STMicroelectronics STNRG328S

Overview

STNRG328S from STMicroelectronics is a digital controller IC for STC/HSTC open-loop resonant DC/DC converters, performing intermediate bus conversion from 40–60 V input to programmable output voltages via 2:1–10:1 conversion ratios, delivering 500 W–2 kW output power with peak efficiency of 98.4%, and featuring integrated SMED-based control, ZCD-driven deadtime/frequency management, and PMBus interface for real-time parameter programming in server power systems.

For engineers reviewing the STNRG328S datasheet, STNRG328S pinout, STNRG328S application, or STNRG328S equivalent, key selection criteria include resonant topology support (STC/HSTC), ZCD-enabled adaptive deadtime control, 140–300 kHz programmable switching frequency, 10-bit ADC with six analog inputs, and dual-voltage operation (3.3 V / 5 V).

Technical Context

The STNRG328S implements a State Machine Event Driven (SMED) architecture that autonomously generates six independent PWM signals and reacts to internal events (e.g., ZCD zero-current detection) and external triggers (e.g., ENABLE_STC, SelMasterSlave) without CPU intervention. Its core timing relies on an internal 96 MHz PLL for precise high-frequency PWM generation and ZCD matrix lookup.

Control execution is decoupled from firmware runtime: SMED handles real-time resonant timing (deadtime, frequency sweep), while the embedded STM8 supervisory MCU manages configuration, PMBus communication, EEPROM/Flash access, and protection state transitions - enabling deterministic response to overvoltage, undervoltage, overtemperature, and overcurrent faults.

Key Specifications

Pinout & Package

STNRG328S is housed in a VFQFPN32 (5 × 5 mm, 0.5 mm pitch) package with wettable flanks, optimized for high-density server PSU layouts and automated optical inspection (AOI).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar resonant DC/DC controller applications.

Compared with UCC28950 and LM5180-Q1, STNRG328S uniquely integrates ZCD-based resonant timing, hardware SMED execution, and full PMBus programmability - making it the only solution capable of achieving >98% efficiency at 2 kW in STC/HSTC topologies without external timing ICs or firmware development.

Availability

STNRG328S is available at Aetrix Electronics and suitable for server power supplies, telecom intermediate bus converters, AI accelerator card power delivery, and industrial 48 V DC microgrids requiring stable component supply, long-lifecycle support, and field-programmable resonant control.

Supply support for STNRG328S 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, power ICs, sensors, and analog devices for industrial, automotive, and communications markets.

The STNRG328S belongs to ST's digital power controller product line, engineered specifically for high-efficiency, high-power resonant DC/DC conversion in datacenter and telecom infrastructure where ZCD-driven adaptability and PMBus configurability are mandatory.

FAQ

What is the role of the SMED engine in STNRG328S?

The SMED (State Machine Event Driven) engine is a hardware-accelerated finite-state machine that autonomously executes resonant control tasks-including PWM generation, deadtime adjustment, frequency modulation, and protection triggering-without CPU intervention. It responds to ZCD events, digital inputs (e.g., ENABLE_STC), and comparator outputs within nanoseconds, ensuring deterministic timing critical for maintaining LC resonance across varying loads and temperatures.

How does STNRG328S support different STC/HSTC board configurations?

STNRG328S uses the SelCfgBoard pin (Pin 12) to read a resistor-divider voltage and select one of 15 preprogrammed STC/HSTC configurations stored in Flash memory. Each configuration defines conversion ratio, ZCD frequency range, capacitor type (X7R/U2J), and associated ZCD matrix parameters. This eliminates firmware reprogramming when swapping resonant tanks or adjusting output voltage in production.

Can STNRG328S operate with both 3.3 V and 5 V supply rails?

Yes, STNRG328S supports dual-supply operation: VDD (digital/I/O) and VDDA (analog) accept either 3.3 V or 5 V nominal input. Internal regulators condition these supplies to generate stable internal voltages, including a dedicated 1.8 V reference for ADC and comparators. This flexibility simplifies integration into legacy 5 V or modern 3.3 V server power domains without external level shifters.

What protections are implemented in hardware versus firmware?

Hardware protections include immediate response to VDRV_Prot (gate-drive undervoltage), VOUT_OVP/UVP, and overtemperature via dedicated comparators that directly assert EFUSE_Enable or disable PWM outputs - all independent of firmware. Firmware-managed protections (e.g., PMBus-configurable thresholds, cumulative fault counters, EEPROM-locked settings) provide configurable, persistent, and remotely adjustable safety layers but do not override hardware-fast shutdown paths.