R01UH0823EJ0100 Rev.1.00 Page 255 of 1823
Jul 31, 2019
RX23W Group 12. Battery Backup Function
12.4 Usage Notes
1. When the VBATT pin is not used, connect the VBATT pin to the VCC pin.
2. When the battery backup function is not used, set the VBATTCR.VBATTDIS bit to 1 (battery backup function
disabled).
3. When the voltage level at the VBATT is lower than the guaranteed operation range, operation of the sub-clock and
RTC cannot be guaranteed. The RTC must be initialized to restart power supply after the VBATT pin falls below
the operation guaranteed voltage.
4. Writing to the RTC registers should be performed while power is being supplied from the VCC pin.
5. When VCC is higher than VDETBATT, the VCC pin and VBATT pin are not connected by means of circuitry.
When VCC is lower than VDETBATT and the switch is connected to the VBATT pin, if the voltage at the VBATT
pin becomes lower than VCC - 0.6 V, current may flow into the VBATT pin through the parasitic diode between the
VCC and VBATT pins.
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