STM32F051K4U6 Datasheet, PDF(58/104 Page) STMicroelectronics – Low- and medium-density advanced ARM™-based 32-bit MCU with 16 to 64 Kbytes Flash, timers, ADC, DAC and comm. interfaces

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STM32F051K4U6 Datasheet, PDF (58/104 Pages) STMicroelectronics – Low- and medium-density advanced ARM™-based 32-bit MCU with 16 to 64 Kbytes Flash, timers, ADC, DAC and comm. interfaces

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STM32F051x

Electrical characteristics

Note:

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

The high-speed external (HSE) clock can be supplied with a 4 to 32 MHz 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 36. 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 36. HSE oscillator characteristics

Symbol

Parameter

Conditions(1)

Min(2) Typ Max(2) Unit

fOSC_IN Oscillator frequency

RF Feedback resistor

During startup(3)

32 MHz

- 200 -

kÎ©

8.5

VDD=3.3 V, Rm= 30Î©,

CL=10 pF@8 MHz

0.4

IDD HSE current consumption

VDD=3.3 V, Rm= 45Î©,

CL=10 pF@8 MHz

0.5

VDD=3.3 V, Rm= 30Î©,

CL=5 pF@32 MHz

0.8

VDD=3.3 V, Rm= 30Î©,

CL=10 pF@32 MHz

VDD=3.3 V, Rm= 30Î©,

CL=20 pF@32 MHz

1.5

gm Oscillator transconductance

tSU(HSE)(4) Startup time

Startup

VDD is stabilized

- mA/V

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

2. Guaranteed by design, not tested in production.

3. This consumption level occurs during the first 2/3 of the tSU(HSE) startup time

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

the requirements of the crystal or resonator (see Figure 14). 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.

For information on electing the crystal, refer to the application note AN2867 âOscillator

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

Doc ID 022265 Rev 3

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