THS3095_14 Datasheet, PDF (24/37 Pages) Texas Instruments – HIGH-VOLTAGE, LOW-DISTORTION, CURRENT-FEEDBACK OPERATIONAL AMPLIFIERS

THS3091
THS3095
SLOS423G – SEPTEMBER 2003 – REVISED OCTOBER 2008........................................................................................................................................ www.ti.com
complete connection around the entire
circumference of the plated-through hole.
6. The top-side solder mask should leave the
terminals of the package and the thermal pad
area with its 13 holes exposed. The bottom-side
solder mask should cover the 13 holes of the
thermal pad area. This prevents solder from
being pulled away from the thermal pad area
during the reflow process.
7. Apply solder paste to the exposed thermal pad
area and all of the IC terminals.
8. With these preparatory steps in place, the IC is
simply placed in position and run through the
solder reflow operation as any standard
surface-mount component. This results in a part
that is properly installed.
above and detailed in the PowerPAD application note
(SLMA002). The following graph also illustrates the
effect of not soldering the PowerPAD to a PCB. The
thermal impedance increases substantially which may
cause serious heat and performance issues. Be sure
to always solder the PowerPAD to the PCB for
optimum performance.
POWER DISSIPATION AND THERMAL
CONSIDERATIONS
The THS3091/5 incorporates automatic thermal
shutoff protection. This protection circuitry shuts down
the amplifier if the junction temperature exceeds
approximately 160°C. When the junction temperature
reduces to approximately 140°C, the amplifier turns
on again. But, for maximum performance and
reliability, the designer must ensure that the design
does not exceed a junction temperature of 125°C.
Between 125°C and 150°C, damage does not occur,
but the performance of the amplifier begins to
degrade and long-term reliability suffers. 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 *
q_JA
T_A
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 THS3091 and THS3095 are offered in an 8-pin
SOIC (DDA) with PowerPAD package. The thermal
coefficient for the PowerPAD packages are
substantially improved over the traditional SOIC.
Maximum power dissipation levels are depicted in the
graph for the available packages. The data for the
PowerPAD packages assume a board layout that
follows the PowerPAD layout guidelines referenced
Results are With No Air Flow and PCB Size =
3 inches x 3 inches (76,2 mm x 76,2 mm)
Figure 73. Maximum Power Distribution vs
Ambient Temperature
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
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.
DESIGN TOOLS
Evaluation Fixtures, Spice Models, and
Application Support
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 THS3091/5 operational
amplifier. The board is easy to use, allowing for
straightforward evaluation of the device. The
evaluation board can be ordered through the Texas
Instruments Web site, www.ti.com, or through your
local Texas Instruments sales representative.
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
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