TMP117 datasheet(33/45 Pages) TI1

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Temperature (qC)

-50

-25

100

125

150

175

700 uWt

630 uWt

500 uWt

410 uWt

370 uWt

225 uWt

Time (Sec)

D014

1.9 V

3 V

TMP117

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SNOSD82 – JUNE 2018

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Application Information (continued)

8.1.1.2.3

Self-Heating Effect (SHE)

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 38 shows the

device SHE in still air at 25°C after the supply is switched on. The device package, including the thermal pad, is

soldered to the 11-mm × 20-mm × 1.1-mm size coupon board. The board is located 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 38, the SHE stabilization time in still air is greater when the device dissipates more power.

Figure 38. Self-Heating in Still Air vs. Temperature and Dissipated 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 39 shows the SHE drifts versus temperature and dissipated power at 25°C for the same coupon board

and the same conditions described previously.

Figure 39. Self-Heating in Still Air vs. Temperature and Dissipated Power at 25°C

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 39. 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.

TMP117 Datasheet(PDF) 33 Page - Texas Instruments