BUF11702 Datasheet, PDF (19/24 Pages) Burr-Brown (TI) – MULTI CHANNEL LCD GAMMA CORRECTION BUFFER

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BUF11702
BUF07702
SLOS359F − MARCH 2001 − REVISED MAY 2004
DIE
Side View (a)
Thermal
Pad
DIE
End View (b)
Bottom View (c)
NOTE A: The thermal pad is electrically isolated from all terminals in the package.
Figure 51. Views of Thermally Enhanced DGN Package
PowerPAD ASSEMBLY PROCESS
1. Prepare the PCB with a top-side etch pattern (see
Pin Configurations). There should be etching for the
leads as well as etch for the thermal pad.
2. Place 18 holes in the area of the thermal pad. These
holes should be 13mils 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
BUFxx702 IC. These additional vias may be larger
than the 13mil diameter vias directly under the
thermal pad. They can be larger because they are
not in the thermal pad area to be soldered, thus,
wicking is not a problem.
4. Connect all holes to the internal ground plane.
8. With these preparatory steps in place, the
BUFxx702 IC is simply placed in position and run
through the solder reflow operation as any standard
surface-mount component. This preparation results
in a properly installed part.
For a given q_JA, the maximum power dissipation is
shown in Figure 52, and is calculated by the following
formula:
ǒ Ǔ P_D +
T_MAX * T_A
q_JA
Where:
P_D = maximum power dissipation (W)
T_MAX = absolute maximum junction temperature (150°C)
T_A = free-ambient air temperature (°C)
q_JA = q_JC + q_CA
q_JC = thermal coefficient from junction to case (°C/W)
q_CA = thermal coefficient from case-to-ambient air (°C/W)
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
BUFxx702 PowerPAD package should make their
connection to the internal ground plane with a
complete connection around the entire
circumference of the plated-through hole.
8
7
BUF11702
6
θ_JA = 27.9°C/W
2 oz. Trace and Copper
Pad With Solder
5
TJ = 125°C
4
3
2
1
6. The top-side solder mask should leave the terminals
of the package and the thermal pad area with its five
holes (dual) or nine holes (quad) exposed. The
bottom-side solder mask should cover the five or
nine 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.
0
−40 −20 0
20 40 60 80 100
TA − Free-Air Temperature − °C
Figure 52. Maximum Power Dissipation vs
Free-Air Temperature
This lower thermal resistance enables the
BUFxx702 to deliver maximum output currents
even at high ambient temperatures.
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