STMicroelectronics STEVAL-IHT001V1

Overview

STEVAL-IHT001V1 from STMicroelectronics is a thermostat control demonstration board for refrigerator systems, built around the ST7Lite39 8-bit microcontroller and implementing an active PFC boost converter with bipolar transistors (ACS102, ACS110, ACST6), delivering 36 W output from 220 Vac input in discontinuous-conduction mode.

For engineers reviewing the STEVAL-IHT001V1 datasheet, STEVAL-IHT001V1 pinout, STEVAL-IHT001V1 application, or STEVAL-IHT001V1 equivalent, this board serves as a validated reference design for cost-sensitive, RoHS-compliant refrigerator thermostat and defrost control with integrated NTC temperature sensing, door switch interface, buzzer feedback, and motor/light/defrost actuation.

Technical Context

The board implements a closed-loop analog PFC controller using discrete bipolar transistors-no dedicated PFC IC-where duty cycle modulation and output regulation are achieved via feedback from the boost inductor current and output voltage. The ST7Lite39 MCU handles system-level logic including temperature monitoring (via NTC on PA0–PA3), door state detection (J10), defrost timing (J3), and actuator control (J2 motor, J4 light, J11 NTC heater).

Signal conditioning includes RC-filtered analog inputs (C5/C9/C10/C11), ZVS detection circuitry (TP8), and discrete LED indicators (LED1–LED4) tied to PB0–PB3. The design operates at fixed frequency with variable on-time, leveraging the ST7Lite39's HS (high-speed) I/O pins for real-time timing-critical functions like zero-voltage switching coordination and buzzer tone generation.

Key Specifications

Availability

STEVAL-IHT001V1 is available at Aetrix Electronics and suitable for refrigerator thermostat development, HVAC control prototyping, and white-goods PFC reference design validation requiring stable component supply, legacy-ST ecosystem compatibility, and documented thermal management practices.

Supply support for STEVAL-IHT001V1 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 devices, sensors, and analog ICs for industrial, automotive, and consumer applications.

The STEVAL evaluation board series targets rapid prototyping of ST's embedded control and power solutions-this board specifically supports cost-optimized, discrete-PFC appliance control with legacy ST7 architecture.

FAQ

Is STEVAL-IHT001V1 still in production?

No-STMicroelectronics has marked STEVAL-IHT001V1 as obsolete (per Doc ID 18009 Rev 1, September 2010). It remains available through authorized distributors and Aetrix Electronics' legacy inventory for design continuity and repair support, but no new silicon or board revisions are planned.

Can the ST7Lite39 be replaced with a modern ST microcontroller?

Direct replacement is not drop-in: the ST7Lite39 uses proprietary ST7 core, DIP20 package, and specific peripheral mapping (e.g., HS I/O pins for ZVS timing). Migration requires firmware rewrite, PCB layout changes, and revalidation of PFC loop stability and thermal response.

What is the role of the ACS102 and ACS110 transistors?

ACS102 (Q3) and ACS110 (Q2) are bipolar junction transistors configured as the main switch and auxiliary switch in the boost PFC stage. They operate in DCM with base drive from ST7Lite39's PB6 and PB5, enabling zero-current turn-off and low conduction loss at 36 W output.

Does this board include safety isolation between mains and low-voltage sections?

No reinforced or basic isolation is implemented: the board uses direct mains coupling (TP1/TP3) with shared ground plane. It is intended for lab evaluation only-not for end-product use without additional isolation, enclosure, and certification per IEC 60335-1 and IEC 61000-4-x standards.