STM32L010F4 datasheet(57/91 Pages) STMICROELECTRONICS

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DS12323 Rev 3

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STM32L010F4/K4

Electrical characteristics

time. Refer to the crystal resonator manufacturer for more details on the resonator

characteristics (frequency, package, accuracy).

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 (seeFigure 16). 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 Oscillator design guide for STM8AF/AL/S and

STM32 microcontrollers (AN2867) available from the ST website www.st.com.

Figure 16. HSE oscillator circuit diagram

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

characterization results obtained with typical external components specified in Table 35. 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

Table 34. HSE oscillator characteristics(1)

1. Guaranteed by design, not tested in production.

Symbol

Parameter

Conditions

Min

Typ

Max

Unit

fOSC_IN

Oscillator frequency

MHz

Feedback resistor

200

kΩ

Maximum critical crystal

transconductance

Startup

700

µA/V

tSU(HSE)(2)

2. Guaranteed by characterization results. 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.

Startup time

VDD is stabilized

OSC_OUT

OSC_IN

fHSE to core

CL1

CL2

STM32

Resonator

Consumption

control

Resonator

ai18235b

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