THS4505 Datasheet, PDF (31/38 Pages) Texas Instruments – WIDEBAND, LOW-DISTORTION, FULLY DIFFERENTIAL AMPLIFIERS

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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
+
T_max–T_A
q_JA
(28)
Where:
P_Dmax is the maximum power dissipation in the amplifier (W).
T_max is the absolute maximum junction temperature (°C).
T_A is the ambient temperature (°C).
θ_JA = θ_JC + θ_CA
θ_JC is the thermal coefficient from the silicon junctions to the
case (°C/W).
θ_CA is the thermal coefficient from the case to ambient air
(°C/W).
For systems where heat dissipation is more critical,
the THS4500 family of devices is offered in an 8-pin
MSOP with PowerPAD. The thermal coefficient for
the MSOP PowerPAD package is substantially im-
proved over the traditional SOIC. Maximum power
dissipation levels are depicted in the graph for the
two packages. The data for the DGN package as-
sumes a board layout that follows the PowerPAD
layout guidelines referenced above and detailed in
the PowerPAD application notes in the Additional
Reference Materialsection at the end of the data
sheet.
THS4504
THS4505
SLOS363C – AUGUST 2002 – REVISED MARCH 2004
3.5
8-Pin DGN Package
3
2.5
2
8-Pin D Package
1.5
1
0.5
0
−40 −20 0
20 40 60 80
T_A − Ambient Temperature − °C
θ_JA = 170°C/W for 8-Pin SOIC (D)
θ_JA = 58.4°C/W for 8-Pin MSOP (DGN)
Τ_J = 150°C, No Airflow
Figure 95. Maximum Power Dissipation
vs Ambient Temperature
When determining whether or not the device satisfies
the maximum power dissipation requirement, it is
important to not only consider quiescent power dissi-
pation, 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.
31