DG419 Datasheet, PDF (10/10 Pages) Vishay Siliconix – DG419

DG417/418/419
Vishay Siliconix
"APPLICATIONS (CONT'D)
Micropower UPS Transfer Switch
Programmable Gain Amplifier
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.
When the 5-V supply comes back up, the resistor divider
senses the presence of at least 3.5 V, and causes a new
change of state in the analog switch, restoring normal
operation.
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
FET driver. It translates a TTL control signal into –8-V, 0-V level
outputs to drive the gate.
V_CC
(5 V)
D₁
R₁
V_SENSE
453 kW
Memory
R₂
383 kW
V+ _SW1 VL
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
FIGURE 12. Programmable Gain Amplifier
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4-10
+5 V
V_L
S₁
S₂
V+
GaAs FET
D ^VOUT
GND
DG419
V–
–8 V
FIGURE 13. GaAs FET Driver
Document Number: 70051
S-52433—Rev. E, 06-Sep-99