STMicroelectronics EVAL6668-STB

Overview

EVAL6668-STB from STMicroelectronics is a reference design evaluation board implementing a 40W flyback switch-mode power supply based on the L6668 PWM current-mode controller, designed specifically for Set-Top Box (STB) and Personal Video Recorder (PVR) applications. It accepts universal AC input (90–265 V_rms), delivers four regulated DC outputs (1.8V/1.73A, 3.3V/0.5A, 5V/2.4A, 12V/1.9A avg), and achieves <1W standby consumption per EN60065 and global energy regulations.

For engineers reviewing the EVAL6668-STB datasheet, EVAL6668-STB pinout, EVAL6668-STB application, or EVAL6668-STB equivalent, this board serves as a validated hardware platform to evaluate L6668-based flyback topology performance-including cross-regulation under HDD spin-up load transients, burst-mode efficiency at light load, OVP response, and conducted EMI compliance pre-testing per EN55022 Class B.

Technical Context

This board implements a fixed-frequency (65 kHz) current-mode flyback converter operating in both continuous and discontinuous conduction modes. The L6668 controller integrates a high-voltage startup current source, programmable soft-start, slope compensation via S_COMP pin, and ST-BY pin-driven frequency reduction for light-load efficiency optimization.

Regulation uses optocoupled secondary-side feedback (TS2431 + SFH617A-4) referenced to the 12V/5V/3.3V rails, while 1.8V is transformer-coupled. Protection features include cycle-by-cycle overcurrent sensing (via R18/R19), auto-restart short-circuit protection on all outputs, and latch-off overvoltage protection triggered by DIS pin monitoring.

Key Specifications

Availability

EVAL6668-STB is available at Aetrix Electronics and suitable for Set-Top Box development, PVR power architecture validation, and flyback controller qualification requiring stable component supply, full documentation (AN2242), and production-ready layout guidance.

Supply support for EVAL6668-STB 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, specializing in power management, microcontrollers, analog ICs, and automotive-grade solutions.

EVAL6668-STB belongs to ST's power conversion reference design portfolio, developed to accelerate adoption of the L6668 controller in cost-sensitive, high-efficiency AC-DC applications for digital consumer electronics.

FAQ

What is the primary function of the EVAL6668-STB board?

The EVAL6668-STB is a fully assembled, tested reference design board demonstrating a 40W L6668-based flyback converter optimized for Set-Top Boxes and PVRs. It provides hardware validation of the controller's performance-including startup behavior, cross-regulation across four outputs, burst-mode efficiency, OVP latching, and thermal behavior under HDD spin-up loads-alongside complete schematics, BOM, and PCB layout files in AN2242.

Does EVAL6668-STB support multiple output regulation strategies?

Yes. It employs dual regulation methods: optocoupled secondary-side feedback (TS2431 + SFH617A-4) controls the 12V, 5V, and 3.3V outputs, while the 1.8V rail is regulated via transformer turns ratio coupling. This hybrid approach minimizes component count and improves transient response on critical digital rails without requiring additional post-regulators.

Can EVAL6668-STB be used for non-STB applications?

Yes-its 90–265 V_rms input, quad-output capability, and <1W standby make it applicable to other 40W-class consumer or industrial auxiliary supplies, such as network media adapters, IPTV gateways, or low-power industrial controllers. However, transformer and feedback component values are tuned for STB load profiles and may require re-optimization for significantly different load distributions or safety standards.

What documentation and support files ship with EVAL6668-STB?

EVAL6668-STB ships with the complete AN2242 Application Note (Rev 1.0), including electrical schematic (Figure 2), bill of materials (Table 7), transformer specifications (Section 9), PCB layout drawings (Figures 29–31), thermal images (Figures 27–28), and test waveforms. No separate user manual or software is included-the board is intended for hardware-level evaluation and design replication.