Datasheet

STM32F051x Electrical characteristics
Doc ID 022265 Rev 3 57/105
6.3.6 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 GPIO.
The external clock signal has to respect the I/O characteristics in Section 6.3.13. However,
the recommended clock input waveform is shown in Figure 12.
Figure 12. High-speed external clock source AC timing diagram
Table 34. High-speed external user clock characteristics
Symbol Parameter
(1)
1. Guaranteed by design, not tested in production.
Conditions Min Typ Max Unit
f
HSE_ext
User external clock source
frequency
1832MHz
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(HSEH)
t
w(HSEL)
OSC_IN high or low time 15 - -
ns
t
r(HSE)
t
f(HSE)
OSC_IN rise or fall time - - 20
-36
6
(3%(
T
F(3%


4
(3%
T
T
R(3%
6
(3%,
T
7(3%(
T
7(3%,