STM32F091CB datasheet(71/127 Pages) STMICROELECTRONICS

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STM32F091xB STM32F091xC

Electrical characteristics

Note:

For information on selecting the crystal, refer to the application note AN2867 “Oscillator

design guide for ST microcontrollers” available from the ST website www.st.com.

Figure 18. Typical application with a 32.768 kHz crystal

Note:

An external resistor is not required between OSC32_IN and OSC32_OUT and it is forbidden

to add one.

6.3.8

Internal clock source characteristics

The parameters given in Table 41 are derived from tests performed under ambient

temperature and supply voltage conditions summarized in Table 24: General operating

conditions. The provided curves are characterization results, not tested in production.

Oscillator

transconductance

LSEDRV[1:0]=00

lower driving capability

µA/V

LSEDRV[1:0]= 01

medium low driving capability

LSEDRV[1:0] = 10

medium high driving capability

LSEDRV[1:0]=11

higher driving capability

tSU(LSE)(3)

Startup time

VDDIOx is stabilized

1. Refer to the note and caution paragraphs below the table, and to the application note AN2867 “Oscillator design guide for

ST microcontrollers”.

2. Guaranteed by design, not tested in production.

tSU(LSE) is the startup time measured from the moment it is enabled (by software) to a stabilized 32.768 kHz oscillation is

reached. This value is measured for a standard crystal and it can vary significantly with the crystal manufacturer

Table 40. LSE oscillator characteristics (fLSE = 32.768 kHz)

Symbol

Parameter

Conditions(1)

Min(2)

Typ

Max(2) Unit

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