Silicon Labs BG22E, MG22E, FG22E wireless MCUs target energy harvesting, battery-free IoT devices

Silicon Labs xG22E is a family of wireless SoCs consisting of the BG22E, MG22E, and FG22E and designed to operate within an ultra-low power envelope required for battery-free, energy harvesting applications such as electronic shelf labels, Smart Home sensors, remote controls, and so on.

Like the just-announced Silicon Labs MG26, BG26, and PG26, the new xG22E family features a Cortex-M33 core clocked up to 76.8MHz. As an evolution of the low-power BG22, the BG22E offers Bluetooth 5.4 LE connectivity with “Energy Conservation” to further enhance battery longevity and even support designs that eliminate the need for batteries. The MG22E is similar but embeds an 802.15.4 radio for Zigbee connectivity, and the FG22E provides a 2.4GHz proprietary plus the Cortex-M33 is clocked up to 38.4MHz.

BG22E MG22E FG22E energy harvesting wireless microcontroller
Block diagram for BG22E and MG22E. FG22E is similar but only supports 2.4 GHz proprietary

Silicon Labs BG22E, MG22E, FG22E specifications:

  • MCU – Arm Cortex-M33 @ 76.8 MHz with DSP and FPU (38.4 MHz for FG22E)
  • Memory – Up to 32 kB RAM data memory
  • Storage – Up to 512 kB flash program memory
  • Wireless
    • 2.4 GHz radio operation
    • Protocol Support
      • BG22E
        • Bluetooth 5.4 Low Energy
        • Direction finding using Angle-of-Arrival (AoA) and Angle-of-Departure (AoD)
        • Bluetooth Mesh
        • 2.4 GHz Proprietary
      • MG22E
        • Bluetooth 5.2 Low Energy
        • Direction finding using Angle-of-Arrival (AoA) and Angle-of-Departure (AoD)
        • Bluetooth Mesh Low Power Node (512 kB parts only)
        • Zigbee PRO/Green Power
        • 2.4 GHz Proprietary
      • FG22E – 2.4 GHz Proprietary
    • Radio Performance
      • Sensitivity
        • -106.7 dBm @ 125 kbps GFSK
        • -102.3 dBm sensitivity @ 250 kbps GFSK (MG22E only)
        • -102.3 dBm sensitivity @ 250 kbps O-QPSK DSSS (FG22E only)
        • -98.9 dBm @ 1 Mbit/s GFSK
        • -96.2 dBm @ 2 Mbit/s GFSK
      • TX power up to 6 dBm
      • Current – 2.5 mA Rx; 3.4 mA Tx @ 0 dBm; 7.5 mA Tx @ 6 dBm
  • Peripherals
    • 12-bit 1 Msps SAR ADC
    • Up to 26x GPIO pins with output state retention and asynchronous interrupts
    • 8-channel DMA Controller
    • 12-channel Peripheral Reflex System (PRS)
    • 4x 16-bit Timer/Counter with 3 Compare/Capture/PWM channels
    • 1x 32-bit Timer/Counter with 3 Compare/Capture/PWM channels
    • 32-bit Real Time Counter
    • 24-bit Low Energy Timer for waveform generation
    • 1x Watchdog Timer
    • 2x USART (UART/SPI/SmartCard (ISO 7816)/IrDA/I2S)
    • 1x Enhanced UART (EUART)
    • 2x I2C interface with SMBus support
    • Digital microphone interface (PDM)
    • Precision Low-Frequency RC Oscillator enabling single-crystal operation
    • RFSENSE with selective OOK mode
    • Die temperature sensor with +/-2 degree C accuracy
  • Security
    • Secure Boot with Root of Trust and Secure Loader (RTSL) (Part of xG22 family, but not xG22E)
    • Hardware Cryptographic Acceleration for AES128/256, SHA-1, SHA-2 (up to 256-bit), ECC (up to 256-bit), ECDSA, and ECDH
    • True Random Number Generator (TRNG) compliant with NIST SP800-90 and AIS-31
    • ARM TrustZone
    • Secure Debug with lock/unlock (Part of xG22 family, but not xG22E)
  • Supply Voltage – 1.71 V to 3.8 V single power supply
  • Power Consumption
    • 3.6 mA Rx current (1 Mbps GFSK)
    • 3.9 mA RX current (250 kbps O-QPSK DSSS) – MG22E and FF22E
    • 4.1 mA Tx current @ 0 dBm
    • 8.2 mA Tx current @ 6 dBm
    • 27 μA/MHz in Active Mode (EM0) at 76.8 MHz
    • 26 μA/MHz in Active Mode (EM0) at 38.4 MHz
    • 1.40 μA EM2 DeepSleep current (32 kB RAM retention and RTC running from LFXO)
    • 1.75 μA EM2 DeepSleep current (32 kB RAM retention and RTC running from Precision LFRCO)
    • 1.05 μA EM3 DeepSleep current (8 kB RAM retention and RTC running from ULFRCO)
    • 0.17 μA EM4 current
  • Temperature Range – -40 °C to 125 °C
  • Packages
    • QFN40 – 5 x 5 x 0.85 mm
    • QFN32 – 4 x 4 x 0.85 mm
    • TQFN32 – 4 x 4 x 0.30 mm
SiLabs xG22E Explorer Kit
SiLabs xG22E Explorer Kit

BG22E, MG22E, and FG22E look identical to the BG22, MG22, and FG22 apart from removed security features and the “Ambient Power” feature that’s not clearly documented at the time of writing. Highlights for the new “E” parts include:

  • Ultra-fast, low-energy cold start for applications starting from a zero-energy state to transmit packets and then rapidly return to sleep. An xG22E device wakes up in only eight milliseconds and uses only 150 micro-joules, or roughly 0.003% of the energy needed to power a 60-watt equivalent LED lightbulb for one second.
  • Energy-conserving deep sleep swift wake-up reduces wake-up energy by 78% compared to other (unnamed) Silicon Labs devices.
  • Power-efficient energy mode transition to transition in and out of energy modes by mitigating current spikes or inrush, which can harm energy storage capacity.
  • Multiple deep sleep wake-up options, such as RFSense, GPIO, and RTC wake-up sources from the deepest EM4 sleep mode, are ideal for extended storage.

Silicon Labs xG22E wireless microcontrollers work with e-peas Power Managed Integrated Circuits (PMICs) designed for energy harvesting which we’ve previously seen in the Conexio Stratus board (solar energy harvesting) and WattUp 1W active energy harvesting developer kit.

The companies co-developed two energy harvesting shields for Silicon Labs’ energy-optimized xG22E Explorer Kit. One of the shields relies on the AEM13920 dual-harvester, which allows it to pull energy simultaneously from two distinct energy sources such as indoor or outdoor light, thermal gradients, and electromagnetic waves. The second shield is based on e-peas’ AEM00300 shield to harvest power from random pulsed energy sources. Both are designed to slot onto the Explorer Kit pictured above.

The press release does not mention when the xG22 family will become available, but we can get this information in the related blog post with Silicon Labs anticipating that xG22E will become generally available in June. More details may be found on the product pages, and the company will host an unboxing Tech Talk on May 9 showcasing the new xG22E Explorer Kit.

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