STM32F427NET7TR datasheet(118/231 Pages) STMICROELECTRONICS

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Electrical characteristics

STM32F427xx STM32F429xx

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Figure 28. Low-speed external clock source AC timing diagram

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

The high-speed external (HSE) clock can be supplied with a 4 to 26 MHz crystal/ceramic

resonator oscillator. All the information given in this paragraph are based on

characterization results obtained with typical external components specified in Table 39. 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).

Table 39. 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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