
Maxim Integrated
General Description
The MAX8822 drives up to four white light-emitting diodes (LEDs) with regulated constant current for display backlighting in cell phones, digital cameras, PDAs, and other handheld devices. By utilizing a proprietary negative 0.5x inverting charge pump and innovative independent low-dropout (LDO) adaptive current regulators, very high efficiency is achieved over the full 1-cell Li+ battery voltage range, even with large LED VF mismatch. The 1MHz fixed-frequency switching allows for tiny external components. The regulation scheme is optimized to ensure low EMI and low input ripple. Two 200mA, low-noise, high power-supply-rejection-ratio (PSRR) LDOs with programmable output voltages are included on-chip to provide power to camera modules or other devices.
FEATUREs
♦ High-Efficiency Charge Pump for Up to Four White LEDs
Independent Adaptive Voltage Supply for Each LED
24mA to 0.1mA Dimming Range
1% (typ) Current Accuracy and 0.3% Current Matching
Low 65µA (typ) Quiescent Current
♦ Dual 200mA Low-Noise, High PSRR LDOs
16 Different Output Voltage Combinations Up to 3.3V
High 60dB PSRR at 10kHz
♦ Flexible Single-Wire Control for Dimming and LDO Output Voltage
♦ Low 0.5µA (typ) Shutdown Mode
♦ Soft-Start Limits Inrush Current
♦ Thermal Shutdown and Open- and Short-Circuit Protection
♦ Tiny 16-Pin, 3mm x 3mm Thin QFN Package
(0.8mm max Height) with Exposed Paddle
APPLICATIONs
White LED Backlighting
Cell Phones and Smartphones