STM32F429NET7TR datasheet(116/231 Pages) STMICROELECTRONICS

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Electrical characteristics

STM32F427xx STM32F429xx

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DocID024030 Rev 6

6.3.9

External clock source characteristics

High-speed external user clock generated from an external source

In bypass mode the HSE oscillator is switched off and the input pin is a standard I/O. The

external clock signal has to respect the Table 56: I/O static characteristics. However, the

recommended clock input waveform is shown in Figure 27.

The characteristics given in Table 37 result from tests performed using an high-speed

external clock source, and under ambient temperature and supply voltage conditions

summarized in Table 17.

Low-speed external user clock generated from an external source

In bypass mode the LSE oscillator is switched off and the input pin is a standard I/O. The

external clock signal has to respect the Table 56: I/O static characteristics. However, the

recommended clock input waveform is shown in Figure 28.

The characteristics given in Table 38 result from tests performed using an low-speed

external clock source, and under ambient temperature and supply voltage conditions

summarized in Table 17.

Table 37. High-speed external user clock characteristics

Symbol

Parameter

Conditions

Min

Typ

Max

Unit

fHSE_ext

External user clock source

frequency(1)

MHz

VHSEH

OSC_IN input pin high level voltage

0.7VDD

-VDD

VHSEL

OSC_IN input pin low level voltage

VSS

-0.3VDD

tw(HSE)

OSC_IN high or low time(1)

1. Guaranteed by design.

tr(HSE)

tf(HSE)

OSC_IN rise or fall time(1)

Cin(HSE) OSC_IN input capacitance(1)

-5

DuCy(HSE) Duty cycle

OSC_IN Input leakage current

VSS ≤ VIN ≤ VDD

±1

µA

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