SI4460-C2A-GM Datasheet, PDF (41/53 Pages) Silicon Laboratories – HIGH-PERFORMANCE, LOW-CURRENT TRANSCEIVER

Si4463/61/60-C
Figure 16. RX and TX LDC Sequences
The basic operation of RX LDC mode is shown in Figure 17. The receiver periodically wakes itself up to work on
RX_STATE during LDC mode duration. If a valid preamble is not detected, a receive error is detected, or an entire
packet is not received, the receiver returns to the WUT state (i.e., ready or sleep) at the end of LDC mode duration
and remains in that mode until the beginning of the next wake-up period. If a valid preamble or sync word is
detected, the receiver delays the LDC mode duration to receive the entire packet. If a packet is not received during
two LDC mode durations, the receiver returns to the WUT state at the last LDC mode duration until the beginning
of the next wake-up period.
Figure 17. Low Duty Cycle Mode for RX
In TX LDC mode, the transmitter periodically wakes itself up to transmit a packet that is in the data buffer. If a
packet has been transmitted, nIRQ goes low if the option is set in the INT_CTL_ENABLE property. After
transmitting, the transmitter immediately returns to the WUT state and stays there until the next wake-up time
expires.
8.3. Temperature, Battery Voltage, and Auxiliary ADC
The Si446x family contains an integrated auxiliary ADC for measuring internal battery voltage, an internal
temperature sensor, or an external component over a GPIO. The ADC utilizes a SAR architecture and achieves
11-bit resolution. The Effective Number of Bits (ENOB) is 9 bits. When measuring external components, the input
voltage range is 1 V, and the conversion rate is between 300 Hz to 2.44 kHz. The ADC value is read by first
sending the GET_ADC_READING command and enabling the inputs that are desired to be read: GPIO, battery, or
temp. The temperature sensor accuracy at 25 °C is typically ±2 °C. Refer to API documentation for details on the
command and reply stream.
8.4. Low Battery Detector
The low battery detector (LBD) is enabled and utilized as part of the wake-up-timer (WUT). The LBD function is not
available unless the WUT is enabled, but the host MCU can manually check the battery voltage anytime with the
auxiliary ADC. The LBD function is enabled in the GLOBAL_WUT_CONFIG API property. The battery voltage will
be compared against the threshold each time the WUT expires. The threshold for the LBD function is set in
GLOBAL_LOW_BATT_THRESH. The threshold steps are in increments of 50 mV, ranging from a minimum of
1.5 V up to 3.05 V. The accuracy of the LBD is ±3%. The LBD notification can be configured as an interrupt on the
nIRQ pin or enabled as a direct function on one of the GPIOs.
Rev 1.0
41