Datasheet
Table Of Contents
- 1. General Description
- 2. Electrical Characteristics
- 3. SX1272/73 Features
- 4. SX1272/73 Digital Electronics
- 4.1. The LoRaTM Modem
- 4.2. FSK/OOK Modem
- 4.2.1. Bit Rate Setting
- 4.2.2. FSK/OOK Transmission
- 4.2.3. FSK/OOK Reception
- 4.2.4. Operating Modes in FSK/OOK Mode
- 4.2.5. General Overview
- 4.2.6. Startup Times
- 4.2.7. Receiver Startup Options
- 4.2.8. Receiver Restart Methods
- 4.2.9. Top Level Sequencer
- 4.2.10. Data Processing in FSK/OOK Mode
- 4.2.11. FIFO
- 4.2.12. Digital IO Pins Mapping
- 4.2.13. Continuous Mode
- 4.2.14. Packet Mode
- 4.2.15. io-homecontrol® Compatibility Mode
- 4.3. SPI Interface
- 5. SX1272/73 Analog & RF Frontend Electronics
- 6. Description of the Registers
- 7. Application Information
- 8. Packaging Information
- 9. Revision History
www.semtech.comPage 23
SX1272/73
WIRELESS, SENSING & TIMING DATASHEET
Rev. 2 - July 2014
©2014 Semtech Corporation
4. SX1272/73 Digital Electronics
4.1. The LoRa
TM
Modem
The LoRa
TM
modem uses spread spectrum modulation and forward error correction techniques to increase the range and
robustness of radio communication links compared to traditional FSK or OOK based modulation. Examples of the
performance improvement possible for several settings are summarised in the table below. The spreading factor and error
correction rate are design variables that allow the designer to optimise the trade-off between occupied bandwidth, data
rate, link budget improvement and immunity to interference. In the table below a coding rate of 4/5 is used.
Table 12 Example LoRa
TM
Modem Performances
Typically such performance gains require high stability frequency references, with LoRa
TM
this is not the case. Low crystal
tolerances are easily accommodated reducing the overall BoM cost for a given increase in link budget.
For European operation the range of crystal tolerances acceptable for each sub-band (of the ERC 70-03) is given in the
specifications table. For US based operation a frequency hopping mode is available that automates both the LoRa
TM
spread
spectrum and frequency hopping spread spectrum processes.
Another important facet of the LoRa
TM
modem is its increased immunity to interference. The LoRa
TM
modem is capable of
co-channel GMSK rejection of up to 25 dB. This immunity to interference permits the simple coexistence of LoRa
TM
modulated systems either in bands of heavy spectral usage or in hybrid communication networks that use LoRa
TM
to extend
range when legacy modulation schemes fail.
Bandwidth
(kHz)
Spreading Factor
Nominal Rb
(bps)
Sensitivity
(dBm)
125 6 9380 -122
125 12 293 -137
250 6 18750 -119
250 12 586 -134
500 6 3750 -116
500 12 1172 -131