STM32L452XX Datasheet, PDF(126/210 Page) STMicroelectronics – Ultra-low-power with FlexPowerControl

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STM32L452XX Datasheet, PDF (126/210 Pages) STMicroelectronics – Ultra-low-power with FlexPowerControl

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Electrical characteristics

STM32L452xx

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

The high-speed external (HSE) clock can be supplied with a 4 to 48 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 56. 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).

Symbol

Table 56. HSE oscillator characteristics(1)

Parameter

Conditions(2)

Min Typ Max Unit

fOSC_IN Oscillator frequency

Feedback resistor

During startup(3)

48 MHz

200

kâ¦

5.5

VDD = 3 V,

Rm = 30 â¦,

CL = 10 pF@8 MHz

- 0.44 -

VDD = 3 V,

Rm = 45 â¦,

CL = 10 pF@8 MHz

- 0.45 -

IDD(HSE) HSE current consumption

VDD = 3 V,

Rm = 30 â¦,

- 0.68 -

CL = 5 pF@48 MHz

VDD = 3 V,

Rm = 30 â¦,

- 0.94 -

CL = 10 pF@48 MHz

VDD = 3 V,

Rm = 30 â¦,

- 1.77 -

CL = 20 pF@48 MHz

Maximum critical crystal

transconductance

tSU(HSE)(4) Startup time

Startup

VDD is stabilized

1.5 mA/V

1. Guaranteed by design.

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

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

otSsUc(iHllaSEtio) nis

the startup

is reached.

time

This

measured from the moment it is enabled (by software) to

value is measured for a standard crystal resonator and it

a stabilized 8 MHz

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 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.

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