General Description
The MAX8901A/MAX8901B step-up converters drive from two to six series-connected white LEDs (WLEDs) with constant current to provide uniform WLED intensity for LCD backlighting in cell phones, PDAs, and other handheld devices. The MAX8901_ operate at a fixed 750kHz (typ) switching frequency, allowing for tiny external components, and are optimized for the highest possible efficiency over the full 1-cell Li+/Li-Poly battery range.
These converters use a single input (ON) to enable the IC and to control WLED intensity. The MAX8901A requires a direct PWM input to regulate WLED intensity with the WLED current proportional to the PWM duty cycle. The MAX8901B uses single-wire, serial-pulse dimming that reduces the WLED intensity in 32 linear steps. Full-scale WLED current for serial-pulse
dimming is 24.75mA (MAX8901B, 0.75mA/step).
The MAX8901_ features an internal soft-start to eliminate inrush currents during startup, input overvoltage protection, WLED overvoltage protection, and a shutdown mode with 0.01μA (typ) shutdown current. No WLED current is present in shutdown provided the WLED forward voltage is greater than the input supply voltage. Additional features include undervoltage lockout
(UVLO) and thermal shutdown.
The MAX8901_ are available in tiny 8-pin, 2mm x 2mm TDFN-EP packages (0.8mm max height).

Display Backlight (from 2 to 6 WLEDs)
Cellular Phones
PDAs and Smartphones
MP3 and Portable Media Players
Portable Navigation Devices
Digital Cameras

♦ High Efficiency, Up to 91%
♦ 2.6V to 5.5V Input Voltage Range
♦ Fixed-Frequency Operation
♦ Supplies from 2 to 6 WLEDs with 1% LED Current Accuracy
♦ Flexible Dimming Control Direct PWM Dimming (MAX8901A) 32-Step, 1-Wire Serial Dimming
♦ Input Undervoltage Lockout
♦ Input Overvoltage Lockout
♦ WLED Overvoltage Protection (25V typ)
♦ 0.01μA (typ) Shutdown Current
♦ No WLED Current in Shutdown
♦ Internal Soft-Start and Thermal Shutdown


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