THS4211 Datasheet, PDF (29/50 Pages) Texas Instruments – LOW-DISTORTION HIGH-SPEED VOLTAGE FEEDBACK AMPLIFIER

THS4211
THS4215
www.ti.com ................................................................................................................................... SLOS400E – SEPTEMBER 2002 – REVISED SEPTEMBER 2009
THERMAL ANALYSIS
The THS4211 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
device. 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 PCB. Maximum power
dissipation for a given package can be calculated
using Equation 7:
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).
(7)
For systems where heat dissipation is more critical,
the THS4211 is offered in an 8-pin MSOP with
PowerPAD. The thermal coefficient for the MSOP
PowerPAD package is substantially improved over
the traditional SOIC. Maximum power dissipation
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
application notes in the Additional Reference Material
section at the end of the data sheet.
3.5
8-Pin DGN Package
3
2.5
2
8-Pin D Package
1.5
1
0.5
0
-40 -20
0
20 40 60 80
T_A - Ambient Temperature - °C
θ_JA = 170°C/W for 8-Pin SOIC (D)
θ_JA = 58.4°C/W for 8-Pin MSOP (DGN)
T_J= 150°C, No Airflow
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
maximum power dissipation 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
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
unity-gain with the SOIC package may result in the
device becoming unstable. In higher gain
configurations, this effect is mitigated by the reduced
bandwidth. As such, the SOIC is suitable for
application with gains equal to or higher than +2 V/V
or (–1 V/V).
12
_ ^Rf
SOIC, R_f = 0 Ω
10
+
499 Ω
8
49.9 Ω
6
4
SOIC, R_f = 100 Ω
2
0
-2 P_IN = -7 dB
V_S =±5 V
-4
10 M
Leadless MSOP, &
MSOP R_f = 0 Ω
100 M
1G
f - Frequency - Hz
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
Product Folder Link(s): THS4211 THS4215
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