Datasheet AL8116 (Diodes) - 9

AL8116 Functional Description and Application Information Operating Overview
The AL8116 is an excellent 3-in-1 dimming signal interface controller for LED commercial lighting applications. It integrates many functions to reduce the external components’ count and the PCB board size. The AL8116 can convert the three different inputs of dimmer type including 0 to 10V DC linear dimming, 0 to 100% duty cycle PWM (pulse width modulation) signal and a simple resistive potentiometer to an output PWM signal. The output of AL8116 is an open-drain configuration that can pull down any source directly to control power supply dimming. The DIM pin of AL8116 provides an adjustable bias current, thus it can be compatible with both active and passive 0 to 10V dimmers, meanwhile potentiometers. It also can be used in an isolation dimming control via an opto-coupler with combination use of Diodes Incorporated’s primary side dimmable LED drivers AL1665 and AL1666.
Startup and Under Voltage Lockout (UVLO)
A UVLO comparator is embedded to detect the voltage on the VCC pin to ensure the supply voltage enough to power on the AL8116. The turn-on and turn-off threshold voltages are fixed at VCC_ON (7V) and VCC_OFF (6V) respectively. When the voltage of VCC pin is above VCC_OFF (6V), the AL8116 will generate PWM output based on the input DC voltage, PWM signal or potentiometer.
Bias Current of DIM Pin
The ISET pin of AL8116 is used to set the bias current of DIM pin by a resistor (RISET), which is connected between ISET pin and GND. For the typical application, the output bias current of DIM pin is 100μA when RISET is 100kΩ. The relationship between resistor and output bias current is: 2.5V IDIM = × K R DIM ISET Where, KDIM is a coefficient of current ratio of IDIM to ISET. The resistance range of RISET is recommended from 33kΩ to 330kΩ and the range of bias current is 30μA to 300μA correspondingly.
Minimum Output Duty Cycle
When the input of DIM pin is DC potential, the CLAMP pin of AL8116 can set minimum output duty cycle by a resistor (RCLAMP) on CLAMP pin which is connected to GND. There are four modes for users to select. Please refer to the below Table 1. The relationship between the RCLAMP resistor and the voltage on CLAMP pin is below formula. 2.5V VCLAMP = ICLAMP × RCLAMP = × K R CLAMP × RCLAMP ISET Where, KCLAMP is a coefficient of current ratio of ICLAMP per IISET. Table 1. Minimum Output Duty Cycles Clamping Selection Suggestion RCLAMP (Ω) Minimum Output VCLAMP (V) When RISET = 100kΩ Duty Clamping <0.5 0 (Short) 8% 1 to 2 150k 6% 2.6 to 3.6 300k 4% >4.2 >510k (Open) No Clamping The minimum output duty cycle is clamped when VCLAMP < 4.2V; When the DIM Pin voltage (VDIM) decreases from 10.2V to VDIM_OFF = 1.3V, the output duty cycle decreases from 100% to the minimum output clamping duty, which is set in Table 1. When the VDIM signal increases from VDIM_ON = 1.4V to 10.2V, the output duty cycle increases from the minimum output clamping duty to 100% accordingly. There’s 100mV hysteresis for VDIM_OFF and VDIM_ON voltage. The dimming curve is shown in Figure 3a. When VCLAMP ≥ 4.2V, the minimum output duty cycle will not be clamped and it can reach 0%. Thus, the output duty cycle can be adjusted from 0% to 100%, shown in Figure 3b. AL8116 9 of 13 April 2020 Document number: DS42629 Rev. 2 - 2
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