Sub-Ghz Radio Clocks; Internal Oscillators; Hse32 Reference Clock; Table 29. Lora Mode Intermediate Frequencies - STMicroelectronics STM32WL5 Series Reference Manual

Sub-GHz radio (SUBGHZ)
5.4

Sub-GHz radio clocks

5.4.1

Internal oscillators

The following sub-GHz radio dedicated internal RC oscillators are available:
• 64 kHz RC oscillator
–
–
•
13 MHz RC oscillator, enabled for all sub-GHz radio SPI communication
The frequency of each sub-GHz radio internal oscillators is calibrated using the HSE32
clock at every sub-GHz radio transition from Deep-Sleep or Sleep-to-Standby, and after a
sub-GHz radio reset. The calibration can also be done on demand by the command
Calibrate().
5.4.2

HSE32 reference clock

The high-precision 32 MHz frequency needed for the sub-GHz radio transmission and
reception is taken from HSE32. The HSE32 clock can also be used by the MCU. The use of
an external crystal (XTAL) or a temperature compensated crystal oscillator (TCXO) are
supported. The used clock source is configured in the RCC (see
with trimming
When using the HSE32 with a XTAL, the load capacitors are provided by the integrated
capacitor banks that can be trimmed. The trimming is provided by SUBGHZ_HSEINTRIMR
and SUBGHZ_HSEOUTRIMR registers. The load capacitances on OSC_IN and OSC_OUT
can be trimmed separately. Software trimming must be applied after the sub-GHz radio
entered Standby with HSE32 mode.
The TCXO regulator, integrated in the sub-GHz radio, can be used to supply an external
temperature compensated crystal oscillator (TCXO). The regulated V
controlled through set_TcxoMode()command.
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Table 29. LoRa mode intermediate frequencies

Setting name
LORA_BW_500
LORA_BW_250
LORA_BW_125
LORA_BW_62
LORA_BW_41
LORA_BW_31
LORA_BW_20
LORA_BW_15
LORA_BW_10
LORA_BW_7
optionally used during the sub-GHz radio Sleep mode to wake up the transceiver
when performing periodic or duty cycled operations
used by the sub-GHz radio RTC for time based events
for more details).
Bandwidth [kHz]
500
250
125
62.5
41.67
31.25
20.83
15.63
10.42
7.81
RM0453 Rev 5
RM0453
f [kHz]
if
0
250
167
250
167
250
167
250
Section 7.2.1: HSE32 clock
supply level is
DDTCXO