1.2A White LED Regulating Charge Pump for Camera Flashes and Movie Lights

The MAX1577Y/MAX1577Z charge pumps drive white LEDs, including camera strobes, with regulated current up to 1.2A (guaranteed to 800mA). The very low openloop output resistance allows high flash brightness, even from a low battery input voltage. The adaptive 1x/2x regulating charge-pump operation provides high efficiency (up to 92%) while in movie mode or backlighting. Fast (1MHz) switching allows the use of tiny external components.

The MAX1577Y/MAX1577Z use an external resistor to set the full-scale LED current. Two enable inputs (EN1 and EN2) provide simple on/off control and LED current of 20%, 33%, or 100% full scale. If there is less than 24mV across the external resistor, the output voltage is regulated. The MAX1577Z has fixed 5.1V output-voltage regulation, while the MAX1577Y has logic-controlled output voltage of 3.4V, 4.6V, or 5.1V for backlighting, keyboard, and RGB applications.

The MAX1577Y/MAX1577Z are available in an 8-pin, 3mm x 3mm TDFN package (0.8mm max height).

Applications

* Camera Phones, Cell Phones, and Smartphones * LCD Backlights * PDAs, Digital Cameras, and Camcorders * White LED Flashes, Strobes, and Movie Lights

* Up to 1.2A Output Drive Capability (800mA Guaranteed)

* Up to 92% PLED / PBATT Efficiency for Movie Mode

* Flexible Brightness Control

* Two-Bit Logic for 100%, 33%, 20%, and Off

* PWM for 20% to 100%

* 3% Current Regulation Over Line and Temperature

* Current or Voltage Regulation for Flash and Backlighting (MAX1577Y)

* Current Regulation for Flash (MAX1577Z)

* Low Ripple and EMI

* 2.7V to 5.5V Supply Voltage Range

* Soft-Start Limits Inrush Current

* Output-Voltage Regulation Mode

* Thermal-Shutdown Protection

* 8-Pin 3mm x 3mm TDFN Package