THS4011_16 Datasheet, PDF (19/35 Pages) Texas Instruments – 290-MHz LOW-DISTORTION HIGH-SPEED AMPLIFIERS

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THS4011
THS4012
SLOS216E – JUNE 1999 – REVISED APRIL 2010
ǒ Ǔ PD +
TMAX * TA
q_JA
Where:
P_D = Maximum power dissipation of THS401x IC (watts)
T_MAX = Absolute maximum junction temperature (150°C)
T_A = Free-ambient air temperature (°C)
q_JA = q_JC + q_CA
q_JC = Thermal coefficient from junction to case
q_CA = Thermal coefficient from case to ambient air (°C/W)
3.5
DGN Package
θ_JA = 58.4°C/W
T_J = 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
T_A − Free-Air Temperature − °C
A. Results are with no airflow and PCB size = 3 in × 3 in
Figure 35. Maximum Power Dissipation vs Free-Air Temperature
More complete details of the PowerPAD installation process and thermal-management techniques can be found
in the TI technical brief, PowerPAD™ Thermally-Enhanced Package. This document can be found at the TI web
site (www.ti.com) by searching on the keyword PowerPAD. The document can also be ordered through your
local TI sales office. Refer to literature number SLMA002 when ordering.
The next consideration is the package constraints. The two sources of heat within an amplifier are quiescent
power and output power. The designer should never forget about the quiescent heat generated within the device,
especially multiple amplifier devices. Because these devices have linear output stages (Class A-B), most of the
heat dissipation is at low output voltages with high output currents. Figure 36 to Figure 39 show this effect, along
with the quiescent heat, with an ambient air temperature of 50°C. When using V_CC = ±5 V, there is generally not
a heat problem, even with SOIC packages. But, when using V_CC = ±15 V, the SOIC package is severely limited
in the amount of heat it can dissipate. The other key factor when looking at these graphs is how the devices are
mounted on the PCB. The PowerPAD devices are extremely useful for heat dissipation. But, the device should
always be soldered to a copper plane to fully use the heat-dissipation properties of the PowerPAD package. The
SOIC package, on the other hand, is highly dependent on how it is mounted on the PCB. As more trace and
copper area is placed around the device, q_JA decreases and the heat dissipation capability increases. The
currents and voltages shown in these graphs are for the total package. For the dual amplifier package
(THS4012), the sum of the RMS output currents and voltages should be used to choose the proper package.
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