DG417/418/419
Applications (Cont’d)
change of state in the analog switch, restoring normal
operation.
Micropower UPS Transfer Switch
When V
drops to 3.3 V, the DG417 changes states,
CC
Programmable Gain Amplifier
closing SW and connecting the backup cell, as shown in
1
Figure 11. D prevents current from leaking back towards
1
The DG419, as shown in Figure 12, allows accurate gain
selection in a small package. Switching into virtual ground
the rest of the circuit. Current consumption by the CMOS
analog switch is around 100 pA; this ensures that most of the
power available is applied to the memory, where it is really
needed. In the stand-by mode, hundreds of mA are sufficient
to retain memory data.
reduces distortion caused by r
of analog signal amplitude.
variation as a function
DS(on)
GaAs FET Driver
The DG419, as shown in Figure 13 may be used as a GaAs
When the 5-V supply comes back up, the resistor divider FET driver. It translates a TTL control signal into –8-V, 0-V
senses the presence of at least 3.5 V, and causes a new level outputs to drive the gate.
V+
V
L
D
SW
1
1
D
S
V
CC
(5 V)
+
–
R
V
1
Memory
DG417
SENSE
3 V Li Cell
453 kW
IN
GND
V–
R
2
383 kW
Figure 11. Micropower UPS Circuit
+5 V
V+
DG419
R
1
S
S
1
V
GaAs FET
L
R
2
2
S
S
1
IN
V
OUT
D
2
D
DG419
5 V
V
–
IN
GND
V–
V
OUT
+
–8 V
Figure 12. Programmable Gain Amplifier
Figure 13. GaAs FET Driver
10
Siliconix
S-52880—Rev. D, 28-Apr-97
TEMIC [ TEMIC SEMICONDUCTORS ]
