STM32F078CB Datasheet, PDF (62/120 Pages) STMicroelectronics – CRC calculation unit

Electrical characteristics
STM32F078CB, STM32F078RB, STM32F078VB
Figure 14. High-speed external clock source AC timing diagram
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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 15.
Symbol
Table 35. Low-speed external user clock characteristics
Parameter⁽¹⁾
Min
Typ
Max
f_{LSE_ext} User external clock source frequency
V_LSEH OSC32_IN input pin high level voltage
V_LSEL OSC32_IN input pin low level voltage
t_w(LSEH)
t_w(LSEL)
OSC32_IN high or low time
t_r(LSE)
t_f(LSE)
OSC32_IN rise or fall time
1. Guaranteed by design, not tested in production.
-
0.7 V_DDIOx
V_SS
450
-
32.768
-
-
-
-
1000
V_DDIOx
0.3 V_DDIOx
-
50
Unit
kHz
V
ns
Figure 15. Low-speed external clock source AC timing diagram
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