THS4081 Datasheet, PDF (18/24 Pages) Texas Instruments – 175-MHz LOW-POWER HIGH-SPEED AMPLIFIERS

THS4081, THS4082
175-MHz LOW-POWER HIGH-SPEED AMPLIFIERS
SLOS274C – DECEMBER 1999 – REVISED MAY 2000
APPLICATION INFORMATION
general PowerPAD™ design considerations (continued)
The actual thermal performance achieved with the THS408xDGN in its PowerPAD™ package depends on the
application. In the example above, if the size of the internal ground plane is approximately 3 inches × 3 inches,
then the expected thermal coefficient, θ_JA, is about 58.4_C/W. For comparison, the non-PowerPAD™ version
+ ǒ Ǔ ^{of the THS408x IC (SOIC) is shown. For a given θJA, the maximum power dissipation is shown in Figure 46 and}
is calculated by the following formula:
PD
TMAX–TA
q_JA
Where:
P_D = Maximum power dissipation of THS408x IC (watts)
T_MAX = Absolute maximum junction temperature (150°C)
T_A = Free-ambient air temperature (°C)
θ_JA = θ_JC + θ_CA
θ_JC = Thermal coefficient from junction to case
θ_CA = Thermal coefficient from case to ambient air (°C/W)
MAXIMUM POWER DISSIPATION
vs
FREE-AIR TEMPERATURE
3.5
DGN Package
θ_JA = 58.4°C/W
TJ = 150°C
3
2 oz. Trace And Copper Pad
With Solder
2.5
SOIC Package
High-K Test PCB
2 ^θJA ^{= 98°C/W}
DGN Package
θ_JA = 158°C/W
2 oz. Trace And
Copper Pad
Without Solder
1.5
1
0.5 ^{SOIC Package}
Low-K Test PCB
θ_JA = 167°C/W
0
–40 –20 0 20 40 60 80 100
TA – Free-Air Temperature – °C
NOTE A: Results are with no air flow and PCB size = 3”× 3”
Figure 46. Maximum Power Dissipation vs Free-Air Temperature
More complete details of the PowerPAD installation process and thermal management techniques can be found
in the Texas Instruments Technical Brief, PowerPAD Thermally Enhanced Package. This document can be
found at the TI web site (www.ti.com) by searching on the key word PowerPAD. The document can also be
ordered through your local TI sales office. Refer to literature number SLMA002 when ordering.
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