STMicroelectronics STEVAL-ISA021V1

Overview

STEVAL-ISA021V1 from STMicroelectronics is a single-output, off-line AC-DC reference design board based on the VIPer22A primary-switcher IC. It delivers 12 V / 0.84 A (10 W) from 90–264 VAC input, operates at fixed 60 kHz switching frequency, features optocoupler-based secondary-side regulation, and complies with EN55022 Class B EMI and Blue Angel standby power (<1 W) standards.

For engineers reviewing the STEVAL-ISA021V1 datasheet, STEVAL-ISA021V1 application, STEVAL-ISA021V1 schematic, or STEVAL-ISA021V1 alternative reference designs, this board serves as a validated starting point for low-power, cost-sensitive, single-sided SMPS implementations in industrial and consumer auxiliary power supplies.

Technical Context

The board implements a discontinuous conduction mode (DCM) flyback converter using the VIPer22A - an integrated 700 V MOSFET + current-mode PWM controller. Feedback is closed via TL431 shunt regulator and H11A817A/LTV817 optocoupler, enabling precise ±0.2% load regulation and 0% line regulation across full input range.

Thermal management relies on a wide two-ounce copper pad under the VIPer22A DIP package, limiting junction temperature to 123.7°C at 65°C ambient. Transformer T1 (Cramer CVP32-001) provides 1:0.127 primary-to-secondary turns ratio, 2.25 mH primary inductance, and 5500 VAC hipot isolation between windings.

Key Specifications

Availability

STEVAL-ISA021V1 is available at Aetrix Electronics and suitable for industrial control auxiliaries, smart meter power supplies, and IoT gateway standby converters requiring stable component supply, rapid prototyping validation, and regulatory-compliant reference implementation.

Supply support for STEVAL-ISA021V1 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, analog devices, and reference solutions for industrial, automotive, and consumer markets.

This board belongs to ST's STEVAL evaluation platform family, engineered to accelerate development of certified, production-ready AC-DC power supplies using ST's VIPer and HV converter product lines.

FAQ

What is the primary topology implemented on STEVAL-ISA021V1?

The board implements a discontinuous conduction mode (DCM) flyback converter using the VIPer22A primary-side switcher. Energy transfer occurs during the off-time of the internal MOSFET, with regulation enforced by optocoupler-coupled feedback to the VIPer22A's VDD pin via TL431.

Can output voltage be modified, and how?

Yes - output voltage is adjustable by changing R5 and R8 resistor values per Table 2 in AN1735. For example, replacing R5 (3.48 kΩ) and R8 (13.3 kΩ) enables configurations such as 5 V / 2 A or 24 V / 0.42 A, with corresponding transformer (T1) and capacitor (C9/C10) changes.

Does STEVAL-ISA021V1 include protection features?

Yes - it integrates output short-circuit protection and thermal shutdown via the VIPer22A's internal circuitry. The IC automatically disables switching under overtemperature or sustained overload, recovering autonomously once fault conditions clear.

Is the board RoHS compliant and suitable for production use?

Yes - all components meet RoHS Directive 2011/65/EU requirements. While intended as a reference design, its layout, BOM, and test data support direct adaptation into volume production, subject to final system-level safety and EMI validation.