SI4464 datasheet(41/56 Pages) SILABS

41 / 56 page

Si4464/63/61/60

Rev 1.2

7. RX Modem Configuration

The Si446x can easily be configured for different data rate, deviation, frequency, etc. by using the WDS settings

calculator, which generates an initialization file for use by the host MCU.

8. Auxiliary Blocks

8.1. Wake-up Timer and 32 kHz Clock Source

The chip contains an integrated wake-up timer that can be used to periodically wake the chip from sleep mode. The

wake-up timer runs from either the internal 32 kHz RC Oscillator, or from an external 32 kHz XTAL.

The wake-up timer can be configured to run when in sleep mode. If WUT_EN = 1 in the GLOBAL_WUT_CONFIG

property, prior to entering sleep mode, the wake-up timer will count for a time specified defined by the

GLOBAL_WUT_R and GLOBAL_WUT_M properties. At the expiration of this period, an interrupt will be generated

on the nIRQ pin if this interrupt is enabled in the INT_CTL_CHIP_ENABLE property. The microcontroller will then

need to verify the interrupt by reading the chip interrupt status either via GET_INT_STATUS or a fast response

The RC oscillator frequency will change with temperature; so, a periodic recalibration is required. The RC oscillator

is automatically calibrated during the POWER_UP command and exits from the Shutdown state. To enable the

recalibration feature, CAL_EN must be set in the GLOBAL_WUT_CONFIG property, and the desired calibration

period should be selected via WUT_CAL_PERIOD[2:0] in the same API property. During the calibration, the

32 kHz RC oscillator frequency is compared to the 30 MHz XTAL and then adjusted accordingly. The calibration

needs to start the 30 MHz XTAL, which increases the average current consumption; so, a longer CAL_PERIOD

results in a lower average current consumption. The 32 kHz XTAL accuracy is comprised of both the XTAL

parameters and the internal circuit. The XTAL accuracy can be defined as the XTAL initial error + XTAL aging +

XTAL temperature drift + detuning from the internal oscillator circuit. The error caused by the internal circuit is

typically less than 10 ppm.

WUT

WUT_M

WUT_R

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32 768

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SI4464 Fiches technique(PDF) 41 Page - Silicon Laboratories