Gerhard Fiedler wrote:

> are there any ICs around that implement some current source pullups
> (eg. a fet and a resistor each), eg. in a sip case like those resistor
> networks?

  That concept naturally occurred to me when I wrote the commentary.  A
current source does make a much better pull-up component.

  The AVR also uses current sources.  The datasheets show them as FETs
but give (IIRC) an equivalent resistance.  That's not entirely un-
reasonable, as it presumably indicates their effective resistance when
pulled to ground.

  Presuming however they maintain that current almost all the way up to
the power rail, they should work far *better* than the equivalent
resistance, including their interference rejection.
--
  Cheers,
        Paul B.