Datasheet

DocID026289 Rev 6 83/149
STM32F411xC STM32F411xE Electrical characteristics
123
Figure 22. High-speed external clock source AC timing diagram
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 53. 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.
06Y9
9
+6(+
W
I+6(


7
+6(
W
W
U+6(
9
+6(/
W
Z+6(+
W
Z+6(/
Table 36. Low-speed external user clock characteristics
Symbol Parameter Conditions Min Typ Max Unit
f
LSE_ext
User External clock source
frequency
(1)
-
- 32.768 1000 kHz
V
LSEH
OSC32_IN input pin high level
voltage
0.7V
DD
-V
DD
V
V
LSEL
OSC32_IN input pin low level voltage V
SS
-0.3V
DD
t
w(LSEH)
t
w(LSEL)
OSC32_IN high or low time
(1)
450 - -
ns
t
r(LSE)
t
f(LSE)
OSC32_IN rise or fall time
(1)
--50
C
in(LSE)
OSC32_IN input capacitance
(1)
--5-pF
DuCy
(LSE)
Duty cycle - 30 - 70 %
I
L
OSC32_IN Input leakage current V
SS
≤ V
IN
≤ V
DD
--±1µA
1. Guaranteed by design.
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