THS4302_14 Datasheet, PDF (18/28 Pages) Texas Instruments – WIDEBAND FIXED-GAIN AMPLIFIER

THS4302
SLOS403H – OCTOBER 2002 – REVISED AUGUST 2006
THERMAL ANALYSIS
The THS4302 device 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. For a given Θ_JA,
maximum power dissipation for a package can be
calculated using the following formula.
P _Dmax
+
T_max–T_A
q
JA
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).
(1)
The THS4302 is offered in a 16-pin leadless MSOP
with PowerPAD. The thermal coefficient for the
MSOP PowerPAD package is substantially improved
over the traditional packages. Maximum power
dissipation levels are depicted in the graph below.
The data for the RGT package assumes a board
layout that follows the PowerPAD layout guidelines
referenced above and detailed in the PowerPAD
application notes in the Additional Reference Material
section at the end of the data sheet.
7
6
16-Pin RGT Package
5
4
3
2
1
0
-40 -20
0
20 40 60 80
T_A - Ambient Temperature - °C
θ_JA = 39.5°C/W for 16-Pin MSOP (RGT)
T_J = 150°C, No Airflow
Figure 51. Maximum Power Dissipation vs
Ambient Temperature
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When determining whether or not the device satisfies
the maximum power dissipation requirement, it is
important to consider not only quiescent power
dissipation, but also dynamic power dissipation. Often
maximum power 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.
DESIGN TOOLS
Evaluation Fixtures and Application Support
Information
Texas Instruments is committed to providing its
customers with the highest quality of applications
support. To support this goal, an evaluation board
has been developed for the THS4302 operational
amplifier. The evaluation board is available and easy
to use allowing for straight-forward evaluation of the
device. This evaluation board can be obtained by
ordering through the Texas Instruments Web site,
www.ti.com, or through your local Texas Instruments
Sales Representative. A schematic for the evaluation
board with default component values is shown in
Figure 52. Unpopulated footprints are shown to
provide insight into design flexibility
Computer simulation of circuit performance using
SPICE is often useful when analyzing the
performance of analog circuits and systems. This is
particularly true for video and RF amplifier circuits
where parasitic capacitance and inductance can have
a major effect on circuit performance. A SPICE model
for the THS4500 family of devices is available
through the Texas Instruments web site (www.ti.com).
The Product Information Center (PIC) is available for
design assistance and detailed product information.
These models do a good job of predicting small
signal ac and transient performance under a wide
variety of operating conditions. They are not intended
to model the distortion characteristics of the amplifier,
nor do they attempt to distinguish between the
package types in their small signal ac performance.
Detailed information about what is and is not modeled
is contained in the model file itself.
18
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