Electrical characteristics
STM32F042xx
DocID025832 Rev 2
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
. However,
the recommended clock input waveform is shown in
.
Figure 16. Low-speed external clock source AC timing diagram
Table 35. Low-speed external user clock characteristics
Symbol
Parameter
(1)
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
0.7
V
DDIOx
-
V
DDIOx
V
V
LSEL
OSC32_IN input pin low level voltage
V
SS
-
0.3
V
DDIOx
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
1. Guaranteed by design, not tested in production.
069
9/6(+
WI/6(
7/6(
W
WU/6(
9/6(/
WZ/6(+
WZ/6(/