Datasheet

OPA569
SBOS264A
18
www.ti.com
PARALLEL OPERATION
The OPA569 allows parallel operation of multiple op amps to
extend output current capability or improve the output volt-
age swing to the rail. Special internal circuitry causes the
load current to be shared equally between two (or more) op
amps.
Figure 14 shows two ways to connect the input terminals.
When the amplifier inputs are connected in parallel, the
effective offset voltage is averaged and the bandwidth and
slew rate performance are the same as that of a single
amplifier. It is also possible to use one amplifier to be the
“master” and connect the other inputs to a voltage within the
common-mode input range of the amplifier; however, slew
rate and bandwidth performance will be degraded.
For best performance, keep additional capacitance at the
Parallel Out pins to a minimum and avoid routing these lines
close to other lines that might see large voltage swings.
FIGURE 14. Parallel Operation.
Mold Compound (Epoxy)
Leadframe Die Pad
Exposed at Base of the Package
Leadframe (Copper Alloy)
IC (Silicon)
Die Attach (Epoxy)
FIGURE 15. Section View of a PowerPAD Package.
PowerPAD THERMALLY ENHANCED PACKAGE
The OPA569 uses the SO-20 PowerPAD package, a ther-
mally enhanced, standard size IC package designed to
eliminate the use of bulky heatsinks and slugs traditionally
used in thermal packages. This package can be easily
mounted using standard PCB assembly techniques.
The PowerPAD package is designed so that the leadframe
die pad (or thermal pad) is exposed on the bottom of the IC,
as shown in Figure 15. This provides an extremely low
thermal resistance (
θ
JC
) path between the die and the
exterior of the package. The thermal pad on the bottom of
the IC can then be soldered directly to the PCB, using the
PCB as a heatsink. In addition, plated-through holes (vias)
provide a low thermal resistance heat flow path to the back
side of the PCB.
Soldering the PowerPAD to the PCB ia always recom-
mended, even with applications that have low power dissipa-
tion. This provides the necessary thermal and mechanical
connection between the leadframe die pad and the PCB.
OPA569
(A2)
V+
V
IN
V–
(a) Inputs connected in parallel.
17,
18
12,
13
5
6
2
9
14,
15
R
L
Parallel Out 2
Parallel Out 1
OPA569
(A1)
V+
V–
17,
18
12,
13
5
6
2
9
14,
15
Parallel Out 2
Parallel Out 1
OPA569
(A2)
V+
V
IN
V–
(b) Amplifier A1 as “master”, A2 as “slave”.
17,
18
12,
13
5
6
2
9
14,
15
R
L
Parallel Out 2
Parallel Out 1
OPA569
(A1)
V+
V–
17,
18
12,
13
5
6
2
9
14,
15
Parallel Out 2
Parallel Out 1
PowerPAD Assembly Process
1. The PowerPAD must be connected to the most negative
supply voltage of the device, which will be ground in single-
supply applications and V– in split-supply applications.
2. Prepare the PCB with a top-side etch pattern, as shown in
Figure 16. There should be etch for the leads as well as
etch for the thermal land.
3. Place the recommended number of plated-through holes
(or thermal vias) in the area of the thermal pad. These
holes should be 13 mils in diameter. They are kept small
so that solder wicking through the holes is not a problem
during reflow. The minimum recommended number of
holes for the SO-20 PowerPAD package is 24, as shown
in Figure 16.
4. It is recommended, but not required, to place a small
number of additional holes under the package and outside
the thermal pad area. These holes provide an additional
heat path between the copper land and the ground plane.
They may be larger because they are not in the area to be
soldered, so wicking is not a problem. This is illustrated in
Figure 16.