THS3115CPWP Datasheet, PDF (17/35 Pages) Texas Instruments – LOW-NOISE, HIGH-SPEED, CURRENT FEEDBACK AMPLIFIERS

www.ti.com
PowerPAD™ Layout Considerations
Pin 1
0.205
(5,21)
0.060
(1,52)
0.013
(0,33)
0.017
(0,432)
0.075
(1,91)
0.030
(0,76)
0.010
(0,254)
vias
0.035
(0,89)
Top View
0.094
(2,39)
0.025
(0,64)
0.040
(1,01)
Dimensions are in inches (millimeters).
Figure 51. DGN PowerPAD PCB Etch and Via
Pattern
Although there are many ways to properly heatsink
the PowerPAD package, the following steps illustrate
the recommended approach.
1. PCB with a top side etch pattern as shown in
Figure 51.
2. Place five holes in the area of the thermal pad.
These holes should be 0.01 inch (0,254 mm) 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. These vias help dissipate the heat
generated by the THS3115/THS3112 IC. These
additional vias may be larger than the 0.01-inch
(0,254-mm) 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.
Note that the PowerPAD is electrically isolated
from the silicon and all leads. Connecting the
PowerPAD to any potential voltage, such as V_S–,
is acceptable as there is no electrical connection
to the silicon.
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 resistance makes the
soldering of vias that have plane connections
easier. In this application; however, low thermal
resistance is desired for the most efficient heat
THS3112
THS3115
SLOS385C – SEPTEMBER 2001 – REVISED SEPTEMBER 2010
transfer. Therefore, the holes under the
THS3115/THS3112 PowerPAD package should
make the 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 configuration 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 procedure results
in a part that is properly installed.
Power Dissipation and Thermal
Considerations
The THS3115 and THS3112 incorporate automatic
thermal shutoff protection. This protection circuitry
shuts down the amplifier if the junction temperature
exceeds approximately +160°C. When the junction
temperature reduces to approximately +140°C, the
amplifier turns on again. However, for maximum
performance and reliability, the designer must take
care to ensure that the design does not exceed a
junction temperature of +125°C. Between +125°C
and +150°C, damage does not occur, but the
performance of the amplifier begins to degrade and
long-term reliability suffers. The thermal
characteristics of the device are dictated by the
package and the PCB. Maximum power dissipation
for a given package can be calculated using the
following formula.
T -T
P_DMax =
max
q
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)
q_JA = q_JC + q_CA
where:
• q_JC is the thermal coefficient from the silicon
junctions to the case (°C/W)
• q_CA is the thermal coefficient from the case to
ambient air (°C/W)
Copyright © 2001–2010, Texas Instruments Incorporated
Product Folder Link(s): THS3112 THS3115
Submit Documentation Feedback
17