Datasheet

Electrical characteristics STM32F401xD STM32F401xE
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6.3.8 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 54. However, the recommended clock input
waveform is shown in Figure 22.
The characteristics given in Table 35 result from tests performed using an high-speed
external clock source, and under ambient temperature and supply voltage conditions
summarized in Table 14.
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 54. However, the recommended clock input
waveform is shown in Figure 23.
The characteristics given in Table 36 result from tests performed using an low-speed
external clock source, and under ambient temperature and supply voltage conditions
summarized in Table 14.
Table 35. High-speed external user clock characteristics
Symbol Parameter Conditions Min Typ Max Unit
f
HSE_ext
External user clock source
frequency
(1)
1-50MHz
V
HSEH
OSC_IN input pin high level voltage 0.7V
DD
-V
DD
V
V
HSEL
OSC_IN input pin low level voltage V
SS
-0.3V
DD
t
w(HSE)
t
w(HSE)
OSC_IN high or low time
(1)
1. Guaranteed by design, not tested in production.
5--
ns
t
r(HSE)
t
f(HSE)
OSC_IN rise or fall time
(1)
--10
C
in(HSE)
OSC_IN input capacitance
(1)
-5-pF
DuCy
(HSE)
Duty cycle 45 - 55 %
I
L
OSC_IN Input leakage current V
SS
≤ V
IN
≤ V
DD
--±1µA
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