SI4460-C2A-GM Datasheet, PDF (40/53 Pages) Silicon Laboratories – HIGH-PERFORMANCE, LOW-CURRENT TRANSCEIVER

Si4463/61/60-C
7. RX Modem Configuration
The Si446x can easily be configured for different data rate, deviation, frequency, etc. by using the Radio
Configuration Application (RCA) GUI which is part of the Wireless Development Suite (WDS) program.
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
register. The formula for calculating the Wake-Up Period is as follows:
WUT = WUT_M  ⁴-----^-₃----₂₂---_.-^W-₇---₆^U---₈^T---^_---^R--ms
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. Refer to API documentation for details on WUT related commands and properties.
8.2. Low Duty Cycle Mode (Auto RX Wake-Up)
The low duty cycle (LDC) mode is implemented to automatically wake-up the receiver to check if a valid signal is
available or to enable the transmitter to send a packet. It allows low average current polling operation by the Si446x
for which the wake-up timer (WUT) is used. RX and TX LDC operation must be set via the
GLOBAL_WUT_CONFIG property when setting up the WUT. The LDC wake-up period is determined by the
following formula:
LDC = WUT_LDC  ⁴-----^-₃----₂₂---_.-^W-₇---₆^U---₈^T---^_---^R--ms
where the WUT_LDC parameter can be set by the GLOBAL_WUT_LDC property. The WUT period must be set in
conjunction with the LDC mode duration; for the relevant API properties, see the wake-up timer (WUT) section.
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