THS3061 Datasheet, PDF (18/25 Pages) Texas Instruments – LOW DISTORTION HIGH SLEW RATE CURRENT FREEBACK AMPLIFIERS

THS3061
THS3062
SLOS394A – JULY 2002 – OCTOBER 2002
www.ti.com
PowerPAD PCB LAYOUT CONSIDERATIONS
1. Prepare the PCB with a top side etch pattern as shown in Figure 51. 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 THS306x family 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 THS306x family 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 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 THS360x 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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