THS4303 Datasheet, PDF (20/24 Pages) Texas Instruments – WIDEBAND FIXED-GAIN AMPLIFIER

THS4303
SLOS421B – NOVEMBER 2003 – REVISED JANUARY 2005
THERMAL ANALYSIS
The THS4303 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 de-
vice. 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).
The THS4303 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 dissi-
pation levels are depicted in the graph below. The
data for the RGT package assumes a board layout
that follows the PowerPAD layout guidelines refer-
enced above and detailed in the PowerPAD appli-
cation 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 50. Maximum Power Dissipation
vs
Ambient Temperature
When determining whether or not the device satisfies
the maximum power dissipation requirement, it is
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important to consider not only quiescent power dissi-
pation, 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 cus-
tomers with the highest quality of applications sup-
port. To support this goal, an evaluation board has
been developed for the THS4303 operational ampli-
fier. The evaluation board is available and easy to
use allowing for straight-forward evaluation of the
device. These 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 is shown in Figure 51 with their default
component values. Unpopulated footprints are shown
to provide insight into design flexibility
Computer simulation of circuit performance using
SPICE is often useful when analyzing the perform-
ance of analog circuits and systems. This is particu-
larly 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 THS4303 device is available through the
Texas Instruments web site at www.ti.com. The
Product Information Center (PIC) is also 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 perform-
ance. Detailed information about what is and is not
modeled is contained in the model file itself.
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