How much is the current consumption of this sensor (tmp102)?
If you look at Figure 3, you'll see that conversion time is a function of both supply voltage and temperature, ranging from 26 ms to 30 ms.

Looking at the Electrical Specifications on page 3, under Power Supply, the power consumption with the bus inactive is less than 0.5 &micro;A in shutdown mode, and up to 10 &micro;A otherwise. However, note that the bus interface draws power in proportion to the activity on the bus, independent of the mode of the sensor, and this can add up to an additional 80 &micro;A at high bus speeds (3.4 MHz).