STMicroelectronics STM32WL5 Series User Manual

RM0453 Rev 5 293/1450
RM0453 Reset and clock control (RCC)
371
Frequency trimming
When using HSE32 with external crystal, the load capacitors are provided by the integrated
capacitor banks, that can be trimmed. The HSE32 load capacitor trimming allows a
compensation of device manufacturing process variations, used crystal and PCB design.
The HSE32 frequency can be tuned in the application via the sub-GHz radio registers
SUBGHZ_HSEINTRIMR and SUBGHZ_HSEOUTRIMR. For more information see
Section 5.4: Sub-GHz radio clocks.
The HSE32 frequency can be measured by outputting the HSE32 clock on the MCO when
in Run mode.
External source (HSE32 TXCO)
In this mode, an external TXCO clock source must be provided. This external source
frequency must be 32 MHz. This mode is selected by setting the HSEBYPPWR and
HSEON
bits in the RCC clock control register (RCC_CR). The external clock signal (refer to
the datasheet) must drive the following pins (see Figure 28: HSE32 clock sources):
• OSC_IN and OSC_OUT pins: OSC_IN pin must be driven, while the OSC_OUT pin
must be left not connected.
The TCXO supply can be provided by the device on PB0/VDDTCXO. The V
DDTCXO
supply
is also enabled with the HSEBYPPWR bit in RCC clock control register (RCC_CR) before
enabling the HSE32 oscillator. V
DDTCXO
supply level and TCXO clock startup timeout can
be configured through the sub-GHz radio Set_TcxoMode() command (see Section 5:
Sub-GHz radio (SUBGHZ) for more details).
Figure 29. HSE32 TCXO control
The control of the HSE32 external TCXO can be done in the following ways:
• powered by V
DDTCXO
:
– Set the voltage level inside the sub-GHz radio by using the Set_TcxoMode()
command, before enabling the VDDTCXO regulator.
– Set the HSEBYPPWR bit to 1 to use the VDDTCXO regulator.
– Enable the HSE32 use with external TCXO in Run mode for the CPUs with the
HSEON bit.The availability of the clock can be checked with the HSERDY bit.
– Enable the HSE32 use with TXCXO for the sub-GHz radio with the sub-GHz radio
Set_TcxoMode() command when in sub-GHz radio Standby mode. It is
recommended to issue a sub-GHz radio calibration command once the HSE32
clock is available.
MSv62607V2
OSC
HSE32
TCXO
LDO
TCXO
VDD TCXO
PB0-VDDTCXO
VDDRF
OSC_IN
OSC_OUT NC
HSEON
OSC
Control
HSEBYPPWR
CLK
PB0 GPIO
oscon
tcxoon
0
1
Radio control
RDY
Control
en
clkHSEclk
HSERDY
R
C
LIN
Note: Force SUBGHZ_HSEINTRIMR = 0x00
to get C
LIN
= 11.3 pF.

STMicroelectronics STM32WL5 Series Specifications

General

Brand	STMicroelectronics
Model	STM32WL5 Series
Category	Microcontrollers
Language	English