1 Features
1• Drives Three Parallel High-Voltage LED Strings
for Display and Keypad Lighting
• High-Voltage Strings Capable of up to 40-V
Output Voltage and up to 90% Efficiency
• Up to 30-mA per Current Sink (Both Backlight and
Indicator)
• 11-Bit High-Voltage LED Dimming
• PWM Input for Content Adjustable Brightness
Control (CABC)
• Integrated 1-A/40-V MOSFET
• Adaptive Boost Output to LED Voltages
• Six Low-Voltage Current Sinks for Indicator LEDs
• Integrated Charge Pump for Improved Efficiency
and V IN Operating Range
• Internal Pattern Generation Engine for Each
Indicator LED
• Fully Configurable LED Grouping and Control
• Four Programmable Overvoltage Protection
Thresholds (16 V, 24 V, 32 V, and 40 V)
• Programmable 500-kHz and 1-MHz Switching
Frequency
• Overcurrent Protection
• Thermal Shutdown Protection
• 27 mm2 Total Solution Size

2 Applications
• Power Source for Smart Phone Illumination
• Display, Keypad and Indicator Illumination
• RGB Indicator Driver

3 Description
The LM3633 11-bit LED driver provides high-
performance backlight dimming for 1, 2, or 3 parallel
high-voltage LED strings while delivering up to 90%
efficiency. The boost converter with integrated 1-A,
40-V MOSFET automatically adjusts to LED forward
voltage to minimize headroom voltage and effectively
improve LED efficiency.
The LM3633 is a complete power source for
backlight, keypad, and indicator LEDs in smartphone
handsets. The high-voltage inductive boost converter
provides the power for three parallel LED strings (HVLED1, HVLED2 and HVLED3). The integrated
charge pump provides the bias for the six low-voltage
indicator LEDs (LVLED1-LVLED6). All low-voltage
current sinks can have a programmable pattern
modulated onto their output current for a wide variety
of blinking patterns.
An additional feature is a Pulse Width Modulation
(PWM) control input for content adjustable backlight
control, which can be used to control any high-
voltage current sink.
The LM3633 is fully programmable via an I2C-
compatible interface. The device operates over a 2.7-
V to 5.5-V input voltage range and a −40°C to 85°C
temperature range.