Silicon Labs FG28 Sub-GHz wireless and 2.4 GHz BLE SoC supports Amazon Sidewalk, Wi-SUN, etc...

Silicon Labs dual-band FG28 Cortex-M33 SoC comes with sub-Gigahertz and 2.4 GHz Bluetooth LE radios that support long-range networks and protocols like Amazon Sidewalk, Wi-SUN, and other proprietary protocols, as well as a built-in AI/ML accelerator for machine learning inference and SiLabs Secure Vault technology.

The chip looks to be an update to the sub-GHz FG25 Cortex-M33 microcontroller with an additional 2.4 GHz BLE radio, but somehow less program memory (up to 256KB) and storage (up to 1024 KB). The peripherals implemented in the chip are almost the same, as the microcontroller gains support for predictive maintenance with a small matrix vector processor for AI/ML acceleration.

Silicon Labs FG28 (EFR32FG28) specifications:

MCU core – Arm Cortex-M33 @ 78 MHz with DSP instructions and FPU
On-chip memory – Up to 256 kB RAM data memory
On-chip storage – Up to 1024 kB flash program memory
AI accelerator – Matrix Vector Processor for AI/ML acceleration
Wireless
- Sub-GHz radio
  - TX power up to +20 dBm
  - Rx sensitivity
    - -98.6 dBm sensitivity @ 400 kbps 920 MHz 4-GFSK
    - -125.8 dBm sensitivity @ 4.8 kbps 915 MHz O-QPSK
    - -96.9 dBm sensitivity @ 2 Mbps 915 MHz GFSK
    - -125.3 dBm sensitivity @ 2.4 kbps 868 MHz GFSK
    - -111.5 dBm sensitivity @ 38.4 kbps 868 MHz FSK
    - -110.7 dBm sensitivity @ 100 kbps 433 MHz 2GFSK
- 2.4 GHz BLE radio – TX power up to +10 dBm
- Modulation Format
  - 2/4 (G)FSK with fully configurable shaping
  - OQPSK with DSSS
  - (G)MSK
  - OOK
- Protocol Support
  - Proprietary
  - Silicon Labs CONNECT (IEEE 802.15.4 MAC-based wireless networking stack for proprietary applications optimized for low-power devices)
  - Sidewalk
  - WM-BUS
  - Wi-SUN
  - Bluetooth Low Energy
- Energy consumption
  - 5 mA RX current at 920 MHz (400 kbps 4-FSK)
  - 4.6 mA RX current at 915 MHz (4.8 kbps O-QPSK)
  - 6.1 mA RX current at 915 MHz (2 Mbps GFSK)
  - 4.6 mA RX current at 868 MHz (2.4 kbps GFSK)
  - 4.6 mA RX current at 868 MHz (38.4 kbps FSK)
  - 4.1 mA RX current at 433 MHz (100 kbps 2GFSK)
  - 5.2 mA RX current at 2.4 GHz, 1 Mbps BLE
  - 26.2 mA TX current @ 14 dBm output power at 915 MHz (14 dBm part number)
  - 82.2 mA TX current @ 20 dBm output power at 915 MHz with (20 dBm part number)
  - 12.2 mA TX current @ 0 dBm output power, 2.4 GHz
  - 22.5 mA TX current @ 10 dBm output power, 2.4 GHz
  - Preamble Sense Mode (PSM) low-duty-cycle listen
Peripherals
- Integrated low-energy LCD controller supporting up to 192 segments
- Keypad scanner supporting up to 6 x 8 matrix (KEYSCAN)
- 2× I2C interfaces with SMBus support
- 3x Enhanced Universal Synchronous/Asynchronous Receiver/Transmitter (EUSART)
- 1x Universal Synchronous/Asynchronous Receiver/Transmitter (UART/SPI/SmartCard (ISO 7816)/IrDA/I2S)
- ADC – 12-bit @ 1 Msps, 16-bit @ 76.9 ksps
- 2x analog comparators (ACMP)
- 2-channel Digital-to-Analog Converter (VDAC)
- Low-Energy Sensor Interface (LESENSE)
- Up to 49x GPIOs with output state retention and asynchronous interrupts
- 8-channel DMA Controller
- 12-channel Peripheral Reflex System (PRS)
- 4x 16-bit Timer/Counter with 3x Compare/Capture/PWM channels
- 1x 32-bit Timer/Counter with 3x Compare/Capture/PWM channels
- 32-bit Real-Time Counter
- 24-bit Low Energy Timer for waveform generation
- 2x Watchdog Timer
- Die temperature sensor with ± 2 °C accuracy
Security – “Secure Vault” with
- Hardware Cryptographic Acceleration for AES128/192/256, ChaCha20-Poly1305, SHA-1, SHA-2/256/384/512, ECDSA, +ECDH (P-192, P-256, P-384, P-521), Ed25519 and Curve25519, J-PAKE, PBKDF2
- TRNG
- ARM TrustZone
- Secure Boot with Root of Trust and Secure Loader (RTSL)
- Secure Debug Unlock
- DPA Countermeasures
- Secure Key Management with PUF
- Anti-Tamper
- Secure Attestation
Supply Voltage – 1.71 to 3.8V DC single power supply
Low power modes
- 33 μA/MHz in Active Mode (EM0) at 39.0 MHz
- 2.8 μA EM2 DeepSleep current (256 kB RAM retention and RTC running from LFXO)
- 1.3 μA EM2 DeepSleep current (16 kB RAM retention and RTC running from LFRCO)
Packages
- QFN68 8 mm x 8 mm x 0.85 mm
- QFN48 6 mm x 6 mm x 0.85 mm

Temperature Range – -40°C to +125°C

Silicon Labs will provide the EFR32FG28 Pro Kit for sub-GHz and 2.4 GHz IoT device development with either +14 dBm or +20 dBm Tx output power for the 868-915 MHz bands. We don’t have information about the availability of the evaluation kit, but the company says the FG28 is currently sampling and general availability is planned before the end of Q3 2023. Silicon Labs also plans to launch FG28 derivatives specifically optimized for Amazon Sidewalk and Z-Wave Long-Range. More details may be found on the product page and press release.

Jean-Luc Aufranc (CNXSoft)

Jean-Luc started CNX Software in 2010 as a part-time endeavor, before quitting his job as a software engineering manager, and starting to write daily news, and reviews full time later in 2011.