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15 Battery backup switchover function
15.1. Description of Battery backup switchover function
This function consists of a supply voltage detector "V
power source connected to "V
SW2B) located between the main power-source pin "V
Battery backup switchover block diagram)
The MOS-switches SW1, SW2A and SW2B are activated according to the result of the supply-voltage
detection of V
DET2
V
) or backup mode (RTC power supply = V
DD
The RTCs backup function is built in a way to prevent reverse current flow from V
mode, the I2C-bus and FOUT function are switched off and related terminals switched to Hi-Z.
V
BAT
Figure 26 Battery backup switchover block diagram
15.2 Reference characteristics of switching elements.
Table 33 Reference characteristics of switching elements.
Item
Limit of current.
Diode Vf
Diode IR
Use a secondary battery, EDLC, etc, with the charge current of 40 mA or less.
RX8130CE
ETM50E-07
" drops below a threshold (V
DD
and the RTC changes the operating modes between normal mode (RTC power supply =
BAT
SW2B
SW2A
RTC Power Supply
Value
40 mA Max.
0.60 V / 1 mA Typ.
0.85 V / 10 mA Typ.
5 nA Max.
Seiko Epson Corporation
15 Battery backup switchover function
" which detects if the supply voltage of the main
DET
2), and three MOS switches (SW1,SW2A and
DET
" and the backup power supply pin "V
DD
).
V
OUT
SW1
Condition
SW1 = SW2A = SW2B = ON, +25 C
= 3.0 V, +25 C
V
DD
VR = 5.5 V, -40 C
". (Figure 26
BAT
to V
. While in backup-
BAT
DD
V
DD
+85 C
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