The **AX-SFJK-API** is a specialized System-on-Chip (SoC) or module component, typically associated with the **Sigfox** wireless communication standard. It is designed for Ultra-Low Power (ULP) Internet of Things (IoT) applications, specifically targeting the Japanese market (RCZ 3). --- ## 1. Core Technical Specifications The device acts as a single-chip solution for a Sigfox node, integrating both the radio transceiver and the microcontroller functionality. | Feature | Specification | | :--- | :--- | | **Frequency Band** | 923.2 MHz (RCZ 3 - Japan) | | **Data Rate** | 100 bps / 600 bps | | **Modulation** | DBPSK (Upstream), GFSK (Downstream) | | **Operating Voltage** | 1.8V to 3.6V | | **Interface** | UART (AT Command Set) | | **Package** | Typically QFN20 or specialized module form | --- ## 2. Key Electronic Components & Subsystems ### A. The Radio Transceiver The heart of the chip is a high-performance, narrow-band sub-GHz transceiver. * **Sensitivity:** Extremely high sensitivity (approx. -126 dBm) to allow for long-range communication despite low power output. * **Output Power:** Adjustable up to +13 dBm to comply with Japanese radio regulations while maximizing range. ### B. Microcontroller (MCU) Core The "API" suffix indicates that the chip allows users to embed their own application code directly onto the integrated MCU, rather than just using it as a "dumb" modem. * **Architecture:** Typically based on a low-power 8-bit or 32-bit RISC core. * **Memory:** Includes internal Flash and RAM to store the Sigfox stack and user application logic. ### C. Power Management Unit (PMU) Designed for battery-operated devices (often lasting 5-10 years on a single cell). * **Deep Sleep Current:** Usually in the range of **100 nA to 1.5 μA**. * **TX/RX Current:** Optimized to stay under 40mA during active transmission. --- ## 3. Peripheral Interfaces To interact with sensors and other hardware, the AX-SFJK-API provides several I/O options: * **GPIOs:** For triggering wakes or controlling LEDs/switches. * **ADC (Analog to Digital Converter):** For reading analog sensors like thermistors or light sensors. * **Timers:** Essential for scheduling periodic "heartbeat" transmissions. * **UART:** The primary communication bus for external controllers if used in "Modem Mode." --- ## 4. Application Circuitry Requirements When designing a PCB for this part, the following external electronic components are typically required: 1. **Matching Network:** A combination of inductors and capacitors to match the antenna impedance (50 ohms). 2. **TCXO (Temperature Compensated Crystal Oscillator):** Crucial for Sigfox due to the ultra-narrowband nature; frequency stability is vital to prevent signal drift. 3. **Decoupling Capacitors:** Standard 100nF and 10uF capacitors to stabilize the power supply pins.