STM32F070CB datasheet(49/83 Pages) STMICROELECTRONICS

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STM32F070CB/RB/C6/F6

Electrical characteristics

obtained with typical external components specified in Table 33. 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).

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 14. 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.

Table 33. LSE oscillator characteristics (fLSE = 32.768 kHz)

Symbol

Parameter

Conditions(1)

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

design guide for ST microcontrollers”.

Min(2)

Typ

Max(2)

2. Guaranteed by design, not tested in production.

Unit

IDD

LSE current

consumption

low drive capability

0.5

0.9

µA

medium-low drive capability

medium-high drive capability

1.3

high drive capability

1.6

Oscillator

transconductance

low drive capability

µA/V

medium-low drive capability

medium-high drive capability

high drive capability

tSU(LSE)(3)

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

Startup time

VDDIOx is stabilized

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