Datasheet Analog Devices MAX1573

19-2847; Rev 2; 8/05 White LED 1x/1.5x Charge Pump in
UCSP and Thin QFN
The MAX1573 fractional charge pump drives up to four
white LEDs with regulated constant current for uniform
intensity. By utilizing proprietary adaptive 1x/1.5x
modes and ultra-low-dropout current regulators, it
maintains the highest possible efficiency over the full
1-cell Li+ battery input voltage range. The 1MHz fixedfrequency switching allows for tiny external components and the regulation scheme is optimized to ensure
low EMI and low input ripple.
An external resistor sets the full-scale LED current, while
two digital inputs control on/off and select amongst three
levels of brightness. A pulse-width modulation (PWM)
signal can also be used to modulate LED brightness,
requiring no additional components.
The MAX1573 is available in the tiny chip-scale UCSP™
(4 x 4 grid) and 16-pin thin QFN packages. Features
♦ Proprietary Adaptive 1x/1.5x Modes
♦ High Efficiency (PLEDs/PBATT), Up to 92%
♦ 0.2% LED Current Matching
♦ 28mA/LED Drive Capability
♦ Low Input Ripple and EMI
♦ Eliminates Ballast Resistors
♦ Logic or PWM Dimming Control …