Datasheet

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THERMAL ANALYSIS
DESIGN TOOLS
Evaluation Fixtures and Application Support
P
Dmax

T
max
–T
A

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).
4
3
2
0
−40 −20 0 20
− Maximum Power Dissipation − W
5
6
7
40 60 80
T
A
− Ambient Temperature − °C
P
D
16-Pin RGT Package
θ
JA
= 39.5°C/W for 16-Pin MSOP (RGT)
T
J
= 150°C, No Airflow
1
THS4303
SLOS421B – NOVEMBER 2003 – REVISED JANUARY 2005
important to consider not only quiescent power dissi-
pation, but also dynamic power dissipation. Often
maximum power is difficult to quantify because the
The THS4303 device does not incorporate automatic
signal pattern is inconsistent, but an estimate of the
thermal shutoff protection, so the designer must take
RMS power dissipation can provide visibility into a
care to ensure that the design does not violate the
possible problem.
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
,
Information
maximum power dissipation for a package can be
Texas Instruments is committed to providing its cus-
calculated using the following formula.
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
The THS4303 is offered in a 16-pin leadless MSOP
Computer simulation of circuit performance using
with PowerPAD. The thermal coefficient for the
SPICE is often useful when analyzing the perform-
MSOP PowerPAD package is substantially improved
ance of analog circuits and systems. This is particu-
over the traditional packages. Maximum power dissi-
larly true for video and RF amplifier circuits where
pation levels are depicted in the graph below. The
parasitic capacitance and inductance can have a
data for the RGT package assumes a board layout
major effect on circuit performance. A SPICE model
that follows the PowerPAD layout guidelines refer-
for the THS4303 device is available through the
enced above and detailed in the PowerPAD appli-
Texas Instruments web site at www.ti.com . The
cation notes in the Additional Reference Material
Product Information Center (PIC) is also available for
section at the end of the data sheet.
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.
Figure 50. Maximum Power Dissipation
vs
Ambient Temperature
When determining whether or not the device satisfies
the maximum power dissipation requirement, it is
20