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Sony's CXA Chroma Encoders
Sony's Chroma Encoders provided the video (and sometimes S-video) output of pretty much every modern game console, from SNK, Sony, Sega and others. There are three chips in this series:
- CXA1145/MB3514 (same chip, one made by Fujitsu)
- CXA1645
- CXA2075
The 1145 is the first chip, and it doesn't offer full S-video output. However, you can achieve a decent S-video signal from the chip by amping the two Y/C outputs from pins 15 and 16. See the schematic here The 1145 was used in most early consoles, up to and including the Genesis and Neo Geo. The MB3514 is pin-for-pin the same chip and was used for the Sega CDX and other Genesis models/variants. The 1645 powered many later consoles, including the Genesis 3, Saturn and NeoGeo CD/CDZ. The 2075 was never used in a console as far as I know, however it was considered for use in Sega's Saturn (it used too much power and had to be dropped).
The CXA2075 is the most powerful chip, requiring far fewer external components, and producing better output. Micomsoft used it in later revisions of their X-AV2s encoding product. According to one of the chip's designers it was pretty amazing. It was a drop-in replacement for the 1645, it didn't need an external circuit, and it produced much better output.
Etc
There is some specific application information of the CXA1645 on the GameSX.com site. The Genesis 3 page shows some very detailed info, including images of the chip itself. There's also the HiSaturn Navi RGB page.
Here is a CXA1645 PDF
There is no online version of the CXA1145 PDF, however there are some clone chips with identical characteristics, which have (admittedly shoddy, scanned) PDFs. The chip's designer has a partial version of the CXA2075 PDF on his site.