High Efficiency White LED Step-Up Converter with I²C Interface in 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.

Applications

* Cell Phones * PDAs * Smartphones

* 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