Datasheet

Electrical characteristics STM32F051x4 STM32F051x6 STM32F051x8
60/121 DocID022265 Rev 6
Figure 15. High-speed external clock source AC timing diagram
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 res
pect the I/O characteristics in Section 6.3.14. However,
the recommended clock input waveform
is shown in Figure 16.
Figure 16. Low-speed external clock source AC timing diagram
1. Guaranteed by design, not tested in production.
Table 34. Low-speed external user clock characteristics
Symbol Parameter
(1)
1. Guaranteed by design, not tested in production.
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
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