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1.1A charge pumps

Supplier News
article image Bright WLED flashes in camera phones.

MAXIM Integrated Products, represented in Australia by Arrow Electronics , has released the MAX1577Z/MAX1577Y 1x/2x charge pumps. They can drive white LEDs with regulated current up to 1.1A (800mA guaranteed).

Using an adaptive-mode switching technique, the charge pumps provide efficiency of up to 92% in movie mode or backlighting. The open-loop output resistance allows the high WLED flash brightness, even from a low-battery input voltage. The devices require three ceramic capacitors, eliminating the need for a step-up dc/dc converter and low-profile inductor. This ensures that the parts meet the height constraints in clamshell cell phones. 1MHz switching allows the use of tiny external components. The regulation scheme is optimised to ensure low EMI and low input ripple.

The MAX1577Z/MAX1577Y 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. The charge pumps also have soft-start to limit inrush current, thermal-shutdown and complete input-to-output disconnect during shutdown. The input voltage range is 2.7V to 5.5V. The MAX1577Z has fixed 5.1V output overvoltage protection. The MAX1577Y has logic-controlled output current for flash, and 3.4V, 4.6V or 5.1V output voltages for backlight, keyboard and RGB applications.

The MAX1577Z/MAX1577Y are available in an eight-pin, 3mm x 3mm TDFN package, screened for the industrial temperature range from -40ºC to 85ºC.

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