SLYT793A may   2020  – may 2020 LM61460-Q1

 

  1.   1
  2. 1 Introduction
  3. 2 Managing Thermals with Flip-chip Packages
  4. 3 Board Construction Influence
  5. 4 Copper Area and Thermals
  6. 5 Estimating a Converter’s Junction Temperature
  7. 6 Challenges with Measuring Converter Junction Temperature
  8. 7 Further Thermal Optimization at the IC Level
  9. 8 Conclusion
  10. 9 References
  11. 10Related Web Sites
    1. 10.1 General Information:
    2. 10.2 Product Information:

6 Challenges with Measuring Converter Junction Temperature

It can be difficult to measure the converter junction temperature in an enclosed temperature chamber. Using a thermocouple can be ineffective, as it can remove heat from the package topside. This leaves a current or voltage measurement as an alternative way to determine the converter’s junction temperature.

Converters have an electrostatic discharge diode on each pin to protect the device from static discharge. Additionally, some pins may have a FET between them; for example, the PGOOD pin has an open-drain FET from PGOOD and ground. Characterizing the voltage drop on the body diode of this FET allows for an approximation of the junction temperature.[2] Unfortunately, due to switched waveforms in the IC (and sometimes the IC layout), characterizing a diode in the IC is not always a clear-cut process. Additionally, the diode measurement must not influence the normal operation of the device.