Datasheet

SAM3X / SAM3A [DATASHEET]
Atmel-11057C-ATARM-SAM3X-SAM3A-Datasheet_23-Mar-15
270
16.4 Supply Controller Functional Description
16.4.1 Supply Controller Overview
The device can be divided into two power supply areas:
 The Backup VDDBU Power Supply: including the Supply Controller, a part of the Reset Controller, the Slow
Clock switch, the General Purpose Backup Registers, the Supply Monitor and the Clock which includes the
Real Time Timer and the Real Time Clock
 The Core Power Supply: including the other part of the Reset Controller, the Brownout Detector, the
Processor, the SRAM memory, the FLASH memory and the Peripherals
The Supply Controller (SUPC) controls the supply voltage of the core power supply. The SUPC intervenes when
the VDDUTMI power supply rises (when the system is starting) or when the Backup Low Power Mode is entered.
The SUPC also integrates the Slow Clock generator which is based on a 32 kHz crystal oscillator and an
embedded 32 kHz RC oscillator. The Slow Clock defaults to the RC oscillator, but the software can enable the
crystal oscillator and select it as the Slow Clock source.
The Supply Controller and the VDDUTMI power supply have a reset circuitry based on the NRSTB pin and a zero-
power power-on reset cell. The zero-power power-on reset allows the SUPC to start properly as soon as the
VDDUTMI voltage becomes valid. The NRSTB pin allows to reset the system from outside.
At startup of the system, once the backup voltage VDDUTMI is valid and the reset pin NRSTB is not driven low and
the embedded 32 kHz RC oscillator is stabilized, the SUPC starts up the core by sequentially enabling the internal
Voltage Regulator, waiting that the core voltage VDDCORE is valid, then releasing the reset signal of the core
“vddcore_nreset” signal.
Once the system has started, the user can program a supply monitor and/or a brownout detector. If the supply
monitor detects a voltage on VDDUTMI that is too low, the SUPC can assert the reset signal of the core
“vddcore_nreset” signal until VDDUTMI is valid. Likewise, if the brownout detector detects a core voltage
VDDCORE that is too low, the SUPC can assert the reset signal “vddcore_nreset” until VDDCORE is valid.
When the Backup Low Power Mode is entered, the SUPC sequentially asserts the reset signal of the core power
supply “vddcore_nreset” and disables the voltage regulator, in order to supply only the VDDUTMI power supply. In
this mode the current consumption is reduced to a few microamps for Backup part retention. Exit from this mode is
possible on multiple wake-up sources including an event on FWUP pin or WKUP pins, or a Clock alarm. To exit
this mode, the SUPC operates in the same way as system startup.