THS4031_16 Datasheet, PDF (31/47 Pages) Texas Instruments – THS403x 100-MHz Low-Noise High-Speed Amplifiers

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THS4031, THS4032
SLOS224H – JULY 1999 – REVISED JUNE 2016
General PowerPAD™ Design Considerations (continued)
• T_MAX = Absolute maximum operating junction temperature (125°C)
• T_A = Free-ambient air temperature (°C)
• R_θJA = R_θJC + R_θCA
– R_θJC = Thermal coefficient from junction to case
– R_θCA = Thermal coefficient from case to ambient air (°C/W)
(4)
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 (see PowerPAD™ Thermally-Enhanced Package when ordering)
The next thing to be considered is 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 multiamplifier 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. When using V_CC = ±5 V, heat is generally not a
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 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. 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, R_θJA decreases and the heat dissipation capability increases. For the dual amplifier package (THS4032),
the sum of the RMS output currents and voltages should be used to choose the proper package.
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