STA8090EXGA datasheet(36/42 Pages) STMICROELECTRONICS

36 / 42 page

Electrical characteristics

STA8090EXGA

36/42

DS11733 Rev 3

Figure 2. 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.



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

4.8.3

OSCI oscillator specifications

The supported values of the embedded BOOT ROM are 16.368 MHz, 24.00 MHz,

26.00 MHz and 48.00 MHz.

The default values supported by the GNSS binary image are 26 MHz and 48 MHz, to enable

USB peripheral the 48 MHz is mandatory.

4.8.4

ADC specifications

This section gives the AC specification of the 10 bit Successive Approximation Register

ADC embedded in STA8090EXGA device. It is controlled by the ARM9 MCU through a

wrapper and an APB bridge as depicted in Figure 3 and it has a maximum conversion rate

of 1MSPS with 8 muxed analog input channels capability. An internal voltage reference is

used and analog/digital power supplies connections are implemented inside the device

without any needs of dedicated external pins.

Table 29. Characteristics of external slow clock input

Symbol

Parameter

Min.

Typ.

Max.

Unit

TJIT (cc)

Cycle-to-cycle jitter

-70

—

TJIT (per)

Period jitter

-70

—

Variation

-500

—

500

ppm

TDUTY

Duty cycle

—

CL = 18 pF

32.768 kHz

Crystal

RTC_XTII

RCT_XTO

Device

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