EVB-VF522R3 Platform User’s Guide, Rev. 0, 11/2014
Freescale Semiconductor, Inc.
7
Power management scheme
battery, for example 2032 or 2025, and the J8 header (see
Table 15
) selects if the MCU VBAT pin is
powered from it or the main MCU 3.3V rail (see
Figure 5. Backup battery
4.6
MCU supply routing
4.6.1
MCU core power
An external ballast transistor (Q2) is used to generate 1.2V for the MCU core (see
); depending
on the R28 configuration (see
Table 15
), its collector can be powered from one of the below rails:
•
1.5V (default),
•
3.3V (to test low-power applications without 1.5V rail, e.g. without DDR); in this case, the optional
diodes D2 and D3 shall be populated.
Refer to the AN4807 Application Note for details.
Figure 6. MCU core power
