CLC109/110/111 Evaluation Boards
Part Numbers CLC730012, CLC730045
August 1996
1996 National Semiconductor Corporation
http://www.national.com
Printed in the U.S.A.
N
The CLC730012 is an evaluation board intended for the
evaluation of single buffers in the DIP package. The
CLC730045 is a similar board, but laid out for an SOIC
package.
To obtain optimum performance from a high speed
device, a good Printed Circuit Board (PCB) layout is
essential. The importance of the layout becomes greater
as the frequency of operation increases. Some of
Comlinear's buffers have bandwidths in excess of 800
MHZ, therefore it is vital that sound PCB layout tech-
niques be used when designing with these devices. The
CLC730012 and CLC730045 are examples of good PCB
layouts which designers are encouraged to copy.
To minimize capacitive feedthrough and noise, the pins
not connected internally, should be connected to the
ground plane. Input and output traces should be laid out
as transmission lines with the appropriate termination
resistors very near the device. On a 0.0065" (FR4 or
equivalent) a 0.1" wide trace over ground plane on the
opposite side of the board will exhibit a characteristic
impedance of 50 .
Figure 1 shows recommended power supply bypassing.
The ferrite beads are optional and are recommended only
where additional isolation is needed from high-frequency
(>400MHz) resonances of the power supply.
Parasitic or load capacitance directly on the output of a
buffer will introduce additional phase shift in the device. If
excessive, this phase shift can lead to peaking in the fre-
quency response or, in extreme cases, oscillation. A
small series resistor in series with a capacitive load effec-
tively decouples it from the buffer output and removes the
undesirable effects of excess phase shift. Further detail
on the selection of these resistors can be found in the indi-
vidual buffer data sheets.
Parts List
R
IN
select for desired input resistance
R
OUT
select for desired output resistance
C
1
, C
2
0.1
F capacitor
C
3
, C
4
6.8
F capacitor
L
1
, L
2
Optional ferrite bead inductors
Figure 1: Recommended Circuit and
Evaluation Board Schematic
Figure 2: Component Placement Guide
http://www.national.com
2
Lit #660109-001
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Figure 3: 730012 Solder Side (bottom)
viewed from Component Side (top)
Figure 4: 730012 Component Side (top)
Showing Ground Plane
Figure 5: 730045 Solder Side (bottom)
viewed from Component Side (top)
Figure 6: 730045 Component Side (top)
Showing Ground Plane
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