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AS1122

Datasheet - D e t a i l e d D e s c r i p t i o n

Scrambled PWM

General

Due to the possibility to interrupt a running PWM cycle the AS1122 is useing a scrambled PWM. The advantage is, that the scrambled PWM will

cause less error as the classical PWM when data is updated during a running PWM cycle.

As an example, we take a look on a system with a 8-bit PWM and three LEDs. The PWM for the red LED is set to 4, for green to 2 and for blue

to 6. In the classical approach the red, green and blue channels are high according to their PWM setting (see Figure 38).

If this PWM cycle would be interrupted at the 4th clock, the red and the blue LED would be as bright as if the PWM setting were 8. The green

LED also would be much brighter than desired.

In the scrambled PWM the on-times are divided evenly over the whole PWM cycle. So if the running PWM cycle is interrupted, the failure is less

effective.

Figure 38. Classic PWM vs. scrambled PWM