• We recently switched our forum platform. If you experience any issues please email support@crystalfontz.com

CFAG16080A-TMI-TZ pwm dimmed backlight flickering


New member

I use a pwm dimmer (PCA9530) to control the backlight on my CFAG16080A-TMI-TZ. There is flickering on the backlight when i set the duty cycle below 30% and it gets worst as it goes down. I can see the flickering even more if i look the lcd at an angle.

Since the PCA9530 outputs can't handle large currents, i used a NPN transistor (BST39) to switch the backlight.

The PCA9530 is located about 5 inch away from the transistor on an another board. It looks like there is jitter on the pwm signal. I don't know that for sure since i don't have an oscilloscope to test it.

What can i do to filter the signal?

Thank you
Looking for additional LCD resources? Check out our LCD blog for the latest developments in LCD technology.



New member
152Hz. This is the maximum frequency the PCA9530 can provide... nothing i can do about it...

If i understand correctly, the flickering is due to the lcd refreshing the display faster than the pwm signal causing a strobe light effect that allow me to see the "scan line"

This makes sense, because when i set the duty cycle to the lowest setting, i can actually see the "wave".

I'm going to try to find a faster PWM. but before i do so, is there something i can do to fix this?


New member
I found the solution...

I can't make the pwm go faster, but i found a way to make the lcd to refresh slower. I set the LCD display duty to 98 instead of 80 and re-adjusted the contrast... It works great now.

Thanks CV.