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| DG641_11 Datasheet, PDF (9/18 Pages) Vishay Siliconix – Low On-Resistance Wideband/Video Switches | |||
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APPLICATIONS
+ 15 V
+
C1
C2
V+
S1
S2
DG64X
S3
S4
V-
GNDs
C1
C2
C1 = 10 µF Tantalum
+
C2 = 0.1 µF Ceramic
-3V
Figure 7. Supply Decoupling
CH1
75 ï
CH2
75 ï
CH3
CH4
75 ï
75 ï
DG641, DG642, DG643
Vishay Siliconix
Board Layout
PCB layout rules for good high frequency performance must
also be observed to achieve the performance boasted by
these analog switches. Some tips for minimizing stray effects
are:
1. Use extensive ground planes on double sided PCB,
D1
D2
separating adjacent signal paths. Multilayer PCB is
D3
even better.
D4
2. Keep signal paths as short as practically possible,
with all channel paths of near equal length.
3. Careful arrangement of ground connections is also
very important. Star connected system grounds
eliminate signal current, flowing through ground path
parasitic resistance, from coupling between
channels.
Figure 8 shows a 4-channel video multiplexer using a
DG641.
In Figure 9, two coax cables terminated on 75 ï bring two
video signals to the DG642 switch. The two drains tied
together lower the on-state capacitance. An Si582 video
amplifier drives a double terminated 75 ï cable. The double
terminated coax cable eliminates line reflections.
+ 15 V
V+
DG641
V-
Si582
+
A=2
-
DIS
250 ï
250 ï
75 ï
-3V
TTL Channel Select
Figure 8. 4 by 1 Video Multiplexing Using the DG641
Document Number: 70058
S11-0154-Rev. F, 31-Jan-11
www.vishay.com
9
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