3.4.6.1 Back-up

The purpose of Back-up mode is to achieve the lowest possible power consumption in a system that executes periodic wake-ups to perform tasks, but does not require fast start-up time.

PL360MB includes a back-up circuit with a battery (BT1) to maintain active RTC when the power supply of 3.3 volts shutdown and SAM4CMS enter in a low power mode. A voltage supervisor, U17, is also included.

Figure 3-18. Back-up Diagram
Note that there are three back-up resistor configurations:
  1. Back-up mode disabled (default option) when R105 resistor is placed.
  2. Back-up mode 1 (VBAT) enabled when R157 and R19 resistors are soldered (and R105 removed).
  3. Back-up mode 2 (voltage supervisor) enabled when resistors R157 and R20 are soldered (and R105 removed).

In addition, even the VDDIO and VDDIN pins of the SAM4CMS16C microcontroller could be supplied removing R66 resistor and soldering R65 resistor.

Figure 3-19. Back-up Circuit
Important: By default, back-up components and configuration resistors such as battery BT1 and resistors R157, R19, R20 and R65 are not populated.