STMicroelectronics STLUX325ATR

Overview

STLUX325ATR from STMicroelectronics is a digital lighting and power conversion controller integrating an STM8 microcontroller core and six autonomous SMED (State Machine Event Driven) PWM generators. It delivers 1.3 ns PWM resolution, hardware DALI 2.0 compliance (IEC 62386), and 4 analog comparators with <50 ns propagation delay-enabling precise zero-current detection in resonant LLC ballasts for high-efficiency LED drivers.

For engineers reviewing the STLUX325ATR datasheet, STLUX325ATR pinout, STLUX325ATR application, or STLUX325ATR equivalent, key selection considerations include SMED coupling modes, DALI bus timing tolerance (1.2/2.4/4.8 kHz), ADC sequencer channel count (6 inputs), comparator reference configuration (4 internal + 1 external), and VFQFPN32 package thermal performance at 105 °C ambient.

Technical Context

The STLUX325ATR implements a dual-layer control architecture: six independent SMED units operate autonomously at up to 96 MHz PLL-derived timing, reacting to events (DIGIN, comparator outputs, PWM feedback) with 10.4 ns latency; each SMED supports IDLE/S0–S3/HOLD states and configurable dithering for 1.3 ns effective PWM resolution. The integrated STM8 core (16 MHz max CPU frequency) configures SMEDs, manages DALI frame encoding/decoding, and executes closed-loop algorithms without interrupting real-time PWM generation.

Its DALI peripheral includes dedicated hardware encoder/decoder, programmable noise rejection filter, and reverse-polarity tolerant transceiver-fully compliant with IEC 60929 and IEC 62386 including 24-bit extended frame support. The 10-bit ADC (with x1/x4 programmable gain op-amp) samples up to 6 channels via hardware sequencer, while four comparators provide sub-50 ns response for fast overcurrent protection in synchronous rectification topologies.

Key Specifications

Pinout & Package

VFQFPN32 (5 × 5 mm, 0.5 mm pitch) package with exposed thermal pad; optimized for thermal dissipation in compact LED driver PCB layouts.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar digital lighting and power conversion controller applications.

Compared with STLUX385A, STLUX325ATR reduces pin count and package size while retaining identical SMED architecture, DALI compliance, and memory specs-making it optimal for space-constrained LED drivers. Versus UCC28911, it trades fixed-function simplicity for full programmability, enabling topology reuse across PFC, LLC, and HID applications with one firmware base.

Availability

STLUX325ATR is available at Aetrix Electronics and suitable for LED driver development, digital ballast manufacturing, and industrial SMPS design requiring stable component supply, long-term lifecycle assurance, and automotive-grade thermal robustness.

Supply support for STLUX325ATR 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 consumer markets.

The STLUX family targets digital lighting and power conversion systems-specifically engineered to replace analog PWM controllers and discrete microcontroller + peripheral combinations with a single-chip solution featuring hardware-accelerated SMED timing and DALI 2.0 compliance.

FAQ

What is the maximum achievable PWM frequency using SMED dithering on STLUX325ATR?

The SMED subsystem operates with a native 96 MHz clock derived from the internal PLL. With dithering enabled, the effective PWM resolution reaches 1.3 ns, allowing theoretical frequencies up to 769 MHz-but practical limits are imposed by external gate driver rise/fall times and layout parasitics. In production LED drivers, users achieve stable 1–2 MHz switching with <1% duty cycle jitter using SMED0–SMED4 outputs.

Does STLUX325ATR support DALI master functionality or only slave mode?

STLUX325ATR implements only DALI slave functionality per IEC 62386-102, with hardware encoder/decoder for receiving commands and transmitting status. It does not include master arbitration logic or multi-drop bus management. For master-side control, a separate microcontroller or dedicated DALI master IC (e.g., TI DLPC350) must be used in conjunction with STLUX325ATR as the endpoint driver.

How is the 1.3 ns PWM resolution achieved given the 16 MHz STM8 core clock?

The 1.3 ns resolution is generated entirely by the SMED hardware subsystem, which runs independently of the STM8 core using its own 96 MHz PLL clock domain. The STM8 configures SMED registers during initialization but does not participate in real-time PWM edge generation-eliminating software interrupt latency and enabling sub-nanosecond timing precision unattainable by timer-based MCU PWM.

Can the 4 analog comparators be used simultaneously with the 6-channel ADC without performance degradation?

Yes-the comparators and ADC operate on independent clock domains and analog front-ends. Comparators use dedicated high-speed comparators with internal 4-bit references, while the ADC employs a separate 10-bit SAR converter with programmable gain amplifier. Both can run concurrently; for example, comparators detect overcurrent faults while ADC monitors PFC output voltage and temperature sensor readings in the same switching cycle.