Linear Technology has announced the LT8500, a PWM generator with 48 independent channels. Each channel has an individually adjustable 12bit of 4,096 steps PWM register and a 6bit of 64 steps ±50% correction register. All controls are programmable via a simple TTL (transistor transistor logic) and CMOS 50MHz serial data interface. The generator is suitable in 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 dimmed LED backlighting for large LCD displays. The correction register allows matching light output of each LED string. The generator operates from 3 to 5.5V input range. For LED applications, each channel has individual 6bit dot correction current adjustment and 12bit gray scale PWM dimming. The 40ns on-time of the generator offers wide dynamic contrast ratios. Both correction and gray scale dimming are accessible via a serial interface in TTL and CMOS logic.
The generator provides two diagnostic information flags such as 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, minimises the design for PWM-intensive applications such as large screen LCD dynamic backlighting. The generator is available in a 5x9mm QFN package. Two grades of the generator are available: the LT8500EUHH, which is available in a 56-lead 5x9mm QFN package, and the LT8500IUHH or I-grade, which is the extended temperature version.
