Datasheet

Electrical characteristics STM32F051x
58/105 Doc ID 022265 Rev 3
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 6.3.13. However,
the recommended clock input waveform is shown in Figure 13.
Figure 13. Low-speed external clock source AC timing diagram
Table 35. Low-speed external user clock characteristics
Symbol Parameter
(1)
1. Guaranteed by design, not tested in production.
Conditions Min Typ Max Unit
f
LSE_ext
User External clock source
frequency
- 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 450 - -
ns
t
r(LSE)
t
f(LSE)
OSC32_IN rise or fall time - - 50
-36
6
,3%(
T
F,3%


4
,3%
T
T
R,3%
6
,3%,
T
7,3%(
T
7,3%,