23.6.2.1. Initialization
The voltage reference output is disabled after any Reset.
23.6.2.2. Enabling, Disabling, and Resetting
The voltage reference output is enabled/disabled by setting/clearing the Voltage Reference Output
Enable bit in the Voltage Reference register (VREF.VREFOE).
23.6.2.3. Selecting a Voltage Reference
The Voltage Reference Selection bit field in the VREF register (VREF.SEL) selects the voltage of INTREF
to be applied to analog modules, e.g. the ADC.
23.6.2.4. Sleep Mode Operation
The Voltage Reference output behavior during sleep mode can be configured using the Run in Standby
bit and the On Demand bit in the Voltage Reference register (VREF.RUNSTDBY, VREF.ONDEMAND),
see the following table:
Table 23-2. VREF Sleep Mode Operation
VREF.ONDEMAND VREF.RUNSTDBY Voltage Reference Sleep behavior
-
-
Disable
0
0
Always run in all sleep modes
except
standby sleep mode
0
1
Always run in all sleep modes
including
standby sleep mode
1
0
Only run if requested by the ADC, in all sleep modes
except
standby sleep mode
1
1
Only run if requested by the ADC, in all sleep modes
including
standby sleep mode
23.6.3. Battery Backup Power Switch
23.6.3.1. Initialization
The Battery Backup Power Switch (BBPS) is disabled at power-up, and the backup domain is supplied by
main power.
23.6.3.2. Forced Battery Backup Power Switch
The Backup domain is always supplied by the VBAT supply pin when the Configuration bit field in the
Battery Backup Power Switch Control register (BBPS.CONF) is written to 0x2 (FORCED).
23.6.3.3. Automatic Battery Backup Power Switch
The supply of the backup domain can be switched automatically to VBAT supply pin by the Automatic
Power Switch or by using the BOD33.
The supply of the backup domain can be switched automatically to VDD supply pin either by the
Automatic Power Switch or the Main Power Pin when VDD and VDDCORE are restored.
Automatic Power Switch (APWS)
When the Configuration bit field in the Battery Backup Power Switch register (BBPS.CONF) is selecting
the APWS, the Automatic Power Switch will function as Battery Backup Power Switch.
The Automatic Power switch allows to switch the supply of the backup domain from VDD to VBAT power
and vice-versa.
When the Automatic Power Switch configuration is selected, the Automatic Power Switch Ready bit in the
Status register (STATUS.APWSRDY) is set when the Automatic Power Switch is ready to operate. The
Atmel SAM L22G / L22J / L22N [DATASHEET]
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