Test condition:
1. Measure the thermal couple under surface temperature, Tc is 58.1°C
2. TPS54426 the = 51.3(°C/W)
3. Pd=0.85 Watt.
4. This package have the Thermal pad. (We have to mount a PCB).
5. Not include Thermal pad condition =101.7°C
Question:
How could I evaluation of? (Need consider the Thermal pad condition)
Q1.How to use this formula (Tj=Pd*Rjc+Tc) to calculate?
(Need consider Thermal pad containing proportional relationship both with Tc.)
Q2.Why the Rjc>Rja from the TPS54426 specification?
( formula Rja=Rjc+Rca, normally the Rja > Rjc)