The **AX-SFEU-API** is a high-performance, ultra-low-power **Sigfox® Verified** transceiver System-on-Chip (SoC) designed by ON Semiconductor (now under the **onsemi** brand). It is specifically engineered for the European market (RC1 region), operating in the 868 MHz ISM band. --- ## 1. Core Technical Specifications The AX-SFEU-API integrates a micro-controller and a radio transceiver into a single package, making it ideal for miniaturized IoT devices. | Feature | Specification | | :--- | :--- | | **Frequency Band** | 868 MHz (Europe / RC1) | | **Modulation** | DBPSK (TX), GFSK (RX) | | **TX Power** | Up to +14 dBm | | **RX Sensitivity** | -126 dBm @ 600 bps | | **Interface** | SPI, UART, GPIO | | **Supply Voltage** | 1.8V to 3.6V | | **Package** | QFN40 (7mm x 5mm) | --- ## 2. Key Internal Components ### A. The Radio Transceiver The radio is the heart of the chip. It is designed for **Ultra-Narrow Band (UNB)** communication, which is the foundation of the Sigfox network. * **High Selectivity:** It can filter out noise effectively, which is crucial for long-range communication. * **Low Power Consumption:** In "Deep Sleep" mode, it consumes as little as **100 nA**, which allows sensors to run on a small battery for 5–10 years. ### B. Integrated Microcontroller The "API" suffix indicates that the chip allows the user to program their own application code directly onto the internal microcontroller. * **Memory:** Includes Flash and RAM for user applications. * **Processing:** Handles the Sigfox protocol stack internally, so you don't need an external MCU to manage the network connection. ### C. Power Management Unit (PMU) It features an integrated voltage regulator and management system that allows the chip to operate directly from a single lithium battery (like a CR2032 or Li-SOCl2). --- ## 3. Peripheral Connectivity To interact with sensors and other hardware, the AX-SFEU-API provides several I/O options: * **ADC (Analog-to-Digital Converter):** For reading analog sensors like temperature or humidity. * **GPIOs:** For controlling LEDs, switches, or waking up the chip from external events. * **Timers:** Used for scheduling transmissions or periodic sensor readings. --- ## 4. Typical Application Circuit When designing a PCB with the AX-SFEU-API, you generally need the following external components: 1. **Antenna:** Usually a 50Ω PCB trace or a whip antenna. 2. **Matching Network:** A set of inductors and capacitors (L-C circuit) to tune the radio output to the antenna. 3. **Crystal Oscillator:** Typically a TCXO (Temperature Compensated Crystal Oscillator) is required to ensure frequency stability, which is vital for the narrow-band Sigfox signal. 4. **Decoupling Capacitors:** To stabilize the power supply. ---