THS6012 Datasheet, PDF (27/35 Pages) Texas Instruments – 500-mA DUAL DIFFERENTIAL LINE DRIVER

THS6012
500-mA DUAL DIFFERENTIAL LINE DRIVER
SLOS226C– SEPTEMBER 1998 – REVISED FEBRUARY 2000
APPLICATION INFORMATION
PCB design considerations (continued)
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.
However, in this application, low thermal resistance is desired for the most efficient heat transfer. Therefore,
the holes under the THS6012 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 exposed the terminals of the package and the thermal pad area with
its five holes. The four larger holes outside the thermal pad area, but still under the package, should be
covered with solder mask.
7. Apply solder paste to the exposed thermal pad area and all of the operational amplifier terminals.
8. With these preparatory steps in place, the THS6012 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.
Addition 6 vias outside of thermal pad area
but under the package
(Via diameter = 25 mils)
Thermal pad area (0.19 x 0.21) with 18 vias
(Via diameter = 13 mils)
Figure 45. PowerPAD PCB Etch and Via Pattern
The actual thermal performance achieved with the THS6012 in its PowerPAD package depends on the
application. In the previous example, if the size of the internal ground plane is approximately 3 inches × 3 inches,
+ ǒ Ǔ ^{then the expected thermal coefficient, θJA, is about 21.5_C/W. For a given θJA, the maximum power dissipation}
is shown in Figure 46 and is calculated by the following formula:
PD
TMAX–TA
q_JA
Where:
P_D = Maximum power dissipation of THS6012 (watts)
T_MAX = Absolute maximum junction temperature (150°C)
T_A = Free-ambient air temperature (°C)
θ_JA = θ_JC + θ_CA
θ_JC = Thermal coefficient from junction to case (0.37°C/W)
θ_CA = Thermal coefficient from case to ambient
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