When VDD crosses below the brown-out threshold level, the BOD33 can generate either an interrupt, a
Reset, or an Automatic Battery Backup Power Switch, depending on the BOD33 Action bit field
(BOD33.ACTION).
If VBAT is monitored, the BOD33 compares the voltage with the brown-out threshold level set in the
BOD33 Backup Level field in the BOD33 register (BOD33.BKUPLEVEL).
When VBAT crosses below the backup brown-out threshold level, the BOD33 can generate either an
interrupt or a Reset.
The BOD33 detection status can be read from the BOD33 Detection bit in the Status register
(STATUS.BOD33DET).
At start-up or at Power-On Reset (POR), the BOD33 register values are loaded from the NVM User Row.
Related Links
on page 40
23.6.5.4. 1.2V Brown-Out Detector (BOD12)
The BOD12 is calibrated in production and its calibration configuration is stored in the NVM User Row.
This configuration must not be changed to assure the correct behavior of the BOD12. The BOD12
generates a reset when 1.2V crosses below the preset brown-out level. The BODCORE is always
disabled in standby sleep mode.
Related Links
23.6.5.5. Continuous Mode
Continuous mode is the default mode for BOD33.
The BOD33 is continuously monitoring the supply voltage (VDD or VBAT, depending on BOD33.VMON) if
it is enabled (BOD33.ENABLE=1) and if the BOD33 Configuration bit in the BOD33 register is cleared
(BOD33.ACTCFG=0 for active mode, BOD33.STDBYCFG=0 for standby mode).
23.6.5.6. Sampling Mode
The Sampling Mode is a low-power mode where the BOD33 is being repeatedly enabled on a sampling
clock’s ticks. The BOD33 will monitor the supply voltage for a short period of time and then go to a low-
power disabled state until the next sampling clock tick.
Sampling mode is enabled in Active mode for BOD33 by writing the ACTCFG bit (BOD33.ACTCFG=1).
Sampling mode is enabled in Standby mode by writing to the STDBYCFG bit (BOD33.STBYCFG=1). The
frequency of the clock ticks (F
clksampling
) is controlled by the Prescaler Select bit groups in the BOD33
register (BOD33.PSEL).
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=
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2
PSEL + 1
The prescaler signal (F
clkprescaler
) is a 1KHz clock, output by the 32KHz Ultra Low Power Oscillator
OSCULP32K.
As the sampling clock is different from the APB clock domain, synchronization among the clocks is
necessary. See also
.
23.6.5.7. Hysteresis
A hysteresis on the trigger threshold of a BOD will reduce the sensitivity to ripples on the monitored
voltage: instead of switching RESET at each crossing of V
BOD
, the thresholds for switching RESET on
and off are separated (V
BOD-
and V
BOD+
, respectively).
Atmel SAM L22G / L22J / L22N [DATASHEET]
Atmel-42402E-SAM L22G / L22J / L22N_Datasheet_Complete-07/2016
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