STM32WL33C8 datasheet(61/91 Pages) STMICROELECTRONICS

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6.3.10

High-speed external clock

The high-speed external oscillator must be supplied with an external 48 MHz crystal specified for a 6 to 8 pF

loading capacitor. The STM32WL33xx includes internal programmable capacitances that can be used to tune the

crystal frequency to compensate the PCB parasitic one.

These internal load capacitors are made by a fixed one, in parallel with a 6-bit binary weighted capacitor bank.

Thanks to low CL step size (1-bit is typically 0.12 pF), very fine frequency tuning is possible. With typical XTAL

sensitivity of -14 ppm/pF, it is possible to trim a 48 MHz crystal, with a resolution of 1 ppm (5 ppm max).

The STM32WL33xx guarantees a very low frequency drift due to 0.2 V supply variations, supporting long

transmission times at low data rate.

Table 47. HSE frequency drift versus power supply drop

Symbol

Parameter

Conditions

Min.

Typ.

Max.

Unit

fDRIFT

Frequency drift versus

power-supply variation

200 mV VDD drop

±40

ppb

Table 48. HSE crystal requirements

Symbol

Parameter

Conditions(1)(2)

Min.

Typ.

Max.

Unit

fnom

Oscillator frequency

MHz

fTOL

Frequency accuracy

Initial accuracy at 25 °C

+/-10

ppm

Over temperature -40 °C to +85 °C

+/-20

Over temperature +85 °C to

+105 °C

+/-32

Aging over 10 years

+/-10

ESR

Equivalent series

resistance

Ω

CLOAD

Load capaticance

Cshunt

Shunt capacitance

-30%

0.71

Cmotion

Motional capacitance

-30%

2.03

Lmotion

Motional inductance

-30%

5.41

µH

Drive level

100

µW

1. A 48 MHz XTAL is specified for a specific reference: NX1612SA. A 48 MHz XTAL is specified for a specific reference:

NX1612SA.

2. For more information about the crystal selection, refer to the application note Oscillator design guide for STM8AF/AL/S,

STM32 MCUs and MPUs (AN2867).

STM32WL33xx

Electrical characteristics

DS14221 - Rev 5

page 61/91

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