STM32L432KB datasheet(88/149 Pages) STMICROELECTRONICS

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Electrical characteristics

STM32L432KB STM3L432KC

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DocID028798 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 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 43. 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 42. Low-speed external user clock characteristics(1)

Symbol

Parameter

Conditions

Min

Typ

Max

Unit

fLSE_ext User external clock source frequency

32.768

1000

kHz

VLSEH OSC32_IN input pin high level voltage

0.7 VDDIOx

-VDDIOx

VLSEL

OSC32_IN input pin low level voltage

VSS

-0.3 VDDIOx

tw(LSEH)

tw(LSEL)

OSC32_IN high or low time

250

1. Guaranteed by design.

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