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Supplement the MAX6948 WLED driver with external PWM control

Posted: 01 Jun 2010     Print Version  Bookmark and Share

Keywords:WLED driver  MAX6978 driver  PWM control 

The MAX6948 WLED driver accepts input voltages between +2.7V to +5.5V and boosts the output voltage up to +28V to drive the backlight in cell phones. If the nominal forward voltage of a WLED is 3V, then the MAX6948's 28V-rated high-voltage port can be used to drive 9 WLEDs in series for cell phone LCD screen backlighting. This high-voltage port provides a stable current of up to 30mA. The intensity of these serial backlighting LEDs is controlled through a 10bit, 1,024-step PWM mechanism.

The MAX6948 has five other general-purpose ports that can also drive LEDs directly from the battery or be used as open-drain I/Os. When used as LED drivers, these 8V-rated ports provide a constant current of either 10mA or 30mA (max) with 8bit, 256-step PWM intensity control.

This application note explains how to add external PWM intensity control to supplement a device's internal PWM. The MAX6948 WLED driver serves as the example device. Configuration settings and performance data are shown.

View the PDF document for more information.

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