THS6042_16 Datasheet, PDF (24/46 Pages) Texas Instruments – 350mA,12V ADSL CPE LINE DRIVERS

THS6042, THS6043
350 mA, ±12 V ADSL CPE LINE DRIVERS
SLOS264G − MARCH 2000 − REVISED DECEMBER 2001
APPLICATION INFORMATION
PCB design considerations (continued)
6. Apply solder paste to the exposed thermal pad area and all of the operational amplifier terminals.
7. With these preparatory steps in place, the THS6042/3 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.
The actual thermal performance achieved with the THS6042/3 in their PowerPAD packages depends on the
application. In the previous example, if the size of the internal ground plane is approximately 3 inches × 3 inches,
then the expected thermal coefficient, θ_JA, is about 95°C/W for the SOIC−8 (D) package, 45.8°C/W for the DDA
package, 66.6°C/W for the SOIC−14 (D) package, and 37.5°C/W for the PWP package. Although the maximum
recommended junction temperature (T_J) is listed as 150°C, performance at this elevated temperature will suffer.
To ensure optimal performance, the junction temperature should be kept below 125°C. Above this temperature,
distortion will tend to increase. Figure 44 shows the recommended power dissipation with a junction
temperature of 125°C. If no solder is used to connect the PowerPAD to the PCB, the θ_JA will increase
dramatically with a vast reduction in power dissipation capability. For a given θ_JA and a maximum junction
temperature, the power dissipation is calculated by the following formula:
ǒ Ǔ PD +
TMAX–TA
q_JA
Where:
P_D = Power dissipation of THS6042/3 (watts)
T_MAX = Maximum junction temperature allowed in the design (125°C recommended)
T_A = Free-ambient air temperature (°C)
θ_JA = θ_JC + θ_CA
θ_JC = Thermal coefficient from junction to case (D−8 =38.3°C/W, DDA = 9.2°C/W,
D−14 = 26.9°C/W, PWP = 1.4°C/W)
θ_CA = Thermal coefficient from case to ambient
5
PWP
θ_JA = 37.5 °C/W
TJ = 125 °C
4
DDA
θ_JA = 45.8 °C/W
D-14
3
θ_JA = 66.6 °C/W
2
1
D-8
θ_JA = 95 °C/W
0
−40 −20 0 20 40 60 80 100
Ta − Free-Air Temperature − °C
NOTE: Results are with no air flow and PCB size = 3”× 3”
2 oz. trace and copper pad with solder unless otherwise noted.
Figure 44. Maximum Power Dissipation vs Free-Air Temperature
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