Power Electronics

White LED Charge Pump

Maxim Integrated Products’ new MAX1574 is high-efficiency LED charge pump that requires only one transfer capacitor for simplest implementation. Packaged in a 3-mm × 3-mm TDFN, this device is the simplest and smallest solution for cell phones and other handheld devices.

The charge pump drives up to three parallel white LEDs with a regulated, constant current for uniform intensity. By utilizing adaptive 1×/2× modes and low-dropout current regulators, it achieves up to 92% peak efficiency or 83% average efficiency over the full 1-cell Lithium-ion (Li+) battery input-voltage range. It provides 0.6% current matching for uniform backlighting of color LCD displays.

The MAX1574's high output current (up to 180mA) permits use in camera strobes/flashes, movie lights, and keyboard backlight applications. It features a single-wire, serial-pulse interface for dimming down to 5% of peak, soft-start to limit inrush current, overvoltage protection, thermal shutdown, and complete input-to-output disconnect during shutdown (0.1 µA shutdown current). The input voltage range is 2.7 V to 5.5 V. The 1-MHz fixed-frequency switching allows for tiny external components and the regulation scheme is optimized to ensure low EMI and low input ripple.

The MAX1574 is screened for the extended-industrial temperature range (-40°C to +85°C).

For more information, visit www.maxim-ic.com.

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