STMicroelectronics ST75MM

Overview

ST75MM from STMicroelectronics is a METERS AND MORE®-compliant power line communication (PLC) system-on-chip integrating PHY and MAC layers for CENELEC A/B/C/D bands, supporting 132.5 kHz carrier frequency, UART-based host interface with TREQ handshake, and MIB-managed configuration for smart metering and grid automation applications.

For engineers reviewing the ST75MM datasheet, ST75MM pinout, ST75MM application, or ST75MM equivalent, key selection criteria include PLC protocol compliance (METERS AND MORE®), CENELEC band support, UART+TREQ host interface timing constraints, MIB object programmability (e.g., PHY index 2, MAC index 3), and thermal monitoring via SM frame bitfield (bits 6–7).

Technical Context

The ST75MM implements a complete narrowband PLC transceiver stack with integrated analog front-end, digital signal processor, and MAC layer logic optimized for EN 50065-1 compliant power-line networks. It supports configurable PHY parameters (MIB index 2), MAC behavior (MIB index 3), and custom frequency planning (MIB index 23).

Host communication uses a half-duplex UART (57600 baud, 8N1) plus dedicated TREQ synchronization signal to coordinate command arbitration; status messages (SM) report real-time modem state (TX/RX/PLC busy flags) and MIB reconfiguration status via 16-bit bitmask.

Key Specifications

Pinout & Package

ST75MM is housed in a 48-pin QFN package (7 mm × 7 mm, 0.5 mm pitch) with exposed thermal pad. Pin functions are defined per UM2241 Section 1.1 and Figure 1.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar PLC transceiver applications.

Compared with STLD1 and AR7400, the ST75MM uniquely balances standards-certified firmware, field-upgradable MIB configuration, and separation of PLC processing from host MCU-enabling modular design, long-term compliance maintenance, and thermal-aware operation in sealed meter enclosures.

Availability

ST75MM is available at Aetrix Electronics and suitable for smart metering, utility grid automation, and industrial PLC networking requiring stable component supply, long-lifecycle support, and METERS AND MORE® certification continuity.

Supply support for ST75MM includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

STMicroelectronics is a global semiconductor leader headquartered in Geneva, Switzerland, designing and manufacturing microcontrollers, analog ICs, MEMS, and power devices for industrial, automotive, and smart infrastructure markets.

The ST75MM belongs to ST's PLC Communication Solutions product line, engineered specifically for interoperable, standards-compliant smart grid endpoints-prioritizing protocol fidelity, regulatory certification readiness, and field-deployable robustness in harsh electrical environments.

FAQ

What host controller interface signals are mandatory for ST75MM operation?

The ST75MM requires three mandatory host interface signals: UART_TX/RX (shared half-duplex line), TREQ (push-pull output from host, low-active for command arbitration), and RESET_N (active-low hardware reset). No SPI or I²C interface is supported; UART must be configured at 57600 bps, 8N1, with no flow control.

How does the ST75MM indicate modem operational status to the host?

The ST75MM sends periodic Status Message (SM) frames starting with 0x3F, containing a 1-byte modem status field (reporting TX/RX/PLC busy/OVC/temperature) and a 2-byte MIB status bitmask (indicating which MIB objects-e.g., index 2 for PHY, index 3 for MAC-have been successfully reconfigured by the host).

Can the ST75MM operate outside the default 132.5 kHz carrier frequency?

Yes-the ST75MM supports custom carrier frequencies via MIB index 23 (PHY custom frequencies), allowing configuration across CENELEC A/B/C/D bands. This requires writing validated frequency values into the MIB object; Table 15 in UM2241 defines valid register settings for each band.

What happens if the host fails to acknowledge an ST75MM frame within TACK time?

If the ST75MM does not receive ACK (0x06) or NAK (0x15) within the TACK timeout (managed by MIB object index 13), it discards the frame and takes no further action. The host must then reinitiate the transaction using 0x03 as the frame start byte to signal repetition and avoid duplicate processing.