EFR32BG21 Blue Gecko Wireless SoC Family Data Sheet System Overview 3.2.2 Fractional-N Frequency Synthesizer The EFR32BG21 contains a high performance, low phase noise, fully integrated fractional-N frequency synthesizer. The synthesizer is used in receive mode to generate the LO frequency for the down-conversion mixer. It is also used in transmit mode to directly generate the modulated RF carrier. The fractional-N architecture provides excellent phase noise performance, frequency resolution better than 100 Hz, and low energy consumption. The synthesizer’s fast frequency settling allows for very short receiver and transmitter wake up times to reduce system energy consumption. 3.2.3 Receiver Architecture The EFR32BG21 uses a low-IF receiver architecture, consisting of a Low-Noise Amplifier (LNA) followed by an I/Q down-conversion mixer. The I/Q signals are further filtered and amplified before being sampled by the IF analog-to-digital converter (IFADC). The IF frequency is configurable from 150 kHz to 1371 kHz. The IF can further be configured for high-side or low-side injection, provid- ing flexibility with respect to known interferers at the image frequency. The Automatic Gain Control (AGC) module adjusts the receiver gain to optimize performance and avoid saturation for excellent selec- tivity and blocking performance. The 2.4 GHz radio is calibrated at production to improve image rejection performance. Demodulation is performed in the digital domain. The demodulator performs configurable decimation and channel filtering to allow re- ceive bandwidths ranging from 0.1 to 2530 kHz. High carrier frequency and baud rate offsets are tolerated by active estimation and compensation. Advanced features supporting high quality communication under adverse conditions include forward error correction by block and convolutional coding as well as Direct Sequence Spread Spectrum (DSSS). A Received Signal Strength Indicator (RSSI) is available for signal quality metrics, for level-based proximity detection, and for RF chan- nel access by Collision Avoidance (CA) or Listen Before Talk (LBT) algorithms. An RSSI capture value is associated with each received frame and the dynamic RSSI measurement can be monitored throughout reception. 3.2.4 Transmitter Architecture The EFR32BG21 uses a direct-conversion transmitter architecture. For constant envelope modulation formats, the modulator controls phase and frequency modulation in the frequency synthesizer. Transmit symbols or chips are optionally shaped by a digital shaping filter. The shaping filter is fully configurable, including the BT product, and can be used to implement Gaussian or Raised Cosine shap- ing. Carrier Sense Multiple Access - Collision Avoidance (CSMA-CA) or Listen Before Talk (LBT) algorithms can be automatically timed by the EFR32BG21. These algorithms are typically defined by regulatory standards to improve inter-operability in a given bandwidth be- tween devices that otherwise lack synchronized RF channel access. 3.2.5 Packet and State Trace The EFR32BG21 Frame Controller has a packet and state trace unit that provides valuable information during the development phase. It features: • Non-intrusive trace of transmit data, receive data and state information • Data observability on a single-pin UART data output, or on a two-pin SPI data output • Configurable data output bitrate / baudrate • Multiplexed transmitted data, received data and state / meta information in a single serial data stream 3.2.6 Data Buffering The EFR32BG21 features an advanced Radio Buffer Controller (BUFC) capable of handling up to 4 buffers of adjustable size from 64 bytes to 4096 bytes. Each buffer can be used for RX, TX or both. The buffer data is located in RAM, enabling zero-copy operations. 3.2.7 Radio Controller (RAC) The Radio Controller controls the top level state of the radio subsystem in the EFR32BG21. It performs the following tasks: • Precisely-timed control of enabling and disabling of the receiver and transmitter circuitry • Run-time calibration of receiver, transmitter and frequency synthesizer • Detailed frame transmission timing, including optional LBT or CSMA-CA silabs.com | Building a more connected world. Rev. 1.0 | 7 Document Outline 1. Feature List 2. Ordering Information 3. System Overview 3.1 Introduction 3.2 Radio 3.2.1 Antenna Interface 3.2.2 Fractional-N Frequency Synthesizer 3.2.3 Receiver Architecture 3.2.4 Transmitter Architecture 3.2.5 Packet and State Trace 3.2.6 Data Buffering 3.2.7 Radio Controller (RAC) 3.3 General Purpose Input/Output (GPIO) 3.4 Clocking 3.4.1 Clock Management Unit (CMU) 3.4.2 Internal and External Oscillators 3.5 Counters/Timers and PWM 3.5.1 Timer/Counter (TIMER) 3.5.2 Low Energy Timer (LETIMER) 3.5.3 Real Time Clock with Capture (RTCC) 3.5.4 Back-Up Real Time Counter 3.5.5 Watchdog Timer (WDOG) 3.6 Communications and Other Digital Peripherals 3.6.1 Universal Synchronous/Asynchronous Receiver/Transmitter (USART) 3.6.2 Inter-Integrated Circuit Interface (I2C) 3.6.3 Peripheral Reflex System (PRS) 3.7 Security Features 3.7.1 Standard Security 3.7.2 True Random Number Generator 3.8 Analog 3.8.1 Analog Comparator (ACMP) 3.8.2 Analog to Digital Converter (ADC) 3.9 Reset Management Unit (RMU) 3.10 Core and Memory 3.10.1 Processor Core 3.10.2 Memory System Controller (MSC) 3.10.3 Linked Direct Memory Access Controller (LDMA) 3.11 Memory Map 3.12 Configuration Summary 4. Electrical Specifications 4.1 Electrical Characteristics 4.1.1 Absolute Maximum Ratings 4.1.2 General Operating Conditions 4.1.3 Thermal Characteristics 4.1.4 Current Consumption 4.1.4.1 MCU current consumption at 1.8V 4.1.4.2 MCU current consumption at 3.0V 4.1.4.3 Radio current consumption at 1.8V 4.1.4.4 Radio current consumption at 3.0V 4.1.5 2.4 GHz RF Transceiver Characteristics 4.1.5.1 RF Transmitter Characteristics 4.1.5.2 RF Receiver Characteristics 4.1.6 Flash Characteristics 4.1.7 Wake Up, Entry, and Exit times 4.1.8 Oscillators 4.1.8.1 High Frequency Crystal Oscillator 4.1.8.2 Low Frequency Crystal Oscillator 4.1.8.3 High Frequency RC Oscillator (HFRCO) 4.1.8.4 Fast Start_Up RC Oscillator (FSRCO) 4.1.8.5 Low Frequency RC Oscillator 4.1.8.6 Ultra Low Frequency RC Oscillator 4.1.9 GPIO Pins (3V GPIO pins) 4.1.10 Analog to Digital Converter (ADC) 4.1.11 Analog Comparator (ACMP) 4.1.12 Temperature Sense 4.1.13 Brown Out Detectors 4.1.13.1 DVDD BOD 4.1.13.2 LE DVDD BOD 4.1.13.3 AVDD and VIO BODs 4.1.14 SPI Electrical Specifications 4.1.14.1 SPI Master Timing 4.1.14.2 SPI Slave Timing 4.1.15 I2C Electrical Specifications 4.1.15.1 I2C Standard-mode (Sm) 4.1.15.2 I2C Fast-mode (Fm) 4.1.15.3 I2C Fast-mode Plus (Fm+) 4.2 Typical Performance Curves 4.2.1 Supply Current 4.2.2 2.4 GHz Radio 5. Typical Connection Diagrams 5.1 Power 5.2 RF Matching Networks 5.2.1 2.4 GHz 0 dBm Matching Network 5.2.2 2.4 GHz 10 dBm Matching Network 5.2.3 2.4 GHz 20 dBm Matching Network 5.3 Other Connections 6. Pin Definitions 6.1 QFN32 2.4GHz Device Pinout 6.2 Alternate Function Table 6.3 Analog Peripheral Connectivity 6.4 Digital Peripheral Connectivity 7. QFN32 Package Specifications 7.1 QFN32 Package Dimensions 7.2 QFN32 PCB Land Pattern 7.3 QFN32 Package Marking 8. Revision History
