MM32F103CET datasheet(53/89 Pages) MINDMOTION

53 / 89 page

DS_MM32F103xx_o_Ver1.13

Electrical characteristics

2. Guaranteed by design, not tested in production.

3. 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. 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.

4. The relatively low value of the RF resistance can be used to avoid problems arising

from the use of wet conditions to provide protection, this environment resulting in leak-

age and bias conditions have changed. However, if the MCU is applied in bad wet

conditions, the design needs to take this parameter into account.

5. tSU(HSE) is the startup time measured from the moment it is enabled (by software) to a

stabilized 8 MHz oscillation is reached. This value is measured for a standard crystal

resonator and it can vary significantly with the crystal manufacturer.

860676

Resonator with

intergrated capacitors

Resonator

Bias

controlled

gain

CL2

CL1

8MHz

OSC_IN

OSC_OUT

fHSE

Figure 16. Typical application with an 8 MHz crystal

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 characteriza-

tion results obtained with typical external components specified in the table below. In the

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

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

Refer to the crystal resonator manufacturer for more details on the resonator characteris-

tics (frequency, package, accuracy). Note: For CL1 and CL2, it is recommended to use a

high quality ceramic capacitor between 5pF and 15pF and select the crystal or resonator

that meets the requirements. Usually CL1 and CL2 have the same parameters. Crystal

manufacturers typically give the parameters of the load capacitance in a serial combina-

tion of CL1 and CL2. The load capacitance CL is calculated by: CL = CL1 x CL2/(CL1 + CL2)

+ Cstray, where Cstray is the capacitance of the pin and the capacitance associated with the

PCB or PCB. Its typical value is between 2pF and 7pF. WARNING: To avoid exceeding

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