Mouser Electronics White Paper
Figure 6 shows the current draw from a 3.3V supply in each low-
power mode with various levels of static random-access memory
(SRAM) data retention. The text on the right side of the figure
shows the wake-up signals available in each mode. These might
include a reset pattern on the I3C line in Shutdown mode, an
independent watchdog (IWDG) input in Standby mode, and a
programmable voltage detector (PVD) interrupt or a comparator
(COMP) transition in response to an analog signal in Stop 2 mode.
The device also features a brown-out reset (BOR) function that keeps
the device under reset until the supply voltage exceeds a specified
threshold. BOR is active in all modes except Shutdown mode. To
optimize performance and efficiency, designers can select the
modes that provide the optimal trade-off between power efficiency,
SRAM data retention, start-up time, and available wake-up sources.
The STM32U3 features 256kB of SRAM, consisting of several
separate blocks that can be individually powered down in Stop
modes to reduce power consumption further, and accommodates
up to 1MB of flash memory. To further reduce BOM count, it
also includes a variety of integrated peripherals, including
16 timers, a touch-sensing controller, two analog-to-digital
converters (ADCs), two digital-to-analog converters (DACs),
two op amps, a comparator, and a temperature sensor. It also
supports USB, SPI, I
2
C, I3C, and CAN FD connectivity.
The STM32U3 is RoHS compliant, featuring lead- and antimony-
free construction. Its decade-long longevity and availability
support long-term deployments in industrial and remote systems,
minimizing waste from early obsolescence. All the STM32U3 features
combine to support ST's broader sustainability strategy and goal of
reaching carbon neutrality by 2027,
15
and furthermore, ST provides
PCF data on request via the company's online support portal.
Figure 6: Mode (left), current draw (middle), and wake-up sources (right) for Shutdown, Standby, Stop, Sleep, and Run modes
for the STM32U3 operating on a 3.3V supply. (Source: STMicroelectronics; redrawn by Mouser Electronics)
