Datasheet

Functional overview STM32L010F4/K4
18/91 DS12323 Rev 2
3.4 Reset and supply management
3.4.1 Power supply schemes
• V
DD
(1.8 to 3.6 V): external power supply for I/Os and the internal regulator. Provided
externally through V
DD
pins.
• V
SSA
, V
DDA
(1.8 to 3.6 V): external analog power supplies for ADC, reset blocks, RCs
and PLL. V
DDA
and V
SSA
must be connected to V
DD
and V
SS
, respectively.
3.4.2 Power supply supervisor
The STM32L010F4/K4 feature an integrated zeropower power-on reset (POR)/power-down
reset (PDR) that can be coupled with a brownout reset (BOR) circuitry.
After the V
DD
threshold is reached, the option byte loading process starts, either to confirm
or modify default thresholds, or to disable the BOR permanently.
The BOR is active at power-on, and ensures proper operation starting from 1.8 V, whatever
the power ramp-up phase before it reaches 1.8 V.
Five BOR thresholds are available through option bytes, starting from 1.8 V to 3 V. To
reduce the power consumption in Stop mode, it is possible to automatically switch off the
internal reference voltage (V
REFINT
) in Stop mode. The device remains in reset mode when
V
DD
is below a specified threshold, V
POR/PDR
or V
BOR
, without the need for any external
reset circuit.
3.4.3 Voltage regulator
The regulator has three operation modes: main (MR), low power (LPR) and power down.
• MR is used in Run mode (nominal regulation)
• LPR is used in the Low-power run, Low-power sleep and Stop modes
• Power down is used in Standby mode. The regulator output is high impedance, the
kernel circuitry is powered down, inducing zero consumption but the contents of the
registers and RAM are lost except for the standby circuitry (wakeup logic, IWDG, RTC,
LSI, LSE crystal 32 kHz oscillator, RCC_CSR).
3.4.4 Boot modes
At startup, BOOT0 pin and nBOOT0, nBOOT1 and nBOOT_SEL option bits are used to
select one of the three following boot options:
• Boot from Flash memory
• Boot from system memory
• Boot from embedded RAM
The bootloader is located in system memory. It is used to reprogram the Flash memory by
using SPI1 (PA4, PA5, PA6 and PA7) or USART2 (PA2, PA3).
If the bootloader is activated (the bootloader is active on all empty devices due to the empty
check mechanism), then the above mentioned bits are configured depending on whether
SPI1 or USART2 functionality is used.
See the application note STM32 microcontroller system memory boot mode (AN2606) for
more details.
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