THS3120_16 Datasheet, PDF (22/35 Pages) Texas Instruments – LOW-NOISE, HIGH-OUTPUT DRIVE, CURRENT-FEEDBACK OPERATIONAL AMPLIFIERS

THS3120
THS3121
SLOS420E – SEPTEMBER 2003 – REVISED OCTOBER 2009........................................................................................................................................ www.ti.com
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.
POWER DISSIPATION AND THERMAL
CONSIDERATIONS
The THS3120 and THS3121 incorporate 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 take
care to 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 coeffiecient from the silicon junctions to
the case (°C/W).
θ_CA is the thermal coeffiecient from the case to ambient
air (°C/W).
(1)
For systems where heat dissipation is more critical,
the THS3120 and THS3121 are offered in an
MSOP-8 with PowerPAD package offering even
better thermal performance. 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 above and
detailed in the PowerPAD application note (literature
number SLMA002). 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.
4.0
T_J = +125°C
3.5
3.0
q_JA = 58.4°C/W
2.5
2.0
q_JA = 95°C/W
1.5
1.0
0.5
q_JA = 158°C/W
0
-40 -20 0 20 40 60 80 100
T_A - Free-Air Temperature - °C
Results are with no air flow and PCB size = 3 inches × 3 inches
(76,2 mm × 76,2 mm); θ_JA = 58.4°C/W for MSOP-8 with
PowerPAD (DGN); θ_JA = 95°C/W for SOIC-8 High-K test PCB (D);
θ_JA = 158°C/W for MSOP-8 with PowerPAD without solder.
Figure 61. Maximum Power Distribution 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
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 THS3120 and THS3121
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
where parasitic capacitance and inductance can have
a major effect on circuit performance. A SPICE model
for the THS3121 is available through the Texas
Instruments web site (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
22
Submit Documentation Feedback
Copyright © 2003–2009, Texas Instruments Incorporated
Product Folder Link(s): THS3120 THS3121