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 84
SX1272/73
WIRELESS, SENSING & TIMING DATASHEET
Rev. 2 - July 2014
©2014 Semtech Corporation
5.4.4. Over Current Protection
The power amplifiers of SX1272/73 are protected against current over supply in adverse RF load conditions by the over
current protection block. This has the added benefit of protecting battery chemistries with limited peak current capability
and minimising worst case PA consumption in battery life calculations. The current limiter value is controlled by the
OcpTrim bits in RegOcp and is calculated according to the following formulas:
Table 35 Trimming of the OCP Current
Note Imax sets a limit on the current drain of the Power Amplifier only, hence the maximum current drain of the SX1272/
73 is equal to Imax + I
FS
.
5.5. Receiver Description
5.5.1. Overview
The SX1272/73 features a digital receiver with the analog to digital conversion process performed directly following the
LNA-Mixer block. In addition to the LoRa
TM
modulation scheme the low-IF receiver is able to demodulate ASK, OOK,
(G)FSK and (G)MSK modulation. All filtering, demodulation, gain control, synchronization and packet handling is
performed digitally allowing a high degree of programmable flexibility. The receiver also has automatic gain calibration, this
improves the precision of RSSI measurement and enhances image rejection.
5.5.2. Receiver Enabled and Receiver Active States
In the receiver operating mode two states of functionality are defined. Upon initial transition to receiver operating mode the
receiver is in the ‘receiver-enabled’ state. In this state the receiver awaits for either the user defined valid preamble or RSSI
detection criterion to be fulfilled. Once met the receiver enters ‘receiver-active’ state. In this second state the received
signal is processed by the packet engine and top level sequencer. For a complete description of the digital functions of the
SX1272/73 receiver please see Section
5.5 of the datasheet.
OcpTrim
I
MAX
Imax Formula
0 to 15
45 to 120 mA 45 + 5*OcpTrim [mA]
16 to 27
130 to 240 mA -30 + 10*OcpTrim [mA]
27+
240 mA 240 [mA]