STA8090WG datasheet(28/34 Pages) STMICROELECTRONICS

28 / 34 page

Electrical characteristics

STA8090WG

28/34

DS11052 Rev 5

The oscillator amplifier specifications are shown in the following table:

Figure 3. 32.768 kHz crystal connection

To drive the 32.768 kHz crystal pins from an external clock source:



Disable the oscillator (bit28-OSCI_EN = 0b in PRCC_BACKUP_REG0 register). This

disables the internal inverter, thus reducing the power consumption to minimum. This

also allows to drive RTC_XTI input even when a crystal is connected between

RTC_XTI and RTC_XTO pins.



Drive the RTC_XTI pin with a square signal or a sine wave.

CMSXTAL

Motional capacitance(1)

–5.0

–

COSXTAL

Shunt capacitance(1)

–1.3

–

ESR

Resonance resistance(1)

––

kΩ

External load capacitance(1)

–18

–

1. Not tested in production.

Table 25. Oscillator amplifier specifications

Symbol

Parameter

Min.

Typ.

Max.

Unit

Startup time(1)

1. Not tested in production.

0.2

0.3

0.6

Drive level(1)

––

<0.1

µW

RLC

Required load capacitance(1)

–

12.5

–

Startup transconductance

22.5

33.6

–

µA/V

Table 26. Characteristics of external slow clock input

Symbol

Parameter

Min.

Typ.

Max.

Unit

TJIT (cc)

Cycle-to-cycle jitter

-70

–

TJIT (per)

Period jitter

-70

–

Table 24. Crystal recommended specifications (continued)

Symbol

Parameter

Min.

Typ.

Max.

Unit

CL =18pF

CL = 18 pF

32.768 kHz

Crystal

RTC_XTI

RCT_XTO

Device

GAPG0906151525PS

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