Table 30. Low-Speed External User Clock Characteristics; Figure 14. Low-Speed External Clock Source Ac Timing Diagram - STMicroelectronics STM32F050G6 Manual

STM32F050xx
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
the recommended clock input waveform is shown in
Table 30.
Symbol
f
LSE_ext
V
LSEH
V
LSEL
t
w(LSEH)
t
w(LSEL)
t
r(LSE)
t
f(LSE)
1. Guaranteed by design, not tested in production.

Figure 14. Low-speed external clock source AC timing diagram

V LSEH
V LSEL
Low-speed external user clock characteristics
(1)
Parameter
User External clock source
frequency
OSC32_IN input pin high level
voltage
OSC32_IN input pin low level
voltage
OSC32_IN high or low time
OSC32_IN rise or fall time
90%
10%
t r(LSE)
Doc ID 023079 Rev 3
Figure
Conditions
t W(LSEH)
t f(LSE)
T LSE
Electrical characteristics
Section 6.3.13. However,
14.
Min Typ Max
- 32.768 1000
0.7V - V
DD DD
V - 0.3V
SS
450 - -
- - 50
t W(LSEL)
MS19215V2
Unit
kHz
V
DD
ns
t
53/98