SX1281
2.4GHz LoRa/FLRC/(G)FSK · +12.5 dBm TX · Built-in Ranging (RToF) · −132 dBm LoRa Sensitivity · FLRC 1.3 Mbps · QFN-24 (4×4mm) · Semtech
| Part Number | SX1281 |
|---|---|
| Manufacturer | Semtech |
| Type | 2.4GHz RF Transceiver (LoRa/FLRC/FSK) |
| Frequency Range | 2.4 GHz ISM Band (2400–2500 MHz) |
| Modulation | LoRa, FLRC, (G)FSK |
| Max TX Power | +12.5 dBm (configurable) |
| LoRa Sensitivity | −132 dBm (SF12, BW 203 kHz) |
| FLRC Sensitivity | −104 dBm (1 Mbps, 2-FSK) |
| RX Current (LoRa) | 8.2 mA typical |
| TX Current | 24 mA at +12.5 dBm |
| FLRC Max Data Rate | 1.3 Mbps (GFSK, 1.6 MHz BW) |
| LoRa Spreading Factor | SF5 – SF12 |
| Ranging Engine | RToF (Round-Trip Time-of-Flight), ±1m accuracy |
| Package | QFN-24 (4×4mm) |
| Supply Voltage | 1.8 V – 3.7 V |
| Operating Temperature | −40°C to +85°C |
| Supply Voltage (VDD) | 1.8 V – 3.7 V |
|---|---|
| TX Current (@ +12.5 dBm) | 24 mA typical |
| TX Current (@ +10 dBm) | 18 mA typical |
| RX Current (LoRa) | 8.2 mA typical |
| RX Current (FLRC) | 7.5 mA typical |
| Sleep Current | 0.6 µA (warm start) |
| Output Power Range | −18 to +12.5 dBm (programmable) |
| FLRC Data Rates | 260 kbps, 520 kbps, 1 Mbps, 1.3 Mbps |
| LoRa Bandwidth Options | 203, 406, 812, 1625 kHz |
| Ranging Precision | ±1 m (typical, line-of-sight) |
| Digital Interface | 4-wire SPI (up to 18 MHz SCLK) |
|---|---|
| Logic Level | 1.8V – 3.7V (VDDIO domain) |
| GPIO Pins | 3 configurable DIO lines (DIO1, DIO2, DIO3) |
| Antenna Interface | Single-ended 50Ω RF port (direct antenna match) |
| Busy Pin | Yes — hardware command status indicator |
| Ranging Mode | Master/Slave RToF protocol with auto-acknowledge |
| Packet Engine | Hardware CRC, whitening, forward error correction |
| CAD Support | Channel Activity Detection for 2.4 GHz ISM |
| Pins | 24-pin QFN (SPI_SCK, SPI_MOSI, SPI_MISO, NSS, DIO1–3, BUSY, XTAL, VBAT, GND, etc.) |
| Part Number | SX1281 |
|---|---|
| Orderable Qty | 1 pcs – 10,000+ pcs |
| Price (1–9 pcs) | Contact for quote |
| Price (10–99 pcs) | Contact for quote |
| Price (100–499 pcs) | Contact for quote |
| Price (500+ pcs) | Best pricing available |
| Lead Time (stock) | 3–7 business days |
| Packaging | Tape & Reel (T&R) |
| RoHS Compliant | Yes (Pb-free) |
Please confirm exact parameters with manufacturer datasheet.
The SX1281 is a unique RF transceiver from Semtech — it remains the only LoRa-capable IC designed specifically for the 2.4 GHz ISM band. Housed in a compact QFN-24 (4×4mm) package, it supports three distinct modulation modes: LoRa for long-range robustness, FLRC for high-speed data at up to 1.3 Mbps, and legacy (G)FSK for interoperability. This multi-mode versatility makes it the undisputed RF foundation of the ExpressLRS (ELRS) open-source RC protocol.
What truly distinguishes the SX1281 is its integrated RToF (Round-Trip Time-of-Flight) ranging engine, capable of ±1 meter precision over hundreds of meters. This hardware-level distance measurement enables drone-to-drone relative positioning, swarm coordination, and TDoA-based locating — all without requiring a separate GPS module. For commercial drone fleets operating in GPS-denied environments, this is a critical capability that no other 2.4 GHz transceiver in its class provides.
In the UAV racing and freestyle world, the SX1281 is synonymous with ExpressLRS. Its FLRC mode at 1.3 Mbps provides enough throughput for basic HD video streaming, while the LoRa mode at longer ranges delivers payload telemetry and auxiliary sensor data. The transceiver achieves packet rates exceeding 500 Hz in ExpressLRS 500Hz mode — a requirement for top-tier racing pilots who demand sub-millisecond control latency.
With −132 dBm LoRa sensitivity at SF12, the SX1281 pushes the range envelope for 2.4 GHz links far beyond traditional FSK transceivers like the CC2500 or NRF24L01. Combined with fast channel switching and interference avoidance algorithms built into ExpressLRS firmware, it delivers a rock-solid RC link even in heavily congested 2.4 GHz environments such as racing events with dozens of simultaneous pilots.
Key Features
- Only LoRa IC for the 2.4 GHz ISM band — unique in the industry
- Three modulation modes: LoRa (range), FLRC (speed), and (G)FSK (compatibility)
- Built-in RToF ranging engine with ±1 m accuracy for drone positioning
- FLRC mode delivers up to 1.3 Mbps — usable for basic HD video downlink
- −132 dBm LoRa sensitivity for extended 2.4 GHz range far beyond FSK
- Hardware foundation of ExpressLRS protocol with 500 Hz+ packet rates
- Fast SPI interface up to 18 MHz for minimal MCU overhead
- 0.6 µA sleep current for ultra-low power standby
Building ExpressLRS or 2.4GHz UAV RC Hardware?
Get genuine SX1281 from UAVCHIP with competitive pricing and global express delivery.
The SX1281 is in active production at Semtech with strong demand from ExpressLRS hardware manufacturers and UAV OEMs. UAVCHIP sources directly through authorized Semtech distribution channels with full lot traceability. Every shipment includes factory-original moisture barrier packaging with humidity indicator cards for proper MSL handling.
Key considerations for SX1281 procurement: verify the date code for latest silicon revision (newer lots include improved ranging firmware), ensure ESD-safe handling (the QFN-24 package is sensitive to static discharge), and confirm reel integrity for volume production. UAVCHIP provides sample testing support for customers qualifying the SX1281 in new ExpressLRS or proprietary designs.
- Factory-sealed MSL-3 tape & reel packaging with desiccant and HIC card
- Full batch traceability to Semtech wafer fabrication records
- ESD-safe storage and handling per IEC 61340-5-1 throughout warehouse operations
- Flexible order quantities from 1 sample to 10,000+ production units
- Global DHL/FedEx priority shipping with export documentation