STMicroelectronics STEVAL-ISA129V1

Overview

STEVAL-ISA129V1 from STMicroelectronics is a demonstration board implementing a non-isolated flyback DC-DC converter delivering 16 V at up to 280 mA, based on the VIPer16 high-voltage off-line controller. It operates from universal AC input (90–265 VRMS), achieves ±5% output regulation, and supports <50 mW standby power when using auxiliary winding - targeting low-cost AC/DC adapter and auxiliary supply applications.

For engineers reviewing the STEVAL-ISA129V1 datasheet, STEVAL-ISA129V1 schematic, STEVAL-ISA129V1 application circuit, or STEVAL-ISA129V1 bill of materials, this page provides verified topology implementation details, thermal performance limits (60 °C max ambient), EMI-reduction features (115 kHz jittered PWM), and design trade-offs between auxiliary-winding-dependent vs. auxiliary-free supply modes.

Technical Context

The board implements a non-isolated flyback topology using the VIPer16 IC, which integrates an 800 V avalanche-rugged power MOSFET and current-mode PWM controller. Its 115 kHz switching frequency includes intentional jitter to reduce electromagnetic interference peaks, and it supports two supply configurations: auxiliary winding for ultra-low standby (<50 mW at 265 Vac) or internal current generator for transformerless operation.

Protection mechanisms include thermal shutdown with hysteresis and delayed overload protection. Output regulation precision is ±5% under low-frequency load and line conditions, while high-frequency ripple is specified at 50 mV peak-to-peak - reflecting inherent flyback transformer leakage and rectifier dynamics.

Key Specifications

Availability

STEVAL-ISA129V1 is available at Aetrix Electronics and suitable for industrial control auxiliary supplies, smart meter bias rails, low-power IoT gateway power stages, and white goods sub-power modules requiring stable component supply and reference design validation support.

Supply support for STEVAL-ISA129V1 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, designing and manufacturing microcontrollers, power ICs, sensors, and analog devices for industrial, automotive, and consumer markets.

This board belongs to ST's STEVAL evaluation platform series, engineered to accelerate prototyping of AC/DC conversion topologies using VIPer and other HV offline controllers - emphasizing cost-sensitive, safety-compliant, and EMI-optimized designs.

FAQ

Is STEVAL-ISA129V1 certified for safety standards such as UL or EN62368?

No. STEVAL-ISA129V1 is a demonstration board intended for lab evaluation only and lacks safety certification. It uses non-isolated topology, so user isolation barriers and external certification are required for end-product compliance. The board does not include reinforced insulation, creepage/clearance verification, or certified transformers.

Can STEVAL-ISA129V1 operate without an auxiliary winding?

Yes. The VIPer16 controller on this board supports auxiliary-free operation via its internal high-voltage current generator, eliminating the need for an auxiliary winding. This reduces transformer complexity and cost but increases no-load power consumption above 50 mW - a validated trade-off per ST's application note AN4171.

What is the purpose of frequency jittering in the VIPer16 used on this board?

Frequency jittering spreads the fundamental switching energy across a narrow band around 115 kHz, reducing peak EMI amplitudes by up to 10 dB. This allows simpler, lower-cost EMI filters and helps meet Class B conducted emissions limits without additional shielding or ferrite beads on the input line.

Does STEVAL-ISA129V1 support adjustable output voltage?

No. The output is fixed at 16 V by resistor divider and Zener-based feedback network. Output voltage adjustment would require redesigning the feedback loop components and validating loop stability - not supported out-of-box. ST provides alternative reference designs (e.g., STEVAL-ISA145V1) for adjustable outputs.