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MAX8831：High Efficiency White LED Step-Up Converter with I²C Interface in 2mm x 2mm WLP

Easily Drives Five Banks of 9 LEDs with Over 90% Efficiency Using an I²C Interface in a 2mm x 2mm WLP

The MAX8831 integrates a 60mA, 28V PWM DC-DC step-up converter with five low-dropout LED current regulators for display and keypad backlighting in cell phones, PDAs, and other portable devices. The IC provides up to 90% efficiency over the entire input voltage range of 2.7V to 5.5V. The step-up converter operates at a fixed 2MHz switching frequency, enabling the use of very small external components to achieve a compact circuit area. For improved efficiency, the step-up converter automatically transitions to pulse-skipping mode at light loads. Each of the five current regulators accommodates up to 9 series LEDs (depending on LED string forward voltage), and is independently programmed using an I²C interface. Two of the current regulators (LED1, LED2) are intended to support display backlight functions and are programmable up to 25mA using a 128-step logarithmic dimming scheme. The other three regulators (LED3, LED4, LED5) are suitable for keyboard backlight functions or for driving signal indicators, and are programmable up to 5mA using a 32-step logarithmic dimming scheme. The low-current regulators (LED3, LED4, LED5) can be operated from the step-up converter or from a separate low-voltage source. The I²C interface controls all operational aspects of the current regulators, including: on/off state, LED current, ramp-up/ramp-down timers, and blink rate timers (LED3, LED4, LED5). The MAX8831 write/read addresses are factory programmed at 0x9A/0x9B (contact the factory for other address options). The MAX8831 features open/short LED fault detection, output overvoltage protection, thermal shutdown, and open-circuit Schottky diode detection, with the status of each fault monitored continually for readback through the I²C interface. The MAX8831 is available in a tiny 2mm x 2mm, 16-bump WLP package.

Key Features Highly Integrated 28V Step-Up DC-DC Converter with Programmable Functionality Lowers System Cost Integrated NMOS Power Switch Two 25mA Regulators for Display Backlighting I2C-Programmable 50µA to 25.25mA Output Current 128-Step Logarithmic Dimming Individually Programmable Ramp (Up/Down) Timers Low Dropout (200mV max) Three 5mA Current Regulators for Keypad Lighting with I2C-Programmable 50µA to 5.0mA Output Current 32-Step Logarithmic Dimming Individually Programmable Ramp (Up/Down) Timers Individual Blink Rate and Duty Cycle Timers Low Dropout (150mV max) I2C Programmable Compatible with 1.8V Logic Protection Features Increase Reliability Open/Short LED and Open-Circuit Diode Detection Thermal-Shutdown and Output Overvoltage Protection High Efficiency and Low Shutdown Current Extend Battery Life > 90% Efficiency Pulse Skipping for Improved Light-Load Efficiency Ultra-Low 0.1µA Shutdown Current Small Solution Size Saves Board Space Tiny 2mm x 2mm, 16-Bump WLP Package 2MHz Switching Frequency Allows Use of Tiny External Components

MAX8831: Typical Operating Circuit Applications/Uses Cell Phones PDAs Smartphones

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Design kits & evaluation modules

• MAX8831EVKIT

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