DG418 Datasheet, PDF (10/10 Pages) TEMIC Semiconductors – Precision CMOS Analog Switches

DG417/418/419
Applications (Cont’d)
Micropower UPS Transfer Switch
change of state in the analog switch, restoring normal
operation.
When V_CC drops to 3.3 V, the DG417 changes states,
closing SW₁ and connecting the backup cell, as shown in
Figure 11. D₁ prevents current from leaking back towards
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.
Programmable Gain Amplifier
The DG419, as shown in Figure 12, allows accurate gain
selection in a small package. Switching into virtual ground
reduces distortion caused by r_DS(on) variation as a function
of analog signal amplitude.
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_CC
(5 V)
D₁
R₁
V_SENSE
453 kW
Memory
R₂
383 kW
V+ _SW1 V_L
D
S
DG417
IN
GND
V–
+
3 V Li Cell
–
Figure 11. Micropower UPS Circuit
DG419
S₁
R₁
S₂
R₂
IN
D
V_IN
–
+
5V
V_OUT
+5 V
V_L
S₁
S₂
V+
GaAs FET
D ^VOUT
GND
DG419
V–
Figure 12. Programmable Gain Amplifier
10
–8 V
Figure 13. GaAs FET Driver
Siliconix
S-52880—Rev. D, 28-Apr-97