DG611_08 Datasheet, PDF (8/10 Pages) Vishay Siliconix – High-Speed, Low-Glitch D/CMOS Analog Switches

DG611/612/613
Vishay Siliconix
TEST CIRCUITS
+5V
+ 15 V
R_g
V_L
S
V+
D
V_g
IN
5V
GND
V-
V_O
C_L
1 nF
-3V
Figure 3. Charge Injection
+5V
C
+ 15 V
C
V_L
V+
V_S
S₁
D₁
R_g = 50 Ω
IN₁
1 V, 4 V
S₂
D₂
NC
1 V, 4 V
IN₂
GND
V-
C
X_{TA LK} Isolation = 20 log
C = RF bypass
V_S
V_O
-3V
Figure 4. Crosstalk
50 Ω
V_O
R_L
APPLICATIONS
High-Speed Sample-and-Hold
In a fast sample-and-hold application, the analog switch
characteristics are critical. A fast switch reduces aperture
uncertainty. A low charge injection eliminates offset (step)
errors. A low leakage reduces droop errors. The CLC111, a
fast input buffer, helps to shorten acquisition and settling
times. A low leakage, low dielectric absorption hold capacitor
must be used. Polycarbonate, polystyrene and
polypropylene are good choices. The JFET output buffer
reduces droop due to its low input bias current.
(See Figure 5.)
Pixel-Rate Switch
Windows, picture-in-picture, title overlays are economically
generated using a high-speed analog switch such as the
DG613. For this application the two video sources must be
sync locked. The glitch-less analog switch eliminates halos.
(See Figure 6.)
GaAs FET Drivers
Figure 7 illustrates a high-speed GaAs FET driver. To turn
the GaAs FET on 0 V are applied to its gate via S₁, whereas
to turn it off, - 8 V are applied via S₂. This high-speed,
low-power driver is especially suited for applications that
require a large number of RF switches, such as phased array
radars.
Analog
Input
Input Buffer
75 Ω
CLC111
5 V Control
+ 5 V + 12 V
S
D
IN
1_{/4 DG611}
Output Buffer
+
LF356
-
C_HOLD
650 pF Polystyrene
-5V
Figure 5. High-Speed Sample-and-Hold
± 5 V Output
to A/D
www.vishay.com
8
Document Number: 70057
S-71155–Rev. H, 11-Jun-07