Datasheet

Electrical characteristics STM32L432KB STM32L432KC
92/155 DocID028798 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 6.3.14. However,
the recommended clock input waveform is shown in Figure 12.
Figure 12. Low-speed external clock source AC timing diagram
Low-speed external clock generated from a crystal resonator
The low-speed external (LSE) clock can be supplied with a 32.768 kHz crystal resonator
oscillator. All the information given in this paragraph are based on design simulation results
obtained with typical external components specified in
Table 44. In the application, the
resonator and the load capacitors have to be placed as close as possible to the oscillator
pins in order to minimize output distortion and startup stabilization time. Refer to the crystal
resonator manufacturer for more details on the resonator characteristics (frequency,
package, accuracy).
Table 43. Low-speed external user clock characteristics
(1)
Symbol Parameter 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 - 250 - - ns
1. Guaranteed by design.
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