-mode step-up
converter that drives six parallel strings of LEDs
connected in multiple series. This built-in string-
current-control circuit achieves ±1% typical
current matching between strings, which ensures
even brightness for all LEDs. The device is able to
adapt to different numbers of LEDs in each string
or different forward voltage for different types of
LEDs and keep the string current constant.
Separate feedback loops limit the output voltage if
one or more LEDs open or short. The limit voltage
of over voltage protection is adjustable by
changing the feedback resistor ratio. The
PAM2846 has features cycle-by-cycle current
limit to provide consistent operation and soft-start
capability. A thermal-shutdown circuit provides
another level of protection.
The PAM2846 has a wide +4.8V to +28V input-
voltage range and provides adjustable full-scale
LED current. The switching frequency of this
device can be selected among 500kHz, 1MHz and
1.6MHz according to the application
requirements.
Applications
n
White or RGB Backlighting for LCD
TV, LCD Monitor, Notebook, Handy
Terminals, and Avionics Displays Panels
n
LED Lighting Devices
Typical Application
VIN: 4.8V to 28V
22 μ H
3A/40V
L
SW
SW
SW
OVP
R
2
VIN
ENA
PWMD
Fsel
PWMD
Fsel
R
1
300k
Total 10
LEDs
per
string
PAM2846
VC
Vcc-5V
Vcc-driver
0-10k
1μ
1μ
10K
100nF
GND
LED1
LED2
LED3
LED4
LED5
LED6
9.2k
Iset
PGND PGND PGND
Power Analog Microelectronics
,
Inc
www.poweranalog.com
07/2008 Rev 1.2
1
PAM [ POWER ANALOG MICOELECTRONICS ]
