Four-String White LED Driver
Data Sheet
ADD5205
Rev. 0
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FEATURES
White LED driver based on inductive boost converter
Input voltage range: 2.8 V to 18 V
Internal compensation
1 MHz fixed operating frequency
28 V fixed overvoltage protection
Built-in soft start for boost converter
Drives up to 4 LED current sources
LED current adjustable up to 25 mA for each channel
DC current level brightness control with PWM input
LED open fault protection
General
Thermal shutdown
Undervoltage lockout
12-lead, 3 mm × 3 mm × 0.75 mm LFCSP package
APPLICATIONS
Smart PCs, PMPs, tablet PCs, UMPCs, and notebooks
FUNCTIONAL BLOCK DIAGRAM
STEP-UP SWITCHING REGULATOR
4-CHANNEL CURRENT SOURCES
BRIGHTNESS CONTROL LOGIC
UNDERVOLTAGE LOCKOUT
SOFT START
THERMAL PROTECTION
OVERVOLTAGE PROTECTION
AUTODISABLE FOR LED OPEN
09858-001
Figure 1.
GENERAL DESCRIPTION
The ADD5205 is a white LED driver for backlight applications
based on high efficiency, current mode, step-up converter
technology. It is designed with a 0.3 Ω internal switch and 1 MHz
fixed operating frequency. The ADD5205 contains four regulated
constant current sources for uniform brightness intensity. Each
current source is capable of driving up to 25 mA.
The ADD5205 has four parallel strings of multiple series connected
LEDs with ±2% current matching. The device provides adjustable
current sources that drive up to 25 mA using an external resistor.
The LED current can be controlled by a PWM signal input on
the PWM pin. An internal circuit translates the PWM signal to
an analog signal with an external capacitor and linearly controls
the LED current.
The ADD5205 has multiple safety protection features to prevent
any damage during fault conditions. If one or more LEDs are open,
the device disables the faulty current regulator automatically.
The internal soft start prevents inrush current during startup. A
thermal shutdown protection feature prevents thermal damage.
The ADD5205 is available in a low profile, thermally enhanced
3 mm × 3 mm × 0.75 mm, 12-lead lead frame chip scale package
(LFCSP) and is specified over the temperature range of −25°C
to +85°C.
