Document Number: 70051
S10-1528-Rev. G, 19-Jul-10
www.vishay.com
9
Vishay Siliconix
DG417, DG418, DG419
TEST CIRCUITS
APPLICATIONS
Switched Signal Powers Analog Switch
The analog switch in Figure 10 derives power from its input
signal, provided the input signal amplitude exceeds 4 V and
its frequency exceeds 1 kHz.
This circuit is useful when signals have to be routed to either
of two remote loads. Only three conductors are required: one
for the signal to be switched, one for the control signal and a
common return.
A positive input pulse turns on the clamping diode D
1
and
charges C
1
. The charge stored on C
1
is used to power the
chip; operation is satisfactory because the switch requires
less than 1 µA of stand-by supply current. Loading of the
signal source is imperceptible. The DG419’s on-resistance is
a low 100 for a 5 V input signal.
Figure 9. Source/Drain Capacitances
V
L
IN
S
V+
D
f = 1 MHz
- 15 V
GND V-
C
0 V, 2.4 V
Meter
HP4192A
Impedance
Analyzer
or Equivalent
+ 5 V
C
+ 15 V
C
D
2
D
1
S
1
f = 1 MHz
+ 15 V
IN
S
2
NC
GND
V+
C
C
0 V, 2.4 V
Meter
HP4192A
Impedance
Analyzer
or Equivalent
DG417/418
DG419
V
L
IN
S
D
f = 1 MHz
GND
C
0 V, 2.4 V
CC
D
2
D
1
S
1
f = 1 MHz
IN
S
2
NC
- 15 V
GND
V+
V-
C
C
0 V, 2.4 V
Meter
HP4192A
Impedance
Analyzer
or Equivalent
Figure 10. Switched Signal Powers Remote SPDT Analog Switch
Input
Control
GND
DG419
V-
C
1
0.01 µF
D
1
S
1
S
2
V
OUT
R
L1
10 k
R
L2
10 k
V
L
D
IN
V+