AL1783

Document number: DS43199 Rev. 2 - 2

9 of 14

www.diodes.com

November 2020

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AL1783

Application Information

Linear LED Driver Design Topology and Implementation

The AL1783 adopts a multi-channel Linear LED driver topology with independent PWM dimming, and current setting control implementation for

each channel. The parallel Linear LED driver channel structure associated with the power conversion stage covers mainstream applications for

many LED Lighting dimming and color tuning applications. Given the maximum operating input voltage at 60V, it is possible to drive more than 16

RGB emitters by splitting LED Emitter string voltage and VIN, as long as it is below 60V.

The AL1783 is a three PWM current sink regulator. In order to meet channel current accuracy and short protection requirements, the

recommended maximum current of each channel is 250mA and the recommended minimum channel current is 30mA. Each channel can be

individually and digitally controlled by the PWM dimming the signal down to less than

maximum output current for Channel 1, Channel 2, and Channel 3 will be 250mA when each PWM signal is turned on. The associated micro-

adjustment is needed.

The LED Driving Element detects fault conditions and reports its status on the FAULTB pin. It features LED open detection, LED short detection,

Over Temperature Protection (OTP), and Under Voltage Lockout (UVLO). The AL1783 provides supreme current matching between channels and

devices. Along with bus-mode fault reporting, multiple devices can be employed together to increase current driving capabilities or channel count

versatility.

Interface with Emitter Strings

The Power Conversion stage provides necessary constant output voltages (CVs) to power the micro-controller unit (MCU), LED Strings, and LED

Drivers. A typical application requires 3.3V for the MCU and 12V/24V/48V anodes of LED emitter strings. The cathodes of the bottom LED emitter

strings are connected to the LED1,2,3 pins of the AL1783.

Interface with MCU

The physical layer interfaces between the micro-controller unit (MCU) and the AL1783 are the PWM1,2,3 pins and FAULTB. The MCU activates

the PWM1,2,3 (asserted high) to turn on AL1783 during normal LED lighting operation applications. When the PWM1,2,3 pins are asserted low

and greater than > 4ms, the device enters into Standby Mode with minimum power consumption. For typical light dimming or mixing operations,

the MCU generates proper dimming control output signals to the PWM1,2,3 pins. If any general fault occurs in the AL1783, the FAULTB pin is

asserted LOW to interrupt and request the MCU to take proper actions.