Power Electronics

48-Channel PWM Generator Controls LEDs

Linear Technology announces the LT8500, a pulse width modulation (PWM) generator with 48 independent channels. Each channel has an individually adjustable 12-bit (4,096 steps) PWM register and a 6-bit (64 step) ±50% correction register. All controls are programmable via a simple TTL/CMOS 50MHz serial data interface. The LT8500 can be used in a wide variety of PWM-intensive applications such as LED control, as well as industrial and robotic applications. For example, the LT8500 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 LT8500 operates from a 3V to 5.5V input range, enabling it to operate from a wide range of standard power buses. For LED applications, each channel has individual 6-bit dot correction current adjustment and 12-bit gray scale PWM dimming. The 40ns on-time of the LT8500 offers very 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: synchronization 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, easing the design for PWM-intensive applications such as large screen LCD dynamic backlighting. The combination of minimal externals and a 5mm x 9mm QFN package provide a highly compact solution footprint for multichannel PWM applications.

The LT8500EUHH is available in a 56-lead 5mm x 9mm QFN package, priced starting at $2.95 each, in 1,000-piece quantities. The extended temperature version, the LT8500IUHH, or I-grade, is also available, priced starting at $3.25 each in 1,000-piece quantities. All versions are available from stock.

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