Product Introduction: ST85MM Programmable PLC Modem Chip
The ST85MM is a programmable power line communication (PLC) modem SoC for smart meter and grid communication applications. Integrating a programmable DSP with an Arm Cortex-M4 core, it supports multiple PLC protocols up to 500 kHz and is natively compatible with the Meters and More and ITU G.9904 (PRIME) standards. Housed in a 7 mm × 7 mm QFN56 package, the ST85MM boasts a highly integrated design and includes a complete PLC analog front-end, a dedicated encryption engine, and a PLC protocol stack emulation front-end. This facilitates end-to-end communication from the physical layer to the application layer in smart meters, smart gateways, and energy management terminals. The ST85MM's flexible programmability allows device manufacturers to deploy customized protocols, upgradeable algorithms, and security policies on the same chip, shortening product time-to-market and reducing bill of materials (BOM) costs. Combined with the ST85MM's low-power transceiver features and PRIME 1.4 Hybrid PLC+RF connectivity, devices can achieve highly reliable data transmission and remote management in mixed wired and wireless network environments.
ST85MM Product Description
The ST85MM's internal architecture combines a high-performance DSP with an Arm Cortex-M4 processor: the DSP is responsible for real-time signal processing, modulation and demodulation, and front-end filtering, while the Cortex-M4 is responsible for the protocol stack, device management, and upper-layer application logic. The ST85MM supports operating frequencies up to 500 kHz and complies with CENELEC EN50065, FCC, and ARIB regulations, ensuring compliance for cross-regional deployments. The chip integrates a dedicated cryptographic engine and hardware random number generator to ensure authentication and data confidentiality between the meter and gateway. The ST85MM's analog front end includes a programmable gain amplifier, narrowband filter, and low-noise receive chain, enhancing long-range weak signal reception. The 7 mm × 7 mm QFN56 package size makes the ST85MM easily integrated into various meter cores and small gateways, reducing the number of external components. The ST85MM's power management supports low-power wake-up and sleep strategies. When used with ultra-low-power wireless transceivers like the S2-LP, it enables simultaneous PLC and low-power wireless communication, meeting the energy requirements of long-term operation and meter reading in smart grid scenarios.
ST85MM Product Features
•Highly Integrated Computing and Communication Cores: The ST85MM utilizes a DSP + Arm Cortex-M4 dual-core architecture, balancing real-time signal processing and system-level control.
•Multi-Protocol and Wideband Support: Supports Meters and More, PRIME, and custom PLC protocols, with operating frequencies up to 500 kHz.
• Strict Compliance and Cross-Region Compatibility: The design meets EN50065, FCC, and ARIB standards, facilitating deployment in European, North American, and Asia-Pacific markets.
• Enhanced Security and Encryption: A built-in dedicated encryption engine and hardware random number generator support device authentication and data integrity verification.
• Optimized Low Power Consumption and Miniaturized Package: The ST85MM supports sleep/wakeup power strategies, and the 7mm×7mm QFN56 package facilitates compact device designs.
•PLC and RF Hybrid Connectivity: Compatible with the PRIME 1.4 Hybrid PLC+RF architecture, it can work with wireless modules such as the S2-LP to improve network redundancy and coverage.
ST85MM Application Case 1: Remote Meter Reading and Time-of-Use Billing for Residential Smart Meters
A power company upgraded its residential metering system, aiming to achieve minute-level electricity usage data collection, remote time-of-use billing, and abnormal electricity usage alerts. By adopting a meter core solution based on the ST85MM, smart meters achieve full PLC communication capabilities within a limited hardware budget. The ST85MM's DSP is responsible for local signal filtering and modulation and demodulation, ensuring stable transmission and reception in the complex and noisy environment of the city's power grid. The Cortex-M4 handles the protocol stack, meter data caching, and local event processing logic. Using the Meters and More protocol, natively supported by the ST85MM, the meter securely handshakes with the concentrator, uploads 15-minute granularity electricity usage data, and receives time-of-use tariffs from the operator. A built-in hardware encryption module ensures the confidentiality and tamper-proof nature of meter reading data during transmission. Leveraging the ST85MM's low-power mode, the meter can continue waking up and reporting data every cycle even when idle for long periods, minimizing overall power consumption and maintenance costs. After deployment, this project has achieved a remote meter reading automation rate exceeding 99%, significantly improving the accuracy of time-of-use billing, and reducing the response time for abnormal electricity usage detection from days to hours, significantly reducing operation and maintenance costs and the frequency of manual inspections. The ST85MM's small package also simplifies the replacement and upgrade of older meters, reducing the difficulty of on-site modifications and the duration of power outages.
ST85MM Application Case 2: Distribution Network Automation Gateway and Hybrid Communication Solution
An energy management solutions provider designed a gateway device for a distribution network microgrid project. The device required reliable communication with end devices over power lines while also being able to switch to low-power wireless backhaul when PLC coverage was insufficient. Using the ST85MM as the PLC processing core, the gateway implemented a PRIME 1.4 Hybrid PLC+RF hybrid communication strategy. The ST85MM handles PLC physical and link layer functions, and its programmable features adapt to different frequency bands and coding schemes. When PLC channel quality degrades or encounters sudden interference, the gateway automatically triggers redundant link switching with wireless modules such as the S2-LP, ensuring the immediate delivery of alarms and control commands. In this project, the ST85MM's hardware encryption module and device authentication mechanism are used to protect the security of distributed power and load control commands within the microgrid, preventing malicious manipulation. The gateway leverages the ST85MM's signal processing capabilities to implement real-time power quality monitoring (such as harmonic analysis and surge detection), locally storing the analysis results and periodically reporting them to a cloud platform for energy efficiency optimization. Field tests have shown that gateways using the ST85MM have increased communication success rates by over 15% in urban power distribution scenarios, reducing link recovery time to seconds. Furthermore, the hybrid communication strategy effectively reduces data loss, significantly improving the reliability and resilience of distribution network automation control.
