I am missing some specifications in the ssm2603 datasheet,
that is: maximum low input and minimum high input voltage, as well as output drive capability (max output low voltage) for the I²C pins of this device.
I agree that the digital min and max levels should have been included in the datasheet. This part was designed over 12 years ago so at this point it is not a simple matter to collect and analyze the data to come up with the datasheet specs for this. What sort of product is this being designed into? What will be the projected life of the product and expected yearly volumes?
Regarding the I2C drive capabilities. We generally do not publish the R-on specifications for the I2C pins. This is not characterized and is guaranteed by design to meet the minimum specifications of the I2C bus. So as long as you do not have excess capacitance, and therefore an I2C pull-up resistor that is too low, it will be able to pull down the line below the min spec for the I2C bus. This has not been an issue with any of our parts.
this chip might be designed into our N'th generation of mpeg video encoders. I used it in previous ones and for simplicity wanted to reuse it this time too. Volume for the next encoder should be around 1k/year for few years. I'm asking because I currently want to verify signal integrity on the I2C bus, which is loaded with several different chips of different kind. I2C signal integrity has become a rather nasty situation, given such funny ideas as having a "low" and a "super low" level for certain bus repeaters, and such ideas as having active rise time accelerators of various kinds. Further you usually have meanwhile a mix of power supplies for the chips, with a rather mix of input level thresholds, presence or absence of upper clamping diodes, presence or absence of glitch filters etc etc. All in whole a rather mess considerably amplified if manufactures simply wont tell whats in their specific incarnation of an I2C interface. It simply would have been helpfull if there would have been a statement in the datasheet, like other manufacturers usually do have.