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TLC59711 PWM frequency
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TLC59711 PWM frequency

by Bautastein on Mon Apr 19, 2021 10:52 am

Hi

I don't really have a question per se, I just wanted to point out that there seems to be a slight error in your forums, or should I say that you are slightly underselling your product. When searching for "TLC59711 PWM frequency" on google, this thread is the first one that comes up:

viewtopic.php?f=22&t=51859

In fact, google has even made an "answer box" on top, which explains that the PWM frequency of the board is "only" about 153 Hz.

After investigating it further, I found that the IC slices the full PWM period into 128 smaller periods. Whatever value you send to an LED, 0...65535, it tries to evenly distribute the ON time across the 128 bins. So, if you set the value to 1, you will se a 100 ns flash 153 times per second. With value 2, you get twice that frequency, etc...

If you only set values that are multiples of 128, you will get about 20 kHz blinking, where each on period is exactly the same length.

So I think it would be more correct to say that you have a 20 kHz PWM frequency with 9 bits of resolution, and dithering to support an additional 7 bits of resolution.

I tried to check this with my multimeter, so I set an LED to value 32768 (half on), and measured the frequency. I got somewhere around 19.5 kHz.

I couldn't answer the old thread, because it was locked, but I thought it would be good to make Adafruit aware of it, because it really is a fantastic product, so people should know what it's capable of... :)

Bautastein
 
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Please be positive and constructive with your questions and comments.