15 Battery backup switchover function
RX8130CE
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ETM50E-07
Seiko Epson Corporation
44
Figure 33 V
DD
detection (VDET2) timing
V
DD
voltage drop detection (V
DET
2) is work always, in Normal mode.
Shorter SW1:OFF times are suitable to detect fast external voltage drops on V
DD
. On the other hand, in order to detect a
slower external voltage drop on V
DD
, a longer SW1:OFF detection time is needed. But longer SW1:OFF period increases
the current consumption.
Users are requested to evaluate SW1:OFF period based on actual system configuration and characteristics.
In backup mode V
DD
detection (V
DET
2) is activated once every 31.25 ms.
Note: Re-chargeable battery is charged through diode during1 the term of SW1 = OFF. Longer this term (ex. 256 ms)
makes decreasing battery charging efficiency.