STM32F303C6 datasheet(67/115 Pages) STMICROELECTRONICS

67 / 115 page

DocID025083 Rev 5

67/115

STM32F303x6/x8

Electrical characteristics

100

For CL1 and CL2, it is recommended to use high-quality external ceramic capacitors in the

5 pF to 25 pF range (typ.), designed for high-frequency applications, and selected to match

the requirements of the crystal or resonator (see Figure 15). CL1 and CL2 are usually the

same size. The crystal manufacturer typically specifies a load capacitance which is the

series combination of CL1 and CL2. PCB and MCU pin capacitance must be included (10 pF

can be used as a rough estimate of the combined pin and board capacitance) when sizing

CL1 and CL2.

Note:

For information on selecting the crystal, refer to the application note AN2867 “Oscillator

design guide for ST microcontrollers” available from the ST website www.st.com.

Figure 15. Typical application with an 8 MHz crystal

1. REXT value depends on the crystal characteristics.

Low-speed external clock generated from a crystal/ceramic resonator

The low-speed external (LSE) clock can be supplied with a 32.768 kHz crystal/ceramic

resonator oscillator. All the information given in this paragraph are based on design

simulation results obtained with typical external components specified in Table 41. In the

application, the resonator and the load capacitors have to be placed as close as possible to

the oscillator pins to minimize output distortion and startup stabilization time. Refer to the

crystal resonator manufacturer for more details on the resonator characteristics (frequency,

package, accuracy).

STM32F303C6 Datasheet(PDF) 67 Page - STMicroelectronics