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 82
SX1272/73
WIRELESS, SENSING & TIMING DATASHEET
Rev. 2 - July 2014
©2014 Semtech Corporation
5.4. Transmitter Description
The transmitter of SX1272/73 comprises the frequency synthesizer, modulator (both LoRa
TM
and FSK/OOK) and power
amplifier blocks, together with the DC biasing and ramping functionality that is provided through the VR_PA block.
5.4.1. Architecture Description
The architecture of the RF front end is shown in the following diagram. Here we see that the unregulated PA0 is connected
to the RFO pin features a single low power amplifier device. The PA_BOOST pin is connected to the internally regulated
PA1 and PA2 circuits. Here PA2 is a high power amplifier that permits continuous operation up to +17 dBm and duty cycled
operation up to +20 dBm. For full details of operation at +20 dBm please consult Section
5.4.3.
Figure 42. RF Front-end Architecture Shows the Internal PA Configuration.
5.4.2. RF Power Amplifiers
Three power amplifier blocks, PA0 - PA2, are available in the SX1272/73. PA0 is a high efficiency amplifier capable of
yielding RF power programmable in 1 dB steps from -1 dBm to +14 dBm directly into a 50 ohm load with low current
consumption. PA0 is connected to pin RFO (pin 24).
PA1 and PA2 are both connected to pin PA_BOOST (pin 27). There are two potential configurations of these power
amplifiers, fixed or programmable. In the fixed configuration they can deliver up to +20 dBm. In programmable
configuration they can provide from +17 dBm to +2 dBm in 1 dB programmable steps. Naturally, low impedance matching
and harmonic filtering is required to ensure RF power delivery and regulatory compliance. (See the applications section of
this document for more details).
Table 31 Power Amplifier Mode Selection Truth Table
PaSelect Mode Power Range Pout Formula
0
PA0 output on pin RFO -1 to +14 dBm -1 dBm + OutputPower
1
PA1 and PA2 combined on pin PA_-
BOOST
+2 to +17 dBm +2 dBm + OutputPower
1 PA1+PA2 on PA_BOOST with high output
power +20 dBm settings (see 5.4.3)
+5 to +20 dBm +5 dBm + OutputPower
LNA
Rec eiv er Chain
RFI
Local
Os c illato r
PA 0
PA 1
PA 2
PA _ BOO S T
RFO