ST STM32G4 Nucleo-64, User Manual

Page: 22 / 43

If this order is not respected, the board may be powered by USB first, then by VIN or E5V as the following risks
may be encountered:
1.
If more than 300 mA current is needed by the board, the PC may be damaged or the current supplied can be
limited by the PC. As a consequence, the board is not powered correctly.
2. 300 mA is requested at enumeration so there is risk that the request is rejected and the enumeration does
not succeed if the PC cannot provide such current. Consequently, the board is not power supplied (LED LD3
remains OFF).
6.5 Clock sources
6.5.1 HSE clock (high-speed external clock)
There are four ways to configure the pins corresponding to the high-speed external clock (HSE):
•
MCO from ST-LINK : MCO output of ST-LINK is used as input clock. This frequency cannot be changed, it is
fixed at 8 MHz and connected to the PF0-OSC_IN of the STM32 microcontroller. The configuration must be:
–
SB27 ON
– SB25 and SB26 OFF
– SB24 and SB28 OFF
• HSE on-board oscillator from X3 crystal (default) : For typical frequencies and its capacitors and
resistors, refer to the STM32 microcontroller datasheet and to the Oscillator design guide for STM8S,
STM8A and STM32 microcontrollers Application note (AN2867) for the oscillator design guide. The X3
crystal has the following characteristics: 24 MHz, 6 pF load capacitance, 20 ppm. It is recommended to use
NX2016SA-24MHz-EXS00A-CS10820 manufactured by NDK. The configuration must be:
–
SB25 and SB26 ON
– SB24 and SB28 OFF
– SB27 OFF
– C56 and C59 soldered with 6.8 pF capacitors
• Oscillator from external PF0 : from an external oscillator through the pin 29 of the CN7 connector. The
configuration must be:
–
SB28 ON
– SB24 OFF
– SB25 and SB26 OFF
– SB27 OFF
• HSE not used : PF0 and PF1 are used as GPIOs instead of as clock. The configuration must be:
– SB24 and SB28 ON
– SB27 OFF
– SB25 and SB26 OFF
6.5.2 LSE clock (low-speed external clock) – 32.768 kHz
There are three ways to configure the pins corresponding to the low-speed clock (LSE):
•
On-board oscillator (default) : X2 crystal. Refer to the Oscillator design guide for STM8S, STM8A and
STM32 microcontrollers application note (AN2867). It is recommended to use NX3215SA-32.768kHz-
EXS00A-MU00525 (32.768 kHz, 6 pF load capacitance, 20 ppm) from NDK.
–
SB30 and SB31 ON
– SB29 and SB32 OFF
• Oscillator from external PC14 : from external oscillator through the pin 25 of CN7 connector. The
configuration must be:
–
SB29 and SB32 ON
– SB30 and SB31 OFF
• LSE not used : PC14 and PC15 are used as GPIOs instead of low-speed clock. The configuration must be:
– SB29 and SB32 ON
– SB30 and SB31 OFF
UM2505
Clock sources
UM2505 - Rev 2
page 22/43