STMicroelectronics ST7538QTR

Overview

ST7538QTR from STMicroelectronics is a half-duplex FSK power line transceiver IC integrating a programmable line driver, dual linear regulators (5V/3.3V), UART/SPI host interface, and mains zero-crossing detection. It supports 8 carrier frequencies (60–132.5 kHz), up to 4800 BPS baud rate, 250 µVrms receiving sensitivity, and operates from a single 7.5–12.5 V supply. Used in CENELEC-compliant smart metering and home automation PLC networks.

For engineers reviewing the ST7538QTR datasheet, ST7538QTR pinout, ST7538QTR application, or ST7538QTR equivalent, key selection criteria include its integrated voltage/current-controlled PLI driver, dual-regulator power architecture, carrier/preamble detection logic, and register-programmable FSK modulation parameters for EN 50065-compliant deployment.

Technical Context

The ST7538QTR implements a fully integrated FSK modem with synchronous/asynchronous operation, PLL-based synchronization recovery, and digital filter-based demodulation. Its transmission path includes Automatic Level Control (ALC) with programmable gain steps (0.6–1.4 dB) and 30 dB dynamic range, while reception uses high-sensitivity analog front-end with selectable normal/high modes.

Control is executed via an internal 24- or 48-bit register accessed through UART or SPI; register bits configure carrier frequency (3-bit select), baud rate (2-bit), deviation mode (1-bit), header recognition length (8/16 bit), and auxiliary functions including watchdog timeout (1.5 s), band-in-use detection threshold (77–85 dB/µVrms), and zero-crossing synchronization delay (1 µs).

Key Specifications

Pinout & Package

TQFP44 Slug Down package with exposed thermal pad (pin 6 and 41 are substrate ground); 44-pin layout optimized for power line coupling, analog isolation, and digital interface separation.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar FSK power line transceiver applications.

Compared with ST7538QTR, ST7537QTR offers simpler register programming but limited frequency agility, while MAX2992ETM+ provides broader protocol support at the cost of reduced EN 50065 compliance out-of-box and no hardware zero-crossing trigger.

Availability

ST7538QTR is available at Aetrix Electronics and suitable for smart metering, home area networks, streetlight control, and industrial substation monitoring requiring stable component supply across extended product lifecycles.

Supply support for ST7538QTR 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, specializing in microcontrollers, power management, and analog/mixed-signal ICs for industrial, automotive, and consumer markets.

The ST7538QTR belongs to ST's dedicated power line communication transceiver product line, engineered specifically for EN 50065-compliant FSK-based smart grid infrastructure with emphasis on integration, noise resilience, and regulatory alignment.

FAQ

What is the maximum AC output voltage swing achievable on ATOP1/ATOP2?

The ST7538QTR delivers up to 6 Vpp differential AC output on ATOP1 and ATOP2 pins under specified conditions (PAVCC = 10 V, RLOAD = 50 Ω, carrier frequency = 132.5 kHz). This is achieved with active voltage control loop engagement and proper Vsense feedback configuration; output is programmable down to 3.5 Vpp via Vsense threshold adjustment.

Does the ST7538QTR support both UART and SPI interfaces simultaneously?

No - the interface type is selected at power-up via the UART/SPI pin (Pin 13): logic high configures UART mode, logic low selects SPI mode. The device does not support concurrent operation or runtime switching; the chosen interface governs all register access and data transfer operations throughout the session.

How is mains zero-crossing synchronization implemented in hardware?

Zero-crossing detection uses internal comparators monitoring ZCIN (Pin 16) against ±5 mV thresholds. When the AC waveform crosses zero, ZCOUT (Pin 15) asserts a clean digital pulse with 1 µs delay. This output can directly trigger transmission start or synchronize internal timers, enabling emission precisely at voltage minima to minimize electromagnetic interference.

What protection features are built into the integrated 5V and 3.3V regulators?

Both regulators include short-circuit protection and power-good (PG) monitoring: PG outputs (Pins 33 and 42) assert logic high only when respective outputs remain within tolerance (±5% for VDC, ±5% for DVdd) and exceed hysteresis thresholds (250 mV). Thermal shutdown and under-voltage lockout (UVLO at 3.7–4.1 V on PAVCC) further safeguard regulator operation.