AS1122
Datasheet ꢀ Detailed Description
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 8ꢀbit 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 onꢀtimes 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
www.austriamicrosystems.com/LEDꢀDriverꢀICs
Revision 1.00
17 ꢀ 22
AMSCO [ AMS(艾迈斯) ]
