THS3201 Datasheet, PDF (20/29 Pages) Texas Instruments – 1.8-GHz, LOW DISTORTION, CURRENT FEEDBACK AMPLIFIER

THS3201
SLOS416A − JUNE 2003 − REVISED JANUARY 2004
PowerPAD PCB LAYOUT CONSIDERATIONS
1. Prepare the PCB with a top side etch pattern as shown
in Figure 62. There should be etch for the leads as well
as etch for the thermal pad.
2. Place five holes in the area of the thermal pad. These
holes should be 10 mils in diameter. Keep them small
so that solder wicking through the holes is not a
problem during reflow.
3. Additional vias may be placed anywhere along the
thermal plane outside of the thermal pad area. This
helps dissipate the heat generated by the THS3201
IC. These additional vias may be larger than the 10-mil
diameter vias directly under the thermal pad. They can
be larger because they are not in the thermal pad area
to be soldered so that wicking is not a problem.
4. Connect all holes to the internal ground plane.
5. When connecting these holes to the ground plane, do
not use the typical web or spoke via connection
methodology. Web connections have a high thermal
resistance connection that is useful for slowing the
heat transfer during soldering operations. This makes
the soldering of vias that have plane connections
easier. In this application, however, low thermal
resistance is desired for the most efficient heat
transfer. Therefore, the holes under the THS3201
PowerPAD package should make their connection to
the internal ground plane with a 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 five
holes exposed. The bottom-side solder mask should
cover the five holes of the thermal pad area. This
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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.
POWER DISSIPATION AND THERMAL
CONSIDERATIONS
To maintain maximum output capabilities, the THS3201
does not incorporate automatic thermal shutoff protection.
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. 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 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).
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