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Four-String, White LED Driver
for LCD Backlight Applications
Data Sheet
ADD5211
Rev. 0 Document Feedback
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FEATURES
White LED driver based on an inductive boost controller
Wide input voltage range: 4.5 V to 40 V
Adaptive output voltage to minimize power dissipation
Adjustable operating frequency: 200 kHz to 1.2 MHz
Programmable UVLO
Programmable soft start time for boost converter
Programmable external MOSFET switching rising/falling time
Drives up to 4 LED current sinks with internal MOSFETs
Brightness control with PWM input
Adjustable LED current: 40 mA to 200 mA
Headroom control to maximize efficiency
LED dimming frequency: up to 25 kHz
PWM dimming at 300 Hz: 1000:1
Open-drain fault indicator
LED open and LED short fault protection
Thermal shutdown
Undervoltage lockout (UVLO)
24-lead, 4 mm × 4 mm LFCSP
APPLICATIONS
LCD monitor and TV LED backlights
Industrial lighting
GENERAL DESCRIPTION
The ADD5211 is a four-string, white LED driver for backlight
applications based on high efficiency, current mode, step-up
converter technology. The boost controller drives an external
MOSFET switch for step-up regulation from an input voltage
of 4.5 V to 40 V and a pin adjustable operating frequency from
200 kHz to 1.2 MHz. An adjustable UVLO function is implemented
to reduce input current during power-off.
The ADD5211 provides four regulated current sinks for uniform
brightness intensity. Each current sink can be driven from 40 mA
to 200 mA; the LED driving current is pin adjustable using an
external resistor. With an input PWM interface, the ADD5211
drives up to four parallel strings of multiple series connected LEDs.
Additional features include LED short protection, LED open
protection, boost output short protection, overvoltage protection,
cycle-by-cycle current limit, and thermal shutdown for both the
IC and the LED array. An open-drain fault output is also included.
A programmable soft start is implemented to reduce inrush
current during startup.
APPLICATION CIRCUIT
10555-001
VINUVLO
GATE_P GATE_N
+
OFF ON
EN
ISET
LSD
VDD
FAULT
PWM
VDR
LGND
OVP
FB4
FB3
FB2
FB1
PGND
RAMP
CS
FREQ COMPAGND SS
ADD5211
VIN
Figure 1.
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