SB configuration
MCU Power supply
SB132 ON
SB for VDD_USB input voltage
SB133 ON
SB for VDDIO2 PG [2-15] input voltage
SB146 ON
SB for VBAT input voltage
SB149 OFF / SB150 ON
SB for VDDA input voltage
For more detail about VDDA/VREFP power supply, refer to MCU datasheet
Warning:
The power sequence is not respected when using 1V8 VDD. Refer to the Getting started with
STM32L5 Series hardware development application note AN5211, and STM32L5xx products
datasheets for power sequencing.
6.9
OSC clock sources
Three clock sources are described below.
•
LSE is the 32.768 kHz crystal for the STM32 embedded RTC.
•
MCO is the 8 MHz clock from ST-LINK MCU for the STM32 microcontroller.
•
HSE is the 16 MHz oscillator for the STM32 microcontroller. This clock is not implemented in a basic
configuration.
6.9.1
LSE: OSC 32 KHz clock supply
There are three ways to configure the pins corresponding to the low-speed clock (LSE):
LSE on-board oscillator X2 crystal (Default configuration)
Refer to the AN2867 for oscillator design guide for STM32 microcontrollers, with the following characteristics:
32.768 kHz, 6 pF, 20 ppm. It is recommended to use NX2012SA- 32.768KHZ-EXS00A-MU00527 manufactured
by NDK. The following configuration is needed:
•
R34 and R35 ON
•
SB147 and SB148 OFF
Oscillator from external to PC14 input
From external oscillator through the pin 25 of the CN11 connector. The following configuration is needed:
•
R34 and R35 OFF
•
SB147 and SB148 ON
LSE not used
PC14 and PC15 are used as GPIOs instead of low-speed clocks. The following configuration is needed:
•
R34 and R35 OFF
•
SB147 and SB148 ON
6.9.2
OSC clock supply
There are four ways to configure the pins corresponding to the external high-speed clock (HSE):
HSE: on-board oscillator X3 crystal (Default: not connected)
For typical frequencies and its capacitors and resistors, refer to the STM32 microcontroller datasheet. Refer to the
AN2867 for oscillator design guide for STM32 microcontrollers. The X3 crystal has the following characteristics:
16 MHz, 8 pF, 20 ppm. It is recommended to use NX2016SA_16MHz_EXS00A-CS07826 manufactured by NDK.
The following configuration is needed:
UM2581
OSC clock sources
UM2581
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Rev 2
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