What small IC could give switchable I2C pullups?
I would suggest &quot;prebiased&quot; BJTs
Dual MOSFETs tend to have a lot of Drain-Source capacitance which will affect the rise time of your I2C bus. BJT switching transistors tend to have less. For example, these ones have Cob of only 3pF typically at 10V (it will be 2-3 times higher at low voltage, which they don't tell you and you're supposed to know) but that's still pretty modest. Add the pullup resistors to the collectors, the emitters to Vdd, and connect the bases to your /enable line and you're done (one part plus the resistors, and the package is only 2.0 x 2.1mm). Very cheap in volume, and not much worry about ESD.




simulate this circuit &ndash; Schematic created using CircuitLab

So why not MOSFETs?
They're lower resistance, right? Well the saturated BJTs will drop 50~100mV most likely at the currents you'll be using them (compares well with 4066 switches), and compare the output capacitance of an FDS6312P MOSFET (Coss)- typically several hundred pF near 0V, which is nearly as high as the 400pF maximum for all devices on the bus itself.