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digital RGB LED question

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glenenglish:
I didnt delete anything.
The fundamental freq at 800kHz was a problem . Yu cant meet CISR25 with a transmitter running inside the AM broadcast band
never mind the harmonics.
The problem for the devices was the lack of harmonics (IE being not square waves, IE without necessary fast risetimes to ensure the transition between 0 and 1 is fast enough to avoid the chip toggling states internally as it passes through the threshold band.),

tooki:

--- Quote from: glenenglish on April 26, 2024, 09:04:32 pm ---I didnt delete anything.

--- End quote ---
I know you didn’t, which is why I never said you did. I said that the post you were REPLYING TO was deleted. See your replies #5 and 6 above? There used to be another post between them. That post was from someone else. They deleted it after you replied to it.


--- Quote from: glenenglish on April 26, 2024, 09:04:32 pm ---The fundamental freq at 800kHz was a problem . Yu cant meet CISR25 with a transmitter running inside the AM broadcast band
never mind the harmonics.

--- End quote ---
So wouldn’t the harmonics have made EMI emissions even worse?!


--- Quote from: glenenglish on April 26, 2024, 09:04:32 pm ---The problem for the devices was the lack of harmonics (IE being not square waves, IE without necessary fast risetimes to ensure the transition between 0 and 1 is fast enough to avoid the chip toggling states internally as it passes through the threshold band.),

--- End quote ---
Sure. But that’s not an EMI issue.

Is there some reason you are reluctant to share any of the requested information, like a block diagram? Super frustrating.

glenenglish:
harmonics maybe might have made EMI worse, it depends on their amplitude, which might depend on the cable characteristics, the driver characteristics, the load characteristics...

problem 1-
the lack of sharp edges mean the link is unreliable (those chips need square waves). long periods in the transition region  leads to (even poorer)  RF immunity
problem 2-
signals in the broadcast band on unshielded cables are radiators and likely cannot meet CISPR25 etc emission requirements, and are likely to cause harmful interference to you and your neighbour's listening of the radio.

glenenglish:
well I have some maybe useful info for others.

While the required data cycle time is shown in the data sheets as 800kHz / 1250uS, as long as you stick to the required high times  of 400 and 800nS +/- 100nS, it seems you are good to go

I've tested up to 5uS data bit width (with high time 400nS =0  or 800nS  = 1 ) IE a bit fat chunk of low after the pulse , seems to be fine.

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