Datasheet

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SBOS206E − DECEMBER 2001 − REVISED FEBRUARY 2007
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11
6. The top-side solder mask should leave exposed the
terminals of the package and the thermal pad area.
The thermal pad area should leave the 13 mil holes
exposed. The larger 25 mil holes outside the thermal
pad area should be covered with solder mask.
7. Apply solder paste to the exposed thermal pad area
and all of the package terminals.
8. With these preparatory steps in place, the PowerPAD
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.
For detailed information on the PowerPAD package
including thermal modeling considerations and repair
procedures, please see Technical Brief SLMA002,
PowerPAD Thermally Enhanced Package, available at
www.ti.com.
LAYOUT GUIDELINES
The OPA561 is a high-speed power amplifier that requires
proper layout for best performance. Figure 8 shows an
example of proper layout.
Pin 1
+V
IN
V
OUT
V+
V
−
−
V
IN
I
LIM
E/S
Figure 8. OPA561 Example Layout
Keep power-supply leads as short as possible. This will
keep inductance low and resistive losses at a minimum. A
minimum 18 gauge wire thickness is recommended for
power-supply leads. The wire length should be < 8 inches.
Proper power-supply bypassing with low ESR capacitors
is essential to achieve good performance. A parallel
combination of small ceramic (around 100nF) and bigger
(47µF) non-ceramic bypass capacitors will provide low
impedance over a wide frequency range. Bypass
capacitors should be placed as close as practical to the
power-supply pins of the OPA561.
PCB traces conducting high currents, such as from output
to load or from the power-supply connector to the
power-supply pins of the OPA561 should be kept as wide
and as short as possible. This will keep inductance low and
also resistive losses to a minimum.
The holes in the landing pattern for the OPA561 are for the
thermal vias that connect the PowerPAD of the OPA561 to
the heatsink area on the printed circuit board (see attached
Land Pattern mechanical drawing). The additional larger
vias further enhance the heat conduction into the heatsink
area. All traces conducting high currents are very wide for
lowest inductance and minimal resistive losses. Note that
the negative supply (V−) pin on the OPA561 is connected
through the PowerPAD. This allows for maximum trace
width for V
OUT
and the positive power supply (V+).