Data Sheet

LC840PA
Datasheet
https://www.lairdconnect.com
28
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5.3 Clocks and Timers
5.3.1 Clocks
The integrated high accuracy 32 MHz (±10 ppm) crystal oscillator helps with radio operation and reducing power consumption in
the active modes.
The integrated on-chip 32.768 kHz LFRC oscillator (±500 ppm) provides protocol timing and helps with radio power consumption
in the system StandByDoze and Deep Sleep modes by reducing the time that the RX window needs to be open.
To keep the on-chip 32.768 kHz LFRC oscillator within ±500 ppm (which is needed to run the Bluetooth LE stack) accuracy, RC
oscillator needs to be calibrated (which takes 33 mS) regularly. The default calibration interval is eight seconds which is enough
to keep within ±500 ppm. The calibration interval ranges from 0.25 seconds to 31.75 seconds (in multiples of 0.25 seconds) and
configurable via firmware
The ProFLEX firmware does not use the on-chip 32.768kHz LFRC oscillator but instead requires an externa 32.768
crystal to be attached. The external crystal enables high baud rate communications and ensures the lowest power
operation in sleep mode.
5.3.2 Timers
When using smartBASIC, the timer subsystem enables applications to be written which allows future events to be generated
based on timeouts.
▪ Regular Timer – There are eight built-in timers (regular timers) derived from a single RTC clock which are controlled solely
by smartBASIC functions. The resolution of the regular timer is 976 microseconds.
▪ Tick Timer – A 31-bit free running counter that increments every (1) millisecond. The resolution of this counter is 488
microseconds.
Refer to the smartBASIC User Guide available from the Laird BL654PA product page.
The ProFLEX firmware uses timers as needed internally for RTOS, internal and external events and scheduling.
5.4 Radio Frequency (RF)
▪ 2402–2480 MHz Bluetooth Low Energy (Bluetooth LE) BT5.2 radio transceiver
– RX sensitivity -98.5 dBm 1Mbps Bluetooth LE
– RX sensitivity -95 dBm 2Mbps Bluetooth LE
– RX sensitivity -107 dBm 125 kbps coded PHY Bluetooth LE (long-range).
– Tx output power of +18 dBm programmable down to 14 dBm, 6 dBm, 0 dBm, -6 dBm and final TX power level of -26
dBm.
– TX power for coded PHY 125 kbps (s=8) is limited to 14 dBm to stay within regulatory TX power spectral density
requirements (Bluetooth LE only)
▪ 2405–2480 MHz IEEE 802.15.5-2006 radio transceiver, implementing IEEE 802.15.5-2006 compliant
– 250 kbps, 2450 MHz, O-QSPK PHY
– Channel 11-25, channel 11 2405 MHz and CH25 2475 MHz (CH26 not certified)
– Clear channel assessment (CCA)
– Energy detection (ED) scan
– CRC generation
MANDITORY: Please read the radio regulatory information in Note 1 and Note 2 including RF duty cycle limitations.
▪ RF band pass filter to help with cellular RF co-existence.
▪ RF conducted interface available in the following two ways:
– 453-00087: RF connected to on-board PCB trace antenna
– 453-00088: RF connected to on-board IPEX MH4 RF connector
▪ Antenna options:
– Integrated PCB trace antenna on the 453-00087
– External dipole antenna connected with to IPEX MH4 RF connector on the 453-00088
▪ Received Signal Strength Indicator (RSSI)
– RSSI accuracy (valid range -90 to -20 dBm) is ±2 dB typical
 LC840PA RX LNA gain is 11dB, so RSSI valid range becomes -101 dB to -31 dBm
– RSSI resolution 1 dB typical
▪ Maximum Received Signal Strength (at <0.1% PER) of -11 dBm. Limited by RX LNA gain of 11 dB in front end module