RV-8523 Datasheet, PDF (23/57 Pages) MICORO CRYSTAL SWITZERLAND – Real Time Clock

Micro Crystal
Real Time Clock / Calendar Module
RV-8523
9.2. POWER MANAGEMENT
The RV-8523 has two power supply pins:
• V_DD - the main power supply input pin
• V_BAT - the battery backup input pin
The RV-8523 has two power management functions implemented:
• Battery switchover function
• Battery low detection function
The power management functions are controlled by the control bits PM[2:0] in register Control 3 (02h):
PM[2:0]
000
001
010, 011¹⁾
100
101
110
111^{2) 3)}
Function
Battery switchover function is enabled in standard mode
Battery low detection function is enabled
Battery switchover function is enabled in direct switching mode
Battery low detection function is enabled
Battery switchover function is disabled - only one power supply (VDD)
Battery low detection function is enabled
Battery switchover function is enabled in standard mode
Battery low detection function is disabled
Battery switchover function is enabled in direct switching mode
Battery low detection function is disabled
Not allowed
Battery switchover function is disabled - only one power supply (VDD)
Battery low detection function is disabled
1) _{When the battery switchover function is disabled, the RV-8523 works only with the power supply VDD.}
2) _{When the battery switchover function is disabled, the RV-8523 works only with the power supply VDD; VBAT must be put to ground and the}
battery low detection function is disabled.
3) _{Default value.}
9.2.1.STANDBY MODE
When the device is first powered up from the battery (V_BAT) but without a main supply (V_DD), the RV-8523
automatically enters the standby mode. In standby mode the RV-8523 does not draw any power from the backup
battery until the device is powered up from the main power supply V_DD. Thereafter, the device switches over to
battery backup mode whenever the main power supply V_DD is lost.
It is also possible to enter into standby mode when the chip is already supplied by the main power supply V_DD and a
backup battery is connected. To enter the standby mode, the power management control bits PM[2:0] have to be
set logic 111. Then the main power supply V_DD must be removed. As a result of it, the RV-8523 enters the standby
mode and does not draw any current from the backup battery before it is powered up again from main supply V_DD.
23/57