STM32F205RFT6 Datasheet, PDF (25/178 Pages) List of Unclassifed Manufacturers – ARM-based 32-bit MCU, 150DMIPs, up to 1 MB Flash/128+4KB RAM, USB OTG HS/FS, Ethernet, 17 TIMs, 3 ADCs, 15 comm. interfaces & camera

STM32F20xxx
Functional overview
Figure 6. Regulator OFF/internal reset ON
Power-down reset risen
before VCAP_1/VCAP_2 stabilization
External VCAP_1/2
power supply supervisor
Ext. reset controller active
Application reset
signal (optional)
when VCAP_1/2 < 1.08 V
VDD
(1.8 to 3.6 V)
1.2 V
PA0
VDD
NRST
REGOFF
VCAP_1 IRROFF
VCAP_2
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The following conditions must be respected:
• V_DD should always be higher than V_{CAP_1} and V_{CAP_2} to avoid current injection
between power domains.
• If the time for V_{CAP_1} and V_{CAP_2} to reach 1.08 V is faster than the time for V_DD to
reach 1.8 V, then PA0 should be kept low to cover both conditions: until V_{CAP_1} and
V_{CAP_2} reach 1.08 V and until V_DD reaches 1.8 V (see Figure 8).
• Otherwise, If the time for V_{CAP_1} and V_{CAP_2} to reach 1.08 V is slower than the time for
V_DD to reach 1.8 V, then PA0 should be asserted low externally (see Figure 9).
• If V_{CAP_1} and V_{CAP_2} go below 1.08 V and V_DD is higher than 1.8 V, then a reset must
be asserted on PA0 pin.
Regulator OFF/internal reset OFF
On WLCSP64+2 package, this mode activated by connecting REGOFF to V_SS and IRROFF
to V_DD. IRROFF cannot be activated in conjunction with REGOFF. This mode is available
only on the WLCSP64+2 package. It allows to supply externally a 1.2 V voltage source
through V_{CAP_1} and V_{CAP_2} pins. In this mode, the integrated power-on reset (POR)/ power-
down reset (PDR) circuitry is disabled.
An external power supply supervisor should monitor both the external 1.2 V and the external
V_DD supply voltage, and should maintain the device in reset mode as long as they remain
below a specified threshold. The V_DD specified threshold, below which the device must be
maintained under reset, is 1.8 V. This supply voltage can drop to 1.7 V when the device
operates in the 0 to 70 °C temperature range. A comprehensive set of power-saving modes
allows to design low-power applications.
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