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V
REF-
, V
REF+
V
REF+
is the input reference voltage for ADCs and DACs. It is also the output of the internal voltage
reference buffer (VREFBUF) when enabled. The VREF+ pin can be grounded when ADC and DAC are not
active.
The internal voltage reference buffer supports four output voltages, that are configured with the VRS[2:0]
field in VREFBUF_CSR register:
–
V
REF+
around 1.5 V. This requires V
DDA
≥ 1.8 V.
–
V
REF+
around 1.8 V. This requires V
DDA
≥ 2.1 V.
–
V
REF+
around 2.048 V. This requires V
DDA
≥ 2.4 V.
–
V
REF+
around 2.5 V. This requires V
DDA
≥ 2.8 V.
VREF- and VREF+ pins are not available on all packages. When not available, they are bonded to VSSA
and VDDA pins, respectively.
When the VREF+ pin is double-bonded to VDDA in a package, the internal VREFBUF is not available and
must be kept disabled.
V
REF-
must always be equal to V
SSA
.
The following figures present an overview of the STM32U575/585 devices power supply, depending on the SMPS
presence.
Figure 1.
STM32U575xx and STM32U585xx power supply overview (no SMPS)
USB transceiver
Core
SRAM1
SRAM2
SRAM3
SRAM4
Digital
peripherals
LSE crystal 32kHz oscillator
Backup registers
RCC_BDCR register
RTC
TAMP
BKPSRAM
V
DDA
domain
Backup domain
Standby circuitry
(Wakeup logic, IWDG)
Low-voltage detector
I/O ring
V
CORE
domain
Temperature sensor
Reset block
3 x PLL
Internal RC oscillators
Flash memory
VDDUSB
VDDIO2
V
DDIO1
I/O ring
PG[15:2]
V
DDIO2
VDDA
VSSA
VSS
VSS
V
DDIO2
domain
V
DD
domain
V
CORE
VSS
VDD
VBAT
VCAP
2 x A/D converters
2 x comparators
2 x D/A converters
2 x operational amplifiers
Voltage reference buffer
LDO regulator
AN5373
Power supplies
AN5373
-
Rev 1
page 4/37