MAXIM Integrated Products, represented by Arrow Electronics , has introduced the MAX1553/MAX1554, the smallest, highest efficiency, step-up dc-to-dc converters for driving two to 10 white LEDs in series.
They regulate with a constant current, providing efficient display backlighting in PDAs, cell phones, and other handheld devices.
The step-up dc-to-dc converter includes an internal 40V, low drain-source on-resistance, N-channel MOSFET switch for high efficiency and maximum battery life.
The MAX1553/MAX1554 are available in a 3mm x 3mm, 8-pin TDFN package, making them the smallest devices for powering 10 white LEDs.
The MAX1553's current limit of 480mA drives two to six white LEDs. At 20mA from a 3.6V input voltage, it drives six white LEDs with 88% efficiency.
The MAX1554's current limit of 970mA drives up to 10 white LEDs with 82% efficiency at 20mA from a 3.6V input voltage.
The MAX1553/MAX1554 have an adjustable overvoltage protection circuit. This protection circuitry stops the internal MOSFET from switching if the LED string open-circuits due to a fault and prevents the output from soaring.
A single Dual Mode input adjusts brightness through a PWM signal or a direct dc voltage. A separate enable input provides on/off control. Soft-start minimises inrush current during startup.
The MAX1553/MAX1554 are screened for the extended industrial temperature range (-40°C to +85°C).