SBOA523 July   2021 TMP390 , TMP392

 

  1.   Trademarks
  2. 1Temperature Switch Introduction
    1. 1.1 Temperature Switch Design Using Discrete Components
    2. 1.2 Replacing Discrete Solutions With TMP390
  3. 2Alternative Applications
  4. 3Conclusion
  5. 4References

3 Conclusion

In many applications, designers need to be able to detect and react to thermal events, especially in thermally sensitive systems. One way to implement this is to use a temperature switch. This can be done using only discrete components or using the TMP390 or TMP392, as discussed within this report. Table 3-1 summarizes the differences in using only discrete components and using the TMP390 or TMP392.

Table 3-1 Discrete Solutions versus TMP390 and TMP392

TMP390, TMP392

Discrete Solutions

TMP390, TMP392 Benefits

Smallest Circuit Area

6.55 mm × 4 mm (26.2 mm2)

7.22 mm × 6.25 mm (45.1 mm2)

42% smaller PCB area
Minimum Number of External Components4 resistors + 1 cap8 resistors (including thermistor) + 1 caps + 1 op amp50% fewer components
Minimum Number of 1% Tolerance Resistors

4

7

43% direct cost saving for 1% resistors
PCB ConsiderationNo viasMinimum of 3 viasImproved PCB manufacturing costs
Trip TestYesNoSupports production self-test
Circuit FlexibilityNo re-design, simple swap of resistorsCircuit needs to be re-designed and testedFaster time to market
Dual Trip Temp with Single Output

Open drain outputs; simple tie-off

Need additional circuit to connect output of 2 op amps

Flexible and simpler design layouts

Accuracy

Higher

Lower

Allows for better operation in thermally sensitive systems

Power Consumption

Very Low

Very High

Allows for use of a battery as a power supply and increases portability and flexibility of system

Overall CostLowerHigherReduced manufacturing costs due to less components

After extensive comparisons have been made between discrete solutions and the TMP390 or TMP392, it is evident that to reduce size, cost, power consumption, and have high accuracy, the TMP390 or TMP392 offer the best solution. In addition to its low price and small size, it is easy to implement and integrate into a system, with high flexibility in controlling the desired thresholds by changing external resistors that can be chosen via a lookup table.