STM8S207S8T3C View Datasheet(PDF) - STMicroelectronics

Part Name

Description

Manufacturer

STM8S207S8T3C

Performance line, 24 MHz STM8S 8-bit MCU, up to 128 KB Flash, integrated EEPROM, 10-bit ADC, timers, 2 UARTs, SPI, I²C, CAN

STMicroelectronics 

STM8S207xx, STM8S208xx

Electrical characteristics

Table 32. HSE oscillator characteristics

Symbol

Parameter

Conditions

Min

Typ

Max

Unit

fHSE

External high speed oscillator

frequency

1

24

MHz

RF Feedback resistor

C(1) Recommended load capacitance (2)

220

kΩ

20

pF

IDD(HSE) HSE oscillator power consumption

C = 20 pF,

fOSC = 24 MHz

C = 10 pF,

fOSC = 24 MHz

gm Oscillator transconductance

tSU(HSE)(4) Startup time

5

VDD is stabilized

6 (startup)

2 (stabilized)(3)

mA

6 (startup)

1.5 (stabilized)(3)

mA/V

1

ms

1. C is approximately equivalent to 2 x crystal Cload.

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

Refer to crystal manufacturer for more details

3. Data based on characterization results, not tested in production.

4. tSU(HSE) is the start-up time measured from the moment it is enabled (by software) to a stabilized 24 MHz oscillation is

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

Figure 17. HSE oscillator circuit diagram

Rm

Lm

CO

Cm

Resonator

CL1

OSCIN

Resonator

OSCOUT

CL2

fHSE to core

RF

gm

Consumption

control

STM8

HSE oscillator critical gm formula

gmcrit = (2 × Π × fHSE)2 × Rm(2Co + C)2

Rm: Notional resistance (see crystal specification)

Lm: Notional inductance (see crystal specification)

Cm: Notional capacitance (see crystal specification)

Co: Shunt capacitance (see crystal specification)

CL1=CL2=C: Grounded external capacitance

gm >> gmcrit

Doc ID 14733 Rev 12

65/103

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