THS4042 Datasheet, PDF (20/34 Pages) National Semiconductor (TI) – 165-MHz C-STABLE HIGH-SPEED AMPLIFIER

THS4041, THS4042
ą
165ĆMHz CĆSTABLE HIGHĆSPEED AMPLIFIERS
SLOS237B− MAY 1999 − REVISED FEBRUARY 2000
APPLICATION INFORMATION
general PowerPAD design considerations (continued)
The actual thermal performance achieved with the THS404xDGN 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 of
the THS404x IC (SOIC) is shown. For a given θ_JA, the maximum power dissipation is shown in Figure 71 and
is calculated by the following formula:
Where:
ǒ Ǔ PD +
TMAX–TA
q_JA
P_D = Maximum power dissipation of THS404x 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 (°C/W)
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 71. 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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