Project Description

The USB to Dual HDMI Converter is designed to connect two HDMI monitors to a PC over a single USB3.0 interface.
It serves as a USB Docking Station solution, enabling extended or mirrored displays for productivity, multimedia, and workstation applications.

This project was developed to meet the growing demand for multi-monitor setups in compact office environments, digital workstations, and mobile productivity solutions. The design focuses on delivering high-resolution display output while maintaining low CPU utilization and efficient power usage.

Working

The device is powered by the Silicon Motion SM768 USB Display Docking Station SoC, a high-performance USB graphics controller.

  • The SM768 supports multiple displays up to 4K Ultra HD resolution via USB.
  • Provides instant screen mirroring without driver installation.
  • Offers low CPU loading, low power consumption, and CAT compression technology for high image and video quality.

HDMI Outputs:

  • One direct HDMI output from SM768.
  • The second HDMI output is generated using an HDMI transmitter IC (ITI66121FN), which converts SM768 TTL data into HDMI signals.

Firmware and Connectivity:

  • A NAND Flash memory stores the SM768 firmware.
  • The device connects to the host PC via USB3.0 Micro-B interface.

Block Diagram

PCB Design

The PCB design features a 425-pin BGA SoC (SM768) on a 4-layer impedance-controlled board.

  • 100Ω impedance-controlled differential pairs for HDMI signals.
  • 90Ω impedance-controlled differential pairs for USB3.0 signals.

This ensures signal integrity, high-speed data transfer, and stable 4K performance.
Special attention was given to layer stackup, return path continuity, and high-frequency signal routing to meet HDMI and USB compliance standards.

Specifications

  • Video Outputs: Two HDMI 1.4
  • Supported Display Resolutions:
    • 4K (3840×2160) @ 30Hz
    • 2K & Full HD (1920×1080) @ 60Hz
  • Interface: USB3.0 Micro-B Connector
  • Software Compatibility:
    • Windows 7/8/10/11 (32-bit & 64-bit) + Server editions
    • macOS X
    • Linux (Ubuntu, RedHat, SUSE, etc.)
    • Android
  • Driver Requirement: No driver needed
  • Additional Feature: Custom startup logo support

Applications

  • Dual-monitor office productivity setups
  • Portable USB docking stations for laptops and ultrabooks
  • Digital signage systems with extended displays
  • High-resolution multimedia playback on multiple monitors
  • Engineering and design workstations requiring multi-screen output
  • Conference and presentation systems with dual HDMI output

Schematic

    / [pdf]

Photos


4-Layer PCB

Top Side

Bottom Side

Video Demo