STM32F479AI datasheet(114/208 Pages) STMICROELECTRONICS

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Electrical characteristics

STM32F479xx

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DocID028010 Rev 2

Note:

For information on selecting the crystal, refer to the application note AN2867 “Oscillator

design guide for ST microcontrollers” available from www.st.com.

Figure 30. Typical application with a 32.768 kHz crystal

5.3.10

Internal clock source characteristics

The parameters given in Table 39 and Table 40 are derived from tests performed under

ambient temperature and VDD supply voltage conditions summarized in Table 17.

High-speed internal (HSI) RC oscillator

Table 38. LSE oscillator characteristics (fLSE = 32.768 kHz)(1)

1. Guaranteed by design.

Symbol

Parameter

Conditions

Min

Typ

Max

Unit

Feedback resistor

18.4

IDD

LSE current consumption

Low power mode(2)

2. LSE mode cannot be changed “on the fly” otherwise, a glitch can be generated on OSCIN pin.

µA

High drive mode(2)

ACCLSE(3)

3. This parameter depends on the crystal used in the application. Refer to application note AN2867.

LSE accuracy

− 500

500

ppm

Gm_crit_max Maximum critical crystal gm

Low power mode(2)

0.56

µA/V

High drive mode(2)

1.5

tSU(LSE)(4)

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

32.768 kHz oscillation is reached. This value is based on characterization and not tested in production. It is

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

Startup time

VDD is stabilized

Table 39. HSI oscillator characteristics (1)

Symbol

Parameter

Conditions

Min Typ Max Unit

fHSI

Frequency

MHz

ACCHSI

HSI user trimming step(2)

HSI oscillator accuracy

TA = –40 to 105 °C(3)

− 8-4.5

TA = –10 to 85 °C(3)

− 4-

TA = 25 °C(4)

− 1-

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