LED Driver 6 Click is a high brightness LED or LED strip driver, designed to be used in tunable Smart Connected Lighting (SCL) applications. It is based on the AL1781, a single-channel PWM dimmable linear LED driver. By utilizing a high-frequency E-flicker free technology with Deep Dimming capability, it can be used in single-channel tunable white SCL applications. The AL1781 IC features the Adaptive Thermal Management scheme, reducing the power dissipation. It also integrates an abundance of protection features for increased reliability: undervoltage, open or short circuit at the output, and thermal protection.
LED Driver 6 Click is supported by a mikroSDK compliant library, which includes functions that simplify software development.
The AL1781 integrates a low-side current sink which allow LED strips or LED bulbs to be connected in the common-anode topology for increased effectiveness and power optimization. This IC is designed with the power optimization in mind: whenever there is no valid PWM signal on its input pin, it enters the low-power mode, preventing unnecessary power dissipation. An additional ADC IC is used, allowing advanced power optimization. Offering good reliability, linear dimming response, and low power consumption, LED driver 6 Click is a perfect solution for smart lighting applications, SCL LED bulbs, but also for driving LED strips and high-power LEDs.
LED Driver 6 Click is based on the AL1781, a single-channel PWM dimmable linear LED driver by Diodes Incorporated. It is a constant-current driver, which can sink up to 1500mA. It has a low-side current sink which allow LED strips or LED bulbs to be connected in the common-anode topology for increased effectiveness and power optimization. The constant current through the connected LED can be selected by a SMD jumper labeled as ILED, between two values: 1A and 1.5A.
The AL1781 IC can be operated with a PWM signal in the frequency range from 1kHz to 40kHz. By applying the PWM signal with the duty cycle of less than 4ms, it is possible to tune the light intensity of the connected LED light element. A LOW pulse width of more than 4ms will set the device into the low-power mode (suspend). The lowest light intensity that can be reached by applying the PWM frequency of 1kHz is 0.1%, while 40kHz allows the lowest brightness level of 4% of the full light intensity. A High PWM frequency allows for less visible flickering, but limits the lowest light intensity level, at the same time. PWM1 and PWM2 pins of the AL1781 are routed to the mikroBUS™ PWM and CS pins and are labeled as PW1 and PW2.
Adaptive Thermal Management (ATM) scheme is one of the key features of the AL1781. It can be used to optimize the power consumption by adjusting the voltage of the external power supply unit (PSU): the excessive voltage applied to the connected LED will be dissipated as heat within the AL1781 IC. Therefore, the voltage level of the external PSU should be kept above the forward voltage of the connected LED plus minimum voltage headroom (VF + VLED_REG). The ATM injects current through the LEDPG pin of the AL1781. This current is converted to a voltage level, and it is sampled by the MCP3221, a low-power 12-bit A/D converter with I2C interface, by Microchip. It has its I2C pins routed to the respective mikroBUS™ I2C pins, allowing the host MCU to read the LEDPG voltage and make PSU voltage adjustments. Please note that if an external PSU with no external regulation is used, its voltage should stay within the mentioned range (VF of the connected LED element + VLEDx_REG as per AL1781 datasheet). However, the voltage should always stay below 30V.
The AL1781 IC also integrates an abundance of protection features for increased reliability: undervoltage, open or short circuit at the output, and thermal protection. If any of these protections become activated, a fault event will be reported on a dedicated pin, labeled as FAULTB. This pin is routed to the mikroBUS™ INT pin and it is asserted to a LOW logic level when a fault event occurs.
Deep Dimming Capability helps with power efficiency. Subjective perception of the light intensity differs from the measured light. For example, the light intensity of 10% (in respect to the applied duty cycle) is perceived as 32% of the full light intensity. Deep Dimming Capability helps with energy saving, providing an optimal light output. Deep Dimming down to 0.1% is possible with the AL1781 IC, since it can be operated with the pulse width as low as 1 µS, while still providing good linearity.
LED Driver 6 Click is designed to be used along with an external PSU and an MCU. The full potential of the LED Driver 6 Click is achieved when combined with a dedicated ambient light sensing Click board™ such as Ambient 5 Click: by receiving information about the ambient light intensity from Ambient 5 Click, the MCU can generate PWM signal in respect to the required intensity tuning and send it to LED Driver 6 Click to regulate the intensity of the ambient lighting.
This Click board™ is designed to be operated by 3.3V logic levels only. A proper logic voltage level translation should be performed before the Click board™ is used MCUs which are operated at 5V.
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