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Supplement the MAX6948 WLED driver with external PWM control

Posted: 07 Jan 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 cellphones. 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 cellphone 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.

Click here to view related datasheets.

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