Re: FPGA NTSC signal with 2 resistors and PWM
- From: "John_H" <newsgroup@xxxxxxxxxxxxxxxx>
- Date: Fri, 28 Sep 2007 09:56:23 -0700
"Antti" <Antti.Lukats@xxxxxxxxxxxxxx> wrote in message
news:1190994565.617357.99810@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
ha, eh the PWM is clocked with 80MHz and for 16 grey levels the PWM
frew is 5 MHz :(
yes i already tried some cap for filter, it makes it a very little
better only
for color signal i guess at least the R-2R thing is needed
I will try without by using 500MHz clocked delta sigma, that should be
much better then 80mhz clocked PWM but not sure if even that is
useable for color.
Antti
At better than 100:1, I'd expect the 500 MHz delta to give good results.
The filtering will be less of an issue for the delta scheme.
Until or unless you have the nice modulator configured, would you consider
using some TV analog filter chips to clean up the video? Your low-cost end
solution might not use a part like the US$0.59 MAX9512 from maxim-ic.com,
but it could make the initial development a little easier.
- John_H
.
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