Convertors power up handset LEDs

The MAX1553 and MAX1554 are the smallest highest-efficiency step-up DC/DC convertors for driving up to 10 white LEDs in series.

The MAX1553 and MAX1554 are the smallest highest-efficiency step-up DC/DC convertors for driving up to 10 white LEDs in series.

They regulate with a constant current, providing efficient display backlighting in PDAs, cellphones, and other handheld devices.

The step-up DC/DC convertor includes an internal 40V, low drain-source on-resistance, N-channel mosfet switch for high efficiency and maximum battery life.

The MAX1553 and MAX1554 are available in 3 x 3mm, 8-pin TDFN packages, making them the smallest devices for powering 10 white LEDs.

The MAX1553's current limit of 480mA drives between two and 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 and 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 and MAX1554 are screened for the extended industrial temperature range (-40 to +85C).

Prices for the MAX1553ETA and MAX1554ETA start at $1.35 (1000-up, FOB USA).

Evaluation kits are available to speed designs.

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