Application Note
39 of 63
V 1.2
2018-12-12
5 Output PMIC Controller/ IRPS5401
User guide with DB295 and DB296 demo boards
Given this information, the total power dissipation in the IRPS5401 is (6.26 W-(2*0.436 W)-(2*0.182 W)) 5.024 W.
This includes the 0.52 W (12 V*0.043 A) dissipated in the internal LDO + gate drive + controller.
The reported junction temperature for SW-A and SW-B is 77°C. The reported junction temperature for SW-C+D
is 81°C. In this application nearly all the heat is being transferred to and dissipated in the copper of the PCB so
the junction temperature and case temperature are essentially the same.
The 1
st
IR image shows that the case in the area of C/D FETs is at 81°C. The temperature rise above ambient is
(81°C - 25°C) 56°C. The thermal impedance of the IRPS5401 for this particular thermal solution with no airflow
is 56°C/5.024W = 11.1°C/W. The measured case temperature (81°C) is better than the GUI estimate or 93°C.
Figure 54
Reported junction temperature
The thermal image of the entire board shows the PCB in the area of the IRPS5401 is ~60
˚
C. The thermal
impedance from case (and junction) to PCB is (81°C - 60°C) 21°C/5.024W ~ 4°C/W.
