Synaptics Serves Up Dual-Core SoC for Multiprotocol IoT Connectivity

When All About Circuits met with Synaptics at Electronica in November, it was clear that the company had its sights set on the Internet of Things (IoT) marketplace. Now, Synaptics is walking the talk with the recent release of its SYN20708 dual-core IoT system-on-chip (SoC). Let’s look at the details of Synaptics' new chip and how it may bolster the company's foray into IoT.

The SYN20708. Image used courtesy of Synaptics

A New Dual-Radio SoC

The Synaptics SYN20708 (datasheet linked) is a highly integrated, dual-radio SoC engineered for Bluetooth 5.4 and IEEE 802.15.4 protocols, including support for Zigbee, Thread, and Matter. To support this plethora of protocols, the architecture features two independent 2.4-GHz radios capable of simultaneous Bluetooth and IEEE 802.15.4 operations. 

These radios, which include integrated power and a low-noise amplifier, allow the system to support Bluetooth Classic and Bluetooth Low Energy with advanced features such as high-accuracy distance measurement (HADM), angle-of-arrival (AoA), and angle-of-departure (AoD) capabilities. The SoC also aligns with emerging Bluetooth 6.0 specifications, with IEEE 802.15.4 support, including OpenThread and ZBOSS stacks.

Veros SYN20708 block diagram. Image used courtesy of Synaptics

On the compute front, the SoC is supported by an Arm Cortex-M4 processor clocked at 160 MHz, along with a high-speed UART port for interfacing with an external host. The related memory configuration includes 1.64 MB of ROM, 544 KB of RAM, and 1.664 MB of code RAM, alongside 256 bytes of user-accessible OTP memory for calibration and system configuration.  

Fabricated using a 16-nm FinFET process, the SYN20708 achieves a normal receive mode power consumption of 2.48 mW from the 3.3-V rail and a normal-mode transmit power consumption of 135.83 mW at 14-dBm output power per core.  With a compact 5.5 mm × 5.5 mm package, secure boot functionality, and versatile antenna selection for advanced positioning, the SYN20708 targets industrial, consumer, and IoT applications.

Coexistence Interfaces and Timing for Multiprotocol IoT

The demand for multiprotocol solutions in IoT and industrial automation is driven by the growing complexity and density of connected devices. IoT ecosystems now routinely involve the simultaneous use of Bluetooth, Zigbee, Thread, and Matter, each serving distinct purposes. For example, Bluetooth Low Energy (BLE) excels in device-to-device communication with low latency, while IEEE 802.15.4-based protocols like Zigbee and Thread provide robust mesh networking for applications requiring high reliability.

One major technical challenge is managing coexistence in the crowded 2.4-GHz band, which is used by most IoT protocols alongside Wi-Fi. Without robust coexistence mechanisms, interference degrades performance, causing packet loss or increased latency. Advanced dual-radio systems, such as the SYN20708, address this by implementing hardware-level coexistence interfaces and precise timing control to mitigate interference.  

Many IoT protocols overlap in the frequency domain. Image used courtesy of Silicon Labs

Coexistence interfaces, such as Synaptics' Serial Enhanced Coexistence Interface (SECI), use real-time signaling between radios, allowing them to share information about upcoming transmissions. For example, a Bluetooth radio can signal a Zigbee radio when it needs priority access, avoiding overlapping transmissions. These interfaces often include priority levels and arbitration mechanisms enabling high-priority tasks, such as Bluetooth audio streaming, to preempt lower-priority operations like Zigbee network updates.

Precise timing control works in tandem by ensuring transmission and reception events are scheduled without overlap. In dual-radio systems like the SYN20708, this involves tight synchronization of the two 2.4-GHz radios. The system leverages low-latency processing to determine precise time slots for each protocol's activities. For instance, the hardware allocates microsecond-level time slices, preventing concurrent radioactivity that could cause interference. Additionally, timing protocols such as adaptive frequency hopping (AFH) in Bluetooth help avoid occupied channels by dynamically steering transmissions to clearer frequencies.

Bridging Multiprotocol Connectivity

As IoT ecosystems evolve, the capacity to manage multiple communication protocols simultaneously is becoming central to innovation. The SYN20708 reflects a trend toward more efficient integration of diverse protocols within compact, power-efficient designs. The SoC is currently available for purchase.