CD00253742 Datasheet, PDF(56/120 Page) STMicroelectronics – XL-density performance line ARM-based 32-bit MCU

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CD00253742 Datasheet, PDF (56/120 Pages) STMicroelectronics – XL-density performance line ARM-based 32-bit MCU

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Electrical characteristics

STM32F103xF, STM32F103xG

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

The high-speed external (HSE) clock can be supplied with a 4 to 16 MHz crystal/ceramic

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

results obtained with typical external components specified in Table 23. 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 characteristics (frequency,

package, accuracy).

Table 23.

Symbol

HSE 4-16 MHz oscillator characteristics(1)(2)

Parameter

Conditions

Min Typ Max Unit

fOSC_IN Oscillator frequency

RF Feedback resistor

Recommended load capacitance

versus equivalent serial

RS = 30 Î©

resistance of the crystal (RS)(3)

HSE driving current

VDD= 3.3 V, VIN = VSS

with 30 pF load

8 16 MHz

200 -

kÎ©

1 mA

gm Oscillator transconductance

tSU(HSE)(4) Startup time

Startup

VDD is stabilized

- mA/V

- ms

1. Resonator characteristics given by the crystal/ceramic resonator manufacturer.

2. Based on characterization results, not tested in production.

3. The relatively low value of the RF resistor offers a good protection against issues resulting from use in a

humid environment, due to the induced leakage and the bias condition change. However, it is

recommended to take this point into account if the MCU is used in tough humidity conditions.

4. 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

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 20). 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. Refer to the application note AN2867 âOscillator design guide for ST

microcontrollersâ available from the ST website www.st.com.

Figure 20. Typical application with an 8 MHz crystal

Resonator with

integrated capacitors

CL1

CL2

8 MH z

resonator

REXT(1)

OSC_IN

OSC_OU T

Bias

controlled

gain

1. REXT value depends on the crystal characteristics.

fHS E

STM32F103xx

ai14145

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Doc ID 16554 Rev 3

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