02 August 2011
12bit pwm generator offers dynamic led control
Linear Technology has unveiled a new pulse width modulation (pwm) generator with 48 independent channels. According to the IC specialist, each channel has an individually adjustable 12bit (4,096 steps) pwm register and a 6bit (64 step) +50% correction register. All controls are programmable via a simple TTL/CMOS 50MHz serial data interface.
The LT8500 is designed for use in a variety of pwm intensive applications, such as led control, as well as industrial and robotic applications. It can be used with three LT3595As, 16 channel led drivers, to deliver 48 independently dimmed led strings for locally dimmed led backlighting for large lcd displays. The correction resister allows matching light output of each led string.
The device operates from a 3 to 5.5V input range, enabling it to operate from a range of standard power buses. For led applications, each channel has individual 6bit dot correction current adjustment and 12bit gray scale pwm dimming. The 40ns on time of the LT8500 is said to offer wide dynamic contrast ratios. Both correction and gray scale dimming are accessible via a serial interface in TTL/CMOS logic.
The LT8500 offers two diagnostic information flags: synchronisation error and open led. The flags are sent with additional state information on the serial data interface during status read back. The 50MHz cascadable serial data interface includes buffering and skew balancing to ease the design for pwm intensive applications such as large screen lcd dynamic backlighting.
The generator is available now in a 56 lead 5 x 9mm QFN package
Author
Laura Hopperton
Supporting Information
Websites
http://www.linear.com
Companies
Linear Technology (UK) Ltd
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