THS4051 Datasheet, PDF (22/30 Pages) Texas Instruments – 70-MHz HIGH-SPEED AMPLIFIERS

THS4051, THS4052
70-MHz HIGH-SPEED AMPLIFIERS
SLOS238C– MAY 1999 – REVISED MAY 2000
APPLICATION INFORMATION
general PowerPAD™ design considerations (continued)
The actual thermal performance achieved with the THS405xDGN 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 THS405x IC (SOIC) is shown. For a given θJA, the maximum power dissipation is shown in Figure 53 and}
is calculated by the following formula:
PD
TMAX–TA
q_JA
Where:
P_D = Maximum power dissipation of THS405x 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 53. 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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