THS4601_14 Datasheet, PDF (21/32 Pages) Texas Instruments – WIDEBAND, FET-INPUT OPERATIONAL AMPLIFIER

THS4601
SLOS388B − OCTOBER 2001 − REVISED JUNE 2002
APPLICATION INFORMATION
power dissipation and thermal characteristics
The THS4601 does not incorporate automatic thermal shutoff protection, so the designer must take care to
ensure that the design does not violate the absolute maximum junction temperature of the device. Failure may
result if the absolute maximum junction temperature of 150°C is exceeded.
The thermal characteristics of the device are dictated by the package and the PC board. Maximum power
dissipation for a given package can be calculated using the following formula.
P_Dmax
+
Tmax–TA
q_JA
Where:
P_Dmax is the maximum power dissipation (W)
T_max is the absolute maximum junction temperature (°C)
T_A is the ambient temperature (°C)
θ_JA is the thermal coefficient from the silicon junctions to the ambient air (°C/W)
For systems where heat dissipation is more critical, the THS4601 is offered in an 8-pin SOIC with PowerPAD.
The thermal coefficient for the SOIC PowerPAD is substantially improved over the traditional SOIC. Maximum
power dissipation levels are depicted in the graph for the two packages. The data for the 8DDA package
assumes a board layout that follows the PowerPAD layout guidelines.
MAXIMUM POWER DISSIPATION
vs
TEMPERATURE
3
θ_JA = 170°C/W for 8D,
2.5
θ_JA = 66.6°C/W for 8DDA
2
8DDA Package
1.5
1
8D Package
0.5
0
−40 −20 0 20 40 60 80
Ambient Temperature − °C
Figure 40
When determining whether or not the device satisfies the maximum power dissipation requirement, it is
important to not only consider quiescent power dissipation, but also dynamic power dissipation. Often times,
this is difficult to quantify because the signal pattern is inconsistent, but an estimate of the RMS power
dissipation can provide visibility into a possible problem.
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