STM8L052R8 datasheet(76/109 Pages) STMICROELECTRONICS

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Electrical parameters

STM8L052R8

76/109

Doc ID023337 Rev 2

Figure 16.

HSE oscillator circuit diagram

HSE oscillator critical gm formula

Rm: Motional resistance (see crystal specification), Lm: Motional inductance (see crystal specification),

Cm: Motional capacitance (see crystal specification), Co: Shunt capacitance (see crystal specification),

CL1=CL2=C: Grounded external capacitance

gm >> gmcrit

LSE crystal/ceramic resonator oscillator

The LSE clock can be supplied with a 32.768 kHz crystal/ceramic resonator oscillator. All

the information given in this paragraph is based on characterization results with specified

typical external components. 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

(frequency, package, accuracy...).

OSC_OUT

OSC_IN

fHSE to core

CL1

CL2

STM8

Resonator

Consumption

control

Resonator

mcrit

HSE

()2 R

2Co

()

Table 29.

LSE oscillator characteristics

Symbol

Parameter

Conditions

Min.

Typ.

Max.

Unit

fLSE

Low speed external oscillator

frequency

32.768

kHz

Feedback resistor

ΔV = 200 mV

1.2

C(1)(2)

Recommended load capacitance

8pF

IDD(LSE)

LSE oscillator power consumption

VDD = 1.8 V

450

VDD = 3 V

600

VDD = 3.6 V

750

Oscillator transconductance

3(3)

µA/V

tSU(LSE)

(4)

Startup time

VDD is stabilized

C=CL1=CL2 is approximately equivalent to 2 x crystal CLOAD.

The oscillator selection can be optimized in terms of supply current using a high quality resonator with a small Rm value.

Refer to crystal manufacturer for more details.

Guaranteed by design. Not tested in production.

tSU(LSE) is the startup time measured from the moment it is enabled (by software) to a stabilized 32.768 kHz oscillation.

This value is measured for a standard crystal resonator and it can vary significantly with the crystal manufacturer.

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