as it turns out, new video cards no longer have analog video output. There are multiple converters available for sale, but I have not found one that can do higher resolution than 1080p at a refresh rate higher than 60Hz.

So, I though that maybe I should try making one myself, assuming I manage to get the DAC and other required parts for this. I mean, it should not be that difficult other than getting the high frequency signals behaving correctly (which would be a learning opportunity).

However, so far it seems that I am stuck with a chicken-and-egg problem - I do not know enough about the design of such devices to be able to find good information about the design of such devices.

Could anyone point me in the correct direction so I can learn about these things? Or maybe someone has a list of chips that would e useful to in converting video to analog?

EDIT to answer pjc50's comment: I know how VGA (signals) work and I also know that the pixel clock is the reason that pretty much all converters do not support 1920x1200@85Hz. However, since video cards have 400MHz video DACs (well, all except the very latest), this means that someone makes those DACs and I would need to figure out how to feed data to one. Or use a fast general purpose DAC. The problem for me is that I do not know where to start learning about the DVI side of things. I mean there has to be a way to, say, take video from DVI input and put it in a frame buffer in a way that can be read and sent to a DAC.

EDIT2: after reading the example that rioraxe suggested (that was low frequency), I found a possible way to do this:

ADV7619 can take HDMI input and convert it to RGB output and it works for pixel frequencies up to 300MHz. ADV7125 is a DAC designed for driving VGA and operates at up to 330MHz. Both chips are not BGA, though they have a pad on the bottom which will probably be annoying to older, but not impossible. Both chips are not that expensive too.

Now I only need to find a way to interface those two. ADV7619 outputs two pixels at once (300MHz pixel clock results in 48bit 150MHz output), but ADV7125 expects the data to be one pixel at a time at the correct pixel frequency.

How do I convert a 16/48bit parallel bus operating at 150MHz to a 8/24bit parallel bus operating at 300MHz? Any logic chip family operates at these frequencies at 3.3V?

  • \$\begingroup\$ datapro.net/products/hdmi-dvi-d-to-vga-converter.html, buy it, break it open and reverse engineer it. \$\endgroup\$ – winny Nov 17 '16 at 8:33
  • \$\begingroup\$ I suspect the reason you can't get high res ones is that the pixel clock rate would be too high. Are you familiar with the structure of VGA? \$\endgroup\$ – pjc50 Nov 17 '16 at 9:21
  • \$\begingroup\$ @pjc50 I have edited my question to answer your comment. \$\endgroup\$ – Pentium100 Nov 17 '16 at 9:53
  • \$\begingroup\$ Ok, did you look into what is available? For example, LTC2000 can do this output rate. However, each DAC is @100 apiece, so you are looking already at $300, not counting for a sizable FPGA to drive many LVDS parallel ports. Plus BGA boards etc. For this price you can trash your old hot SVGA display, and buy a new modern one. \$\endgroup\$ – Ale..chenski Nov 17 '16 at 17:27
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    \$\begingroup\$ @AliChen dim is good, I mean it is bright enough for me (brightness setting around the middle), while some of the modern monitors are too bright (I have one LCD monitor at work where I had to set brightness to zero and contrast to almost zero to be able to look at it without sunglasses). \$\endgroup\$ – Pentium100 Nov 18 '16 at 4:38

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