WLED Driver Delivers Backlighting For Netbooks

Maxim Integrated Products introduces the MAX17127, a six-string WLED driver that provides a complete backlighting solution for notebooks and netbooks. The step-up controller integrates a 48V Mosfet capable of driving up to 13 LEDs. This integration reduces BOM cost and saves board space by eliminating an external Mosfet. The step-up controller frequency can be programmed from 250kHz to 1MHz, allowing flexibility in selecting external components.

The MAX17127 features an input voltage range of 5V to 26V, making it suitable for both netbooks that use a two- to three-cell Li+ battery and notebooks that use a larger battery. The current in each string can be programmed from 10mA to 30mA using an external resistor, which helps set the appropriate brightness level. Better than +/-2 per cent accurate current matching between strings ensures even LED brightness. The MAX17127 operates in a direct-dimming mode with a dimming frequency ranging from 100Hz to 25kHz.

The LED current is directly controlled by the external dimming signal's frequency and duty cycle. The wide dimming range eliminates the audible noise issues usually encountered in WLED drivers. A low feedback voltage at each LED string helps reduce power loss and improve efficiency. The MAX17127 offers multiple features to protect the controller from faults, including over current, over temperature, plus open-/short-string conditions. The step-up controller has cycle-by-cycle current limiting and soft-start capability to control inrush current. The MAX17127 is available in a 4mm x 4mm, 20-pin TQFN package and operates over the -40C to +85C extended temperature range.

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