SNOSD82C June 2018 – April 2021 TMP117
During ADC conversion, some power is dissipated that heats the device despite the small power consumption of the TMP117. Consider the self-heating effect (SHE) for certain precise measurements. Figure 8-2 shows the device SHE in still air at 25 °C after the supply is switched on. The device package is soldered to the 11-mm × 20-mm × 1.1-mm size coupon board. The board is placed horizontally, with the device on top. The TMP117 is in continuous conversion mode with 64 sampling averaging and zero conversion cycle time. There is no digital bus activity aside from reading temperature data one time each second. As shown in Figure 8-2, the SHE stabilization time in still air is greater when the device dissipates more power.
The SHE drift is strongly proportional to the device dissipated power. The SHE drift is also proportional to the device temperature because the consumption current with the same supply voltage increases with temperature. Figure 8-3 shows the SHE drifts versus temperature and dissipated power at 25 °C for the same coupon board and the same conditions described previously.
To estimate the SHE for similar size boards, calculate the device consumption power for 25 °C and use the corresponding power line shown in Figure 8-3. For example, in CC mode without DC at a 3.3-V supply at 25 °C, the device dissipates 410 µWt. So self-heating in still air is approximately 40 m°C for the described condition and rises to 52 m°C at 150 °C.
The following methods can reduce the SHE: