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 44
SX1272/73
WIRELESS, SENSING & TIMING DATASHEET
Rev. 2 - July 2014
©2014 Semtech Corporation
4.2.2. FSK/OOK Transmission
4.2.2.1. FSK Modulation
FSK modulation is performed inside the PLL bandwidth by changing the fractional divider ratio in the feedback loop of the
PLL. The high resolution of the sigma-delta modulator allows for very narrow frequency deviation. The frequency deviation
F
DEV
is given by:
To ensure correct modulation the following limit applies:
Note No constraint applies to the modulation index of the transmitter, but the frequency deviation must be set between
600 Hz and 200 kHz.
4.2.2.2. OOK Modulation
OOK modulation is applied by switching on and off the power amplifier. Digital control and ramping are available to improve
the transient power response of the OOK transmitter.
4.2.2.3. Modulation Shaping
Modulation shaping can be applied in both OOK and FSK modulation modes to improve the narrowband response of the
transmitter. Both shaping features are controlled with PaRamp bits in RegPaRamp.
In FSK mode, a Gaussian filter with BT = 0.5 or 1 can be used to filter the modulation stream, at the input of the sigma-
delta modulator. If the Gaussian filter is enabled when the SX1272/73 is in Continuous mode, DCLK signal on pin 10
(DIO1/DCLK) will trigger an interrupt on the uC each time a new bit has to be transmitted. Please refer to section
4.2.13.2 for details.
When OOK modulation is used the PA bias voltages are ramped up and down smoothly when the PA is turned on and
off to reduce spectral splatter.
Round bit rates
(multiples of 12.5, 25 and
50 kbps)
0x0A 0x00 12.5 kbps 12.5 kbps 12500.00
0x05 0x00 25 kbps 25 kbps 25000.00
0x80 0x00 50 kbps 50000.00
0x01 0x40 100 kbps 100000.0
0x00 0xD5 150 kbps 150234.7
0x00 0xA0 200 kbps 200000.0
0x00 0x80 250 kbps 250000.0
0x00 0x6B 300 kbps 299065.4
Watch Xtal frequency 0x03 0xD1 32.768 kbps 32.768 kbps 32753.32
Type
BitRate
(15:8)
BitRate
(7:0)
(G)FSK
(G)MSK
OOK
Actual BR
(b/s)
F
DEV
F
STEP
Fdev 13 0(,)×=
F
DEV
BR
2
-------
250()kHz≤+