THS3061_16 Datasheet, PDF (17/33 Pages) Texas Instruments – LOW-DISTORTION, HIGH SLEW RATE, CURRENT-FEEDBACK AMPLIFIERS

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solder reflow operation as any standard
surface-mount component. This results in a
properly-installed device.
POWER DISSIPATION AND
THERMAL CONSIDERATIONS
To maintain maximum output capability, the THS360x
does not incorporate automatic thermal shutoff
protection. The designer must 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. For best performance, design for a
maximum junction temperature of +125°C. Between
+125°C and +150°C, damage does not occur, but the
performance of the amplifier begins to degrade.
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 Equation 1.
P _Dmax
+
T_max *
q
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).
(1)
For systems where heat dissipation is more critical,
the THS306x family of devices is offered in an 8-pin
MSOP with PowerPAD, and the THS3062 is available
in the SOIC-8 PowerPAD package offering even
better thermal performance. The thermal coefficients
for the PowerPAD packages are substantially
improved over traditional SOICs. Maximum power
dissipation levels are given in the graph for the
available packages. Data for the PowerPAD
packages assumes a board layout that follows the
PowerPAD layout guidelines referenced above and
detailed in the PowerPAD application note number
SLMA002. The following graph also illustrates the
effect of not soldering the PowerPAD to a PCB. The
thermal impedance increases substantially, which can
cause serious heat and performance issues. Always
be sure to solder the PowerPAD to the PCB for
optimum performance.
THS3061
THS3062
SLOS394B – JULY 2002 – REVISED NOVEMBER 2009
4
T_J = 125°C
3.5
θ_JA = 45.8°C/W
3
θ_JA = 58.4°C/W
2.5
θ_JA = 98°C/W
2
1.5
1
0.5
θ_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”x3”
θ_JA = 45.8°C/W for 8-Pin SOIC w/PowerPad (DDA)
θ_JA = 58.4°C/W for 8-Pin MSOP w/PowerPad (DGN)
θ_JA = 98°C/W for 8-Pin SOIC High Test PCB (D)
θ_JA = 158°C/W for 8-Pin MSOP w/PowerPad w/o Solder
Figure 52. Maximum Power Dissipation
vs Ambient Temperature
When determining whether or not the device satisfies
the maximum power dissipation requirement, it is
important not only to consider quiescent power
dissipation, but also dynamic power dissipation.
Often, 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.
DRIVING A CAPACITIVE LOAD
Driving capacitive loads with high-performance
amplifiers is not a problem as long as certain
precautions are taken. The first is to realize that the
THS306x has been internally compensated to
maximize its bandwidth and slew-rate performance.
When the amplifier is compensated in this manner,
capacitive loading directly on the output decreases
the device's phase margin, leading to high-frequency
ringing or oscillations. Therefore, for capacitive loads
of greater than 10 pF, it is recommended that a
resistor be placed in series with the output of the
amplifier as shown in Figure 53. A minimum value of
10 Ω works well for most applications. For example,
in 75-Ω transmission systems, setting the
series-resistor value to 75 Ω both isolates any
capacitive loading and provides the proper line
impedance matching at the source end.
Copyright © 2002–2009, Texas Instruments Incorporated
Product Folder Link(s): THS3061 THS3062
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