1. Product description
The SX1278/SX1276 is a long-range, low-power wireless transceiver launched by Semtech in 2013. It is a high-performance IoT wireless transceiver with a special LoRa modulation, which increases the communication range to some extent.
2. Comparison analysis
Chip package, pins
The SX1278 and SX1276 are packaged in the way, both are packaged in 6x6mm and 28-pin QFN. With a large chip size and radio frequency peripherals, the RF module size is also large. There are only two pins are different, the 21st and 22nd pins of SX1278 are GND, while the 21st pin of the SX1276 is RFI_HF and the 22nd pin is RFO_HF.
The package of SX1262 is 4x4mm, 24-pin QFN. The chip size is small, so RF modules size is also small. Pins are shown below.
Both SX1262 and SX1278/6 have a variety of modulation methods, including LoRa and traditional (G) FSK modulation. LoRa modulation itself is the highlight of these three chips.
》Crystal oscillator circuit and supporting frequency band
Both the SX1262 and SX1278/6 can use the TCXO crystal oscillator. If the TCXO crystal oscillator is used, the XTB pin is not connected. However, the 6th pin (DIO3) of the SX1262 can be used to power the TCXO crystal oscillator. It only requires software configuration.
When using XTAL, SX1278/6 need to add external matching capacitors; but SX1262 does not need, can be adjusted directly through the software.
The SX1278 supports frequency 137-525MHz, the RF transmitting output pin is pin 27(PA_BOOST) or pin 28(RFO_LF), the RF receiving input pin is pin 1(RFI_LF). The SX1276 supports frequency 137-1020 MHz, when using 137-525MHz, the RF transmitting output pin must be pin 27(PA_BOOST) or pin 28(RFO_LF), the RF receiving input pin must be pin 1(RFI_LF), when using 862-1020MHz, the RF transmitting output pin must be pin 27(PA_BOOST) or pin 22(RFO_HF), the RF receiving input pin must be pin 21(RFI_HF). From this point of view, the SX1276 can be understood as an enhanced version of the SX1278.
The SX1262 supports frequency 150-960 MHz, the RF transmitting output pin is pin 23(RFO), and the RF receiving input pins are pin 21(RFI_P) and pin 22(RFI_N). When changing the frequency band, there is no need to replace the pin, adjust the RF circuit parameters.
》Power supply and transmitting power, receiving sensitivity, current
The SX1278/6 has only one power supply mode, the maximum transmitting power is 20dBm. To achieve the maximum transmitting power, the 27th pin (PA_BOOST) must be used, and the emission current is 120mA@20dBm.
The SX1262 has a maximum transmitting power of 22dBm and has two power supply modes, a low-dropout regulator (LDO) and a high-efficiency step-down DC-DC converter. In the DC-DC mode, the emission current is 118mA@22dBm.
The receiving current of SX1278/6 is about 12mA, in the DC-DC mode, the receiving current of SX1262 is about 5mA. The highest sensitivity of the three is -148dBm.
》Spreading factor, airdata rate
Under LoRa modulation, the SX1278/6 has a spreading factor of 6-12, BW of 7.8-500 kHz, and an airdata rate of 0.018-37.5 kbps. The SX1262 has a spreading factor of 5-12, BW 7.81-500kHz and an airdata rate of 0.018-62.5kbps. It shows that under LoRa modulation, the SX1262 can have much higher airdata rate than the SX1278/6.
3. The conclusion
Through the above simple comparison, it can be seen that the SX1262 is more powerful and has advantages in terms of size. It is believed that more and more companies will prefer SX1262.