Allegro Develops Multi-Output LED RGB Driver IC

The A8512 from Allegro Microsystems is a multi-output white LED RGB driver IC for the LED backlighting of large-area LCD monitors and television screens. The device integrates a scalable-output boost controller operating in constant-frequency current mode control - adjustable between 300kHz and 1MHz - driving an external Mosfet. It integrates six internal current sinks, each capable of sinking up to 80mA, which can be combined together to achieve even higher currents.

PWM dimming allows LED currents to be precisely controlled over a 500:1 ratio as a percentage of the maximum setpoint determined by the user. Multiple A8512 devices can be connected in parallel, with one master controller governing the boost stage and up to five slave controllers acting as LED sinks. This configuration allows up to 36 LED strings to be powered by a single boost converter, reducing the number of external components required. Other features include controlled start-up using enable, PWM signal or battery voltage ramp and active current sharing between LED strings with +/-0.6 per cent accuracy and matching.

There is no audible MLCC noise during PWM dimming. The A8512 operates from a single supply of 8-24V. It provides protection against over voltage, open or short-circuited LED string and over temperature. A dual-level cycle-by-cycle current-limit function provides soft start and protects against overloads. The A8512 is available in a 28-contact 5mm x 5mm QFN package (ET), with an exposed thermal pad for enhanced thermal dissipation. For single-sided PCB manufacturing capability, the device is also available in a 24-pin SOICW package (LB), with internally fused pins for enhanced thermal dissipation. Both packages are lead free, with 100 per cent matt tin lead-frame plating.

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