Apologies, I know you are trying to tell me something, but I'm not getting it. I believe the charts already reflect what you are saying - the max ratings are not used anywhere and the dissipation values in the tables are developed from Rds(on) and necessary to evaluate acceptable no-heatsink operation.
fechter wrote:In this application, the FET is not trying to dissipate much, so we should not be getting even remotely close to the maximum dissipation ratings, so they don't matter that much.
The Rds matters a lot as does the voltage rating.
Yes - I noted that above - the Id value for silicon in the lower parts table is an FYI - it's not used anywhere. The Vdss is not used either. They are there simply to put FET stats that are commonly called out as significant in handy view so that posted snaps of a chart give the whole FET picture. So, those common specs are unused, but harmless.
The entire chart is based on the Rds(on) spec. The dissipation values in the tables are derived from applying the fractional part of the battery current in the first column to the Rds(on) value according to the number of FETs - a simple approximation barring layout factors. The resulting dissipations are as noted in the table cells and clearly far below the max. These are compared to the dissipation values calculated in the parts spec table at 85/125 degC to determine the GO/MAYBE/NOGO state (GYR color).
I did see that the first column in each of the FET tables was labelled 'Id' which was arguably incorrect, so I changed the column header to the more appropriate 'Ibatt' both in the post above and in the downloadable zip file. Perhaps that made things unclear...