ST10F273E datasheet(153/179 Pages) STMICROELECTRONICS

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ST10F273E

Electrical characteristics

153/179

The given values of CA do not include the stray capacitance of the package and of the

printed circuit board: the negative resistance values are calculated assuming additional 5pF

to the values in the table. The crystal shunt capacitance (C0), the package and the stray

capacitance between XTAL1 and XTAL2 pins is globally assumed equal to 4pF.

The external resistance between XTAL1 and XTAL2 is not necessary, since already present

on the silicon.

24.8.12

32 kHz oscillator specifications

VDD = 5V ± 10%, VSS = 0V, TA = –40°C to +125°C

Figure 46.

32 kHz crystal oscillator connection diagram

The given values of CA do not include the stray capacitance of the package and of the

printed circuit board: the negative resistance values are calculated assuming additional 5pF

to the values in the table. The crystal shunt capacitance (C0) and the package capacitance

between XTAL3 and XTAL4 pins is globally assumed equal to 4pF. The external resistance

between XTAL3 and XTAL4 is not necessary, since already present on the silicon.

Table 74.

32 kHz oscillator characteristics

Symbol

Parameter

Conditions

Value

Unit

Min.

Typ.

Max.

gm32

Oscillator transconductance(1)

At power-on a high current biasing is applied for faster oscillation start-up. Once the oscillation is started,

the current biasing is reduced to lower the power consumption of the system.

Start-up

µA/V

Normal run

VOSC32

Oscillation amplitude(2)

Not 100% tested, guaranteed by design characterization.

Peak to peak

0.5

1.0

2.4

VAV32

Oscillation voltage level (2)

Sine wave middle

0.7

0.9

1.2

tSTUP32

Oscillator start-up time (2)

Stable VDD

–15

Table 75.

Minimum values of negative resistance (module) for 32 kHz oscillator

CA = 6pF

CA = 12pF CA = 15pF CA = 18pF CA = 22pF CA = 27pF CA = 33pF

32 kHz

----

150 k

Ω

120 k

Ω

90 kW

crystal

ST10F273E

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