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AS7221

Functional Description

Datasheet

• PUBLIC

DS000479

• v4-00 • 2019-Jun-28

│ 21

SYNC pin is left open, synchronization is automatically disabled by the internal pull-up connected to

the SYNC/RESN pin.

Refer to Figure 17 below. When pulled down for more than 100 ms the SYNC/RESN pin will reset the

AS7221

Smart Lighting Manager. In this case, the push button “overrides” the output of the opto-

coupler. Therefore, a resistor should be placed in series with the opto-coupler.

Figure 17:

Synchronization and Reset

7.5

PWM Outputs

The AS7221 outputs, used to control dimming and LED warm/cool strings can be configured as either

three PWM outputs, two PWMs and one analog output, or two PWMs. The PWMs are 7-bit for direct

configuration, 12-bit for automatic scaling (daylight and color tune algorithm) and factory set to 886 Hz.

Refer to Figure 18. If necessary, an adjustment of the PWM output frequency from 100 Hz up to 4 kHz

is possible.

The three PWM outputs, PWM_1, PWM_2 and PWM_3 all switch with the same frequency, but are

not simultaneous for better EMI performance.

The PWM_1 output can be set to either analog (0-VDDHV) or digital (0-VDDHV) dimming. Analog

dimming range is 0-100%. Digital Dimming range is 0-100%. PWM2 and PWM3 are used for cool

white and warm white LED color controlling. The cool white LED string needs to be connected to

PWM2 and the warm white LED string to PWM3 accordingly. Range is 0-100% for both PWM2 and

PWM3. If the external dimming device does not support the full range 0-100% it is possible to adjust

the low end of the dimming range via the ATDMLTL smart lighting command.

For test and scene configuration purposes 2 direct PWM AT-commands are available. ATXPWMx can

be used for scene confiruations. It allows a direct PWM input at the scene ramp generator and

override all PWM values calculated by the AS7221. ATPWMx can be used for hardware tests. It

Opto Coupler

VDD

AC Main

CLE

SYNC/

RESN

10k

optional

SYNC and Reset

Push > 100ms

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