The MAX1576 charge pump drives up to 8 white LEDs
with regulated constant current for uniform intensity.
The main group of LEDs (LED1-LED4) can be driven
up to 30mA per LED for backlighting. The flash group
of LEDs (LED5-LED8) are independently controlled and
can be driven up to 100mA per LED (or 400mA total).
By utilizing adaptive 1x/1.5x/2x charge-pump modes
and very-low-dropout current regulators, the MAX1576
achieves high efficiency over the full 1-cell lithium-battery
voltage range. The 1MHz fixed-frequency switching
allows for tiny external components, and the
regulation scheme is optimized to ensure low EMI and
low input ripple.
The MAX1576 uses two external resistors to set the
main and flash full-scale (100%) LED currents. Four
control pins are used for LED dimming by either serial
control or 2-bit logic per group. ENM1 and ENM2 set
the main LEDs to 10%, 30%, or 100% of full scale.
ENF1 and ENF2 set the flash LEDs to 20%, 40%, or
100% of full scale. In addition, connect either pair of
control pins together for single-wire, serial pulse dimming
control.
The MAX1576 is available in a 24-pin thin QFN, 4mm x
4mm package (0.8mm max height).
Applications
- Camera Phones
- Cell Phones/Smartphones
- LCD Backlights
- LED Camera Flashes
- PDAs, Digital Cameras, and Camcorders
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