STM32F479AI datasheet(116/217 Pages) STMICROELECTRONICS

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Electrical characteristics

STM32F479xx

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DocID028010 Rev 3

time. Refer to the crystal resonator manufacturer for more details on the resonator

characteristics (frequency, package, accuracy).

For CL1 and CL2, it is recommended to use high-quality external ceramic capacitors in the

5 pF to 25 pF range (typ.), designed for high-frequency applications, and selected to match

the requirements of the crystal or resonator (see Figure 31). 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.

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 31. Typical application with an 8 MHz crystal

1. REXT value depends on the crystal characteristics.

Table 37. HSE 4-26 MHz oscillator characteristics (1)

1. Guaranteed by design.

Symbol

Parameter

Conditions

Min

Typ

Max

Unit

fOSC_IN

Oscillator frequency

MHz

Feedback resistor

200

IDD

HSE current consumption

VDD=3.3 V,

ESR= 30 Ω,

CL=5 pF@25 MHz

450

µA

VDD=3.3 V,

ESR= 30 Ω,

CL=10 pF@25 MHz

530

ACCHSE(2)

2. This parameter depends on the crystal used in the application. The minimum and maximum values must

be respected to comply with USB standard specifications.

HSE accuracy

− 500

500

ppm

Gm_crit_max Maximum critical crystal gm

Startup

mA/V

tSU(HSE)(3)

3. 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 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

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