Datasheet

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STM32F303xB STM32F303xC Electrical characteristics
118
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 GPIO. The
external clock signal has to respect the I/O characteristics in Section 6.3.14. However, the
recommended clock input waveform is shown in Figure 14
Figure 14. Low-speed external clock source AC timing diagram
Table 39. Low-speed external user clock characteristics
Symbol Parameter Conditions Min Typ Max Unit
f
LSE_ext
User External clock source
frequency
(1)
1. Guaranteed by design, not tested in production.
- 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
MS19215V2
V
LSEH
t
f(LSE)
90%
10%
T
LSE
t
t
r(LSE)
V
LSEL
t
W(LSEH)
t
W(LSEL)