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.