Power supplies AN4661
10/54 DocID027559 Rev 5
1.1.4 Independent DSI supply for STM32F769xx/STM32F779xx devices
The DSI (Display Serial Interface) sub-system uses several power supply pins which are
independent from the other supply pins:
• The V
DDDSI
is an independent DSI power supply dedicated for DSI Regulator and MIPI
DPHY. This supply must be connected to global V
DD
.
• The V
CAPDSI
pin is the output of DSI Regulator (1.2V) which must be connected
externally to V
DD12DSI
.
• The V
DD12DSI
pin is used to supply the MIPI D-PHY, and to supply the clock and data
lanes pins. An external capacitor of 2.2 uF must be connected on V
DD12DSI
pin.
• The V
DDDSI
pin is an isolated supply ground used for DSI sub-system.
If the DSI functionality is not used at all, then:
• The V
DDDSI
pin must be connected to global V
DD
.
• The V
CAPDSI
pin must be connected externally to V
DD12DSI
but the external capacitor
is no more needed.
• The V
SSDSI
pin must be grounded.
1.1.5 Battery backup domain
Backup domain description
To retain the content of the RTC backup registers, backup SRAM, and supply the RTC when
V
DD
is turned off, V
BAT
pin can be connected to an optional standby voltage supplied by a
battery or by another source.
When the backup domain is supplied by V
BAT
(analog switch connected to V
BAT
because
V
DD
is not present), the following functions are available:
• PC14 and PC15 can be used as LSE pins only.
• PC13 can be used as tamper pin (TAMP1).
• PI8 can be used as tamper pin (TAMP2).
1.1.6 Voltage regulator
The voltage regulator is always enabled after reset. It works in three different modes
depending on the application modes.
• In Run mode, the regulator supplies full power to the 1.2 V domain (core, memories
and digital peripherals).
• In Stop mode, the regulator supplies low power to the 1.2 V domain, preserving the
contents of the registers and SRAM.
• In Standby mode, the regulator is powered down. The contents of the registers and
SRAM are lost except for those concerned with the standby circuitry and the backup
domain.
Note: Depending on the selected package, there are specific pins that should be connected either
to V
SS
or V
DD
to activate or deactivate the voltage regulator. Refer to the voltage regulator
section in the datasheet for more details.
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