EFR32BG22 vs STM32WB55

EFR32BG22 vs STM32WB55: Silicon Labs vs ST BLE SoC Comparison

Overview

The EFR32BG22 from Silicon Labs and the STM32WB55 from STMicroelectronics represent two mature, well-documented BLE SoC families with meaningfully different architectures. The EFR32BG22 uses a single ARM Cortex-M33 core with a tightly integrated radio subsystem, while the STM32WB55 employs a dual-core design pairing an application-side Cortex-M4F with a dedicated radio-side Cortex-M0+ — a fundamental architectural difference with consequences for real-time behavior, firmware complexity, and ecosystem tooling.

The EFR32BG22 prioritizes ultra-low power and compact footprint. It supports BLE 5.2, offers Silicon Labs' Secure Vault Mid security, and is available in a 4×4 mm package — making it attractive for wearables, medical patches, and disposable IoT nodes where die area and current draw are the defining constraints. Its 352 KB Flash is sufficient for straightforward BLE peripheral firmware but limits dual-bank OTA flexibility.

The STM32WB55 is a mid-range multiprotocol SoC built for developers already comfortable in the STM32 ecosystem. With 1 MB of application Flash, 256 KB of RAM, the rich STM32 HAL/LL driver library, and Cube IDE integration, it dramatically lowers the barrier to entry for engineers coming from STM32 microcontroller backgrounds. The dual-core architecture allows the M4F application core to run FreeRTOS, USB, or complex peripheral tasks while the M0+ handles BLE stack operations independently, providing deterministic radio timing without interrupt latency concerns from the application processor.

Key Differences

• Core architecture: EFR32BG22 uses a single M33; STM32WB55 uses a dual-core M4F (application) + M0+ (radio), offering better real-time radio isolation.
• Memory: BG22 has 352 KB Flash / 32 KB RAM; STM32WB55 has 1 MB Flash / 256 KB RAM split between cores, enabling larger applications and comfortable dual-bank OTA.
• Ecosystem: STM32WB55 inherits the full STM32 middleware stack — FreeRTOS, USB, FATFS, TouchGFX integration; BG22 relies on Silicon Labs' Simplicity SDK and Gecko OS.
• Protocols: STM32WB55 supports BLE 5.0/5.2 and Zigbee/OpenThread concurrently; BG22 is BLE-only.
• Power: BG22 achieves approximately 1.0 µA in deep sleep (EM2); STM32WB55 reaches around 2.4 µA in Stop2 mode — both are competitive but BG22 has an edge in lowest-power scenarios.
• USB: STM32WB55 includes a full-speed USB 2.0 FS interface; BG22 does not — this is decisive for applications requiring USB HID or CDC.
• Security: Both offer hardware AES-128/256; BG22 adds Secure Vault Mid (key wrapping, attestation); WB55 includes a hardware PKI and a 128-bit UID.

Use Cases

EFR32BG22 is ideal for: - Compact, coin-cell-powered BLE sensors with aggressive power budgets - Medical wearables and disposable patches requiring BLE 5.2 long-range PHY - High-volume consumer tags where minimizing package size and BOM cost is critical

STM32WB55 is ideal for: - Products by teams with existing STM32 expertise seeking minimal retraining overhead - Designs requiring USB HID/CDC alongside BLE (HID-over-ATT">GATT bridges, dongle applications) - Smart home products needing concurrent BLE + Zigbee or Thread operation - Applications running FreeRTOS on the M4F with deterministic BLE timing on the M0+

Verdict

The EFR32BG22 wins on power consumption, package density, and pure BLE simplicity. The STM32WB55 wins on ecosystem breadth, dual-core real-time isolation, USB support, and multiprotocol capability. Teams already invested in the STM32 toolchain will find the WB55 far easier to bring up; teams prioritizing absolute battery life and small form factor will gravitate toward the BG22.