P
Dmax +
Tmax–TA
q
JA
where
PDmax is the maximum power dissipation in the amplifier (W).
Tmax is the absolute maximum junction temperature (°C).
TA is the ambient temperature (°C).
θJA = θJC + θCA
θJC is the thermal coefficient from the silicon junctions to the
case (
°C/W).
θCA is the thermal coefficient from the case to ambient air
(
°C/W).
-4
-2
10
12
10 M
100 M
1 G
f - Frequency - Hz
Normalized
Gain
-
dB
0
8
6
4
2
SOIC, Rf = 0
PIN = -7 dB
VS =±5 V
Leadless MSOP, &
MSOP Rf = 0
SOIC, Rf = 100
_
+
Rf
49.9
499
2
1.5
1
0
-40
-20
0
20
-Maximum
Power
Dissipation
-
W
2.5
3
3.5
40
60
80
TA - Ambient Temperature - °C
P
D
8-Pin DGN Package
θJA = 170°C/W for 8-Pin SOIC (D)
θJA = 58.4°C/W for 8-Pin MSOP (DGN)
TJ= 150°C, No Airflow
0.5
8-Pin D Package
www.ti.com ................................................................................................................................... SLOS400E – SEPTEMBER 2002 – REVISED SEPTEMBER 2009
THERMAL ANALYSIS
When determining whether or not the device satisfies
the maximum power dissipation requirement, it is
The THS4211 device does not incorporate automatic
important to consider not only quiescent power
thermal shutoff protection, so the designer must take
dissipation, but also dynamic power dissipation. Often
care to ensure that the design does not violate the
maximum power dissipation is difficult to quantify
absolute
maximum
junction
temperature
of
the
because the signal pattern is inconsistent, but an
device. Failure may result if the absolute maximum
estimate of the RMS power dissipation can provide
junction temperature of 150°C is exceeded.
visibility into a possible problem.
The thermal characteristics of the device are dictated
by the package and the PCB. Maximum power
DESIGN TOOLS
dissipation for a given package can be calculated
Performance vs Package Options
The THS4211 and THS4215 are offered in a different
package options. However, performance may be
limited due to package parasitics and lead inductance
in some packages. In order to achieve maximum
performance of the THS4211 and THS4215, Texas
Instruments recommends using the leadless MSOP
(DRB) or MSOP (DGN) packages, in addition to
proper high-speed PCB layout.
Figure 92 shows the
unity-gain frequency response of the THS4211 using
the leadless MSOP, MSOP, and SOIC package for
comparison. Using the THS4211 and THS4215 in a
(7)
unity-gain with the SOIC package may result in the
For systems where heat dissipation is more critical,
device
becoming
unstable.
In
higher
gain
the THS4211 is offered in an 8-pin MSOP with
configurations, this effect is mitigated by the reduced
PowerPAD. The thermal coefficient for the MSOP
bandwidth. As such, the SOIC is suitable for
PowerPAD package is substantially improved over
application with gains equal to or higher than +2 V/V
the traditional SOIC. Maximum power dissipation
or (–1 V/V).
levels are depicted in the graph for the two packages.
The data for the DGN package assumes a board
layout that follows the PowerPAD layout guidelines
referenced above and detailed in the PowerPAD
section at the end of the data sheet.
Figure 92. Effects of Unity-Gain Frequency
Response for Differential Packages
Figure 91. Maximum Power Dissipation vs
Ambient Temperature
Copyright 2002–2009, Texas Instruments Incorporated
29