AL1663RS-13 datasheet(10/15 Pages) DIODES

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AL1663/AL1663R

Document number: DS38466 Rev. 2 - 2

10 of 15

www.diodes.com

March 2017

AL1663/AL1663R

100

PWM Duty (%)

Application Information (Cont.)

Dimming Mode

The AL1663 can support three dimming modes: analog dimming, PWM-to-DC dimming and PWM dimming.

The AL1663R can support two dimming modes: analog dimming and PWM dimming.

1. Analog Dimming Mode

In analog dimming mode, the dimming signal is added to APWM pin directly to realize dimming function. The setting circuit is shown as Figure 4. A

capacitance of hundreds nF is recommended for CAPWM. When VAPWM is higher than 2.4V, the driver will output 100% of rated current; when the

voltage VAPWM is in the range from 0.3 to 2.4V, the output current will change linearly with the voltage VAPWM. When VAPWM is lower than 0.3V,

switch will be turned off and the output current drops to zero. The dimming curve is shown as Figure 5 and the dimming range is from 12% to

100%.

Figure 4. Analog Dimming Setting Circuit

Figure 5. Analog Dimming Curve

2. PWM-to-DC Dimming Mode

In PWM-to-DC dimming mode, PWM dimming signal is added to PWMD pin. The setting circuit is shown as below Figure 6. A capacitance of

hundreds nF is recommended for CAPWM. The duty cycle of the dimming signal DDIM is reflected by the voltage on APWM pin VAPWM.

2.4

APWM

DIM



Where DDIM is duty of PWM signal; VAPWM is the voltage of APWM pin.

Thus the output current will change with the duty cycle of dimming signal DDIM. For example, the dimming curve is shown as Figure 7. The

dimming range is 12% to 100%.

Figure 6. PWM to DC Dimming Setting Circuit

Figure 7. PWM to DC Dimming Curve (PWM Frequency is 500Hz)

3. PWM Dimming Mode

In PWM dimming mode, dimming signal will be added to APWM pin .The setting circuit is shown as Figure 8. The output current is chopped by the

dimming signal directly. The logic high level of the dimming signal needs to be higher 2.4V while the logic low level is lower than 0.3V. Switch is

turned off at logic low level. The dimming curve is shown as Figure 9. The dimming range can be 100 to 1% with 1kHz frequency of PWM signal.

Figure 8. PWM Dimming Setting Circuit

Figure 9. PWM Dimming Curve (PWM Frequency is 1 KHz)

0.0

0.5

1.0

1.5

2.0

2.5

3.0

100

APMW

(V)

100

PWM Duty (%)

APWM

AL1663/AL1663R

0.3-2.4V

Dimming Signal

APWM

PWMD

AL1663

APWM

AL1663/AL1663R

PWM Dimming Signal

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