STMicroelectronics Discovery kit for STM32L151/152 line - with STM32L152RC MCU STM32L152C-DISCO STM32L152C-DISCO Hoja De Datos

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STM32L15xCC STM32L15xRC STM32L15xUC STM32L15xVC
Functional overview
51
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.
Note:
The start-up time at power-on is typically 3.3 ms when BOR is active at power-up, the start-
up time at power-on can be decreased down to 1 ms typically for devices with BOR inactive 
at power-up.
The device features an embedded programmable voltage detector (PVD) that monitors the 
V
DD
/V
DDA
 power supply and compares it to the V
PVD
 threshold. This PVD offers 7 different 
levels between 1.85 V and 3.05 V, chosen by software, with a step around 200 mV. An 
interrupt can be generated when V
DD
/V
DDA
 drops below the V
PVD
 threshold and/or when 
V
DD
/V
DDA
 is higher than the V
PVD
 threshold. The interrupt service routine can then generate 
a warning message and/or put the MCU into a safe state. The PVD is enabled by software.
3.3.3 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 32K osc, RCC_CSR).
3.3.4 Boot 
modes
At startup, boot pins are used to select one of three boot options:
Boot from Flash memory
Boot from System memory
Boot from embedded RAM
The boot loader is located in System memory. It is used to reprogram the Flash memory by 
using USART1, USART2 or USB. See STM32™ microcontroller system memory boot mode 
AN2606 for details.