UPD4991ACX Renesas Electronics America, UPD4991ACX Datasheet - Page 55

• Manufacturer Part Number: UPD4991ACX
• Manufacturer: Renesas Electronics America

Specifications of UPD4991ACX

• Lead Free Status / RoHS Status: Supplier Unconfirmed

4.4 Back-up Circuit
8 shows an example of using a Ni-Cd battery for back-up, and Figure 4-9 shows an example of using a super capacitor
(high-capacitance, electric double-layer capacitor).
Because the PD4991A is a CMOS IC, it can provide a back-up operation with a low-voltage battery. Figure 4-
If a 1.0-F super capacitor (such as FY0Z105) is used, the PD4991A can be backed up for several days.
GND
+5 V
GND
+5 V
2SA1175
15 k
4.7 k
Super capacitor
(FY series)
D
Figure 4-9. Example of Back-up Circuit Using Super Capacitor
1 k
Figure 4-8. Example of Back-up Circuit Using Ni-Cd Battery
CHAPTER 4 ELECTRICAL SPECIFICATIONS AND INTERFACE
2SC2785
R
1SS53
510
1SS53
Ni-Cd
3.6 V
C
+
+
C
V
V
DD
SS
V
V
PD4991A
DD
SS
PD4991A
TP
TP
TP
TP
1
2
1
2
C: Supply voltage stabilization capacitor
R: For inrush current prevention
D: Shottky barrier diode
(1 to 10 F)
Tantalum electrolytic, etc.
(depends on current capacity of +5 V)
(V
C: Supply voltage stabilization capacitor
F
(1 to 10 F)
Tantalum electrolytic, etc.
10 k
0.3 V)
10 k
+5 V
+5 V
53