General Power Dissipation Considerations
2-7
Evaluation Module Layout
2.5 General Power Dissipation Considerations
For a given θJA, the maximum power dissipation is shown in Figure 2–4 and is calculated by the
following formula:
PD
TMAX–TA
JA
Where: PD= Maximum power dissipation of Txxxx IC (watts)
TMAX= Absolute maximum junction temperature (150°C)
TA= Free-air temperature (°C)
θJA = θJC + θCA
θJC = Thermal coefficient from junction to case
θCA = Thermal coefficient from case to ambient air (°C/W)

Figure 2–4.Maximum Power Dissipation vs Free-Air Temperature

2
1.5
1
0–55 –25 5
Maximum Power Dissipation – W
MAXIMUM POWER DISSIPATION
vs
FREE-AIR TEMPERATURE
35
TA – Free-Air Temperature – °C
65 95 125
SOIC (16-pin)
Package
Low-K Test PCB
θJA = 114.7°C/W
SOIC (8-pin)
Package
Low-K Test PCB
SOIC (14-pin)
Package
Low-K Test PCB
TJ = 150°C
0.5
NOTE A: Results are with no air flow and using JEDEC Standard Low-K test PCB.

Table 2–1.Dissipation Rating Table

PACKAGE θJC
(°C/W)
θJA
(°C/W) TA ≤ 25°C
POWER RATING
D (8) 38.3 176 710 mW
D (14) 26.9 122.3 1022 mW
D (16) 25.7 114.7 1090 mW