STMicroelectronics ST7570

Overview

ST7570 from STMicroelectronics is a fully integrated narrow-band power line networking system-on-chip implementing IEC61334-5-1 S-FSK PHY/MAC, featuring embedded 56 MHz PHY processor and 28 MHz protocol controller cores, programmable bit rate up to 2.4 Kbps at 50 Hz, 1 Hz-step carrier tuning up to 148.5 kHz, and integrated 1 A_rms single-ended power amplifier for mains coupling in smart metering systems.

For engineers reviewing the ST7570 datasheet, ST7570 pinout, ST7570 application, or ST7570 equivalent, key selection considerations include zero-crossing synchronization capability, embedded thermal shutdown thresholds (T_TH4 = 153–187 °C), PGA gain range (−18 dB to +30 dB), TX_GAIN 32-step logarithmic attenuation, and compliance with EN50065/FCC Part 15 conducted emission limits.

Technical Context

The ST7570 employs dual-core architecture: a 56 MHz PHY processor handling S-FSK modulation/demodulation with SNR estimation and RSSI, and a 28 MHz protocol controller executing IEC61334-5-1 MAC layer, alarm management, repeater call, and intelligent search initiator. Its analog front end integrates ADC/DAC, PGA with automatic gain control, and a high-linearity transmission path with configurable active filtering topology.

Zero-crossing synchronization uses either analog ZC_IN_A (±10 V_p-p, ±30 mV hysteresis) or digital ZC_IN_D input, feeding a dedicated PLL for precise timing alignment. The power amplifier supports up to 14 V_p-p output into 50 Ω with THD < 0.15%, HD2 ≤ −63 dBc, and HD3 ≤ −63 dBc - critical for regulatory-compliant mains signaling.

Key Specifications

Pinout & Package

VFQFPN48 package with exposed thermal pad; 7 mm × 7 mm footprint, 0.5 mm pitch, suitable for high-density industrial PCB layouts requiring thermal dissipation.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar S-FSK power line communication applications.

Compared with MAX2990 and TI PLC100, the ST7570 delivers turnkey IEC61334-5-1 compliance with zero software porting effort, integrated thermal/current protection for unattended operation, and VFQFPN48 packaging optimized for thermal management in enclosed meter enclosures.

Availability

ST7570 is available at Aetrix Electronics and suitable for smart metering, street lighting control, and command & control networking requiring stable component supply across extended product lifecycles and industrial temperature ranges.

Supply support for ST7570 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, and power management solutions for industrial, automotive, and smart infrastructure markets.

The ST7570 belongs to ST's Power Line Communication (PLC) SoC product line, engineered specifically to replace discrete modem designs in utility-grade metering and grid automation with single-chip, standards-compliant, thermally robust solutions.

FAQ

What is the maximum permissible mains voltage that can be coupled through the ST7570's PA_OUT pin?

The ST7570's PA_OUT pin is rated for continuous 14 V_p-p output into 50 Ω, with absolute maximum non-repetitive peak current of 5 A and rms current of 1.4 A. When interfaced with standard capacitive coupling networks (e.g., 100 nF + 10 Ω series), it safely handles 230 V_RMS AC mains with isolation barriers compliant with IEC61000-4-5 surge immunity requirements. External filtering must ensure conducted emissions meet EN50065 Class A limits.

How does the ST7570 handle zero-crossing synchronization in regions with distorted or noisy AC waveforms?

The ST7570 provides dual zero-crossing inputs: ZC_IN_A accepts bipolar analog signals (±10 V_p-p) processed by an internal Schmitt trigger with 62–78 mV hysteresis, rejecting noise spikes below threshold; ZC_IN_D accepts clean digital edges. The embedded PLL dynamically tracks zero-crossing period variations up to ±5% and compensates for phase delay, ensuring stable time-slot alignment even under harmonic-rich or sag/swell conditions.

Can the ST7570 operate without an external crystal oscillator?

Yes - the ST7570 supports both external 8 MHz crystal (XIN/XOUT) and external clock injection (8 MHz square wave on XIN only, with XOUT left floating). Internal PLLs generate all required clocks: 8 MHz for AFE, 28 MHz for protocol controller, and 56 MHz for PHY processor. Crystal ESR must be ≤100 Ω and load capacitance 16–20 pF; clock jitter tolerance is ±150 ppm, matching typical ceramic resonator stability.

What design provisions does the ST7570 offer for meeting FCC Part 15 Subpart B conducted emission limits?

The ST7570 integrates a high-linearity 1 A_rms power amplifier with HD2/HD3 ≤ −63 dBc and THD < 0.15%, plus accessible PA_IN+/PA_IN− pins enabling user-designed active filters to suppress harmonics. Combined with programmable TX_GAIN attenuation and configurable carrier placement (1–148.5 kHz), it allows precise spectral shaping. Reference designs use 2nd-order LC filters with Q < 3 to meet FCC 15.109 limits below 30 MHz without shielding or ferrites.