As 4K ultra-HD displays and multi-brand device interconnectivity become increasingly prevalent, many existing reverse HDMI-to-DP products using conventional CS chip solutions suffer from compatibility issues and unstable signal performance. To address these challenges, we have developed a new conversion solution based on the Lontium LT6711A chip. This article provides an in-depth technical analysis—from system architecture and key specifications to engineering implementation and test results—presented in a style that resonates with engineering professionals.
1. Overview
Most reverse HDMI-to-DP products on the market adopt CS chip solutions, which frequently result in problems such as poor compatibility, image jitter, ghosting, or color inaccuracies when interfacing with devices from various brands. To overcome these limitations, we have selected the Lontium LT6711A—a high-performance chip integrating an HDMI2.0 receiver, DP1.2/eDP1.4 transmitter, and USB Type C Alt Mode switching with PD control. This chip supports up to 4K×2K@60Hz output and includes several engineering optimizations that significantly enhance system compatibility and signal stability.
2. Technical Solution
2.1 System Architecture
HDMI Receiver
The LT6711A integrates an HDMI2.0 receiver with one clock lane and three data lanes, each capable of operating at up to 6 Gb/s, providing a total bandwidth of 18 Gb/s. It supports HDCP1.4/2.2 encryption, 8-bit color depth, and the Status and Control Data Channel (SCDC), ensuring full compliance with the HDMI2.0 standard.
DP Transmitter
For the display output, the chip adopts a four-lane transmission architecture in line with the VESA DP1.2 standard. It supports RBR (1.62 Gb/s), HBR (2.7 Gb/s), and HBR2 (5.4 Gb/s) link rates, enabling stable output of 4K×2K@60Hz. The built in optional SSC (Spread Spectrum Clocking with 0.5% down spreading) function reduces EMI, while internal Rterm calibration further ensures signal integrity.
USB Type C Integration
To support the latest USB Type C ecosystem, the LT6711A integrates CC logic and PD management units. It is compliant with USB Type C R1.2, DP Alt Mode V1.0, and USB PD R3.0—providing full-featured orientation and role detection and simplifying overall system design.
2.2 Engineering Board Design
In our engineering sample—“HDMI AM+Micro to DP F Model”—the LT6711A serves as the core signal conversion module:
- Board-Level Design:
The design utilizes a QFN64 package (7.5 mm × 7.5 mm), ensuring stable operation over a wide temperature range (–40°C to +85°C). The final product is housed in an anodized aluminum enclosure (45×11×21.5 mm) with a sandblasted finish, which enhances heat dissipation and anti-interference performance. - Interface Configuration:
An HDMI male connector interfaces with the signal source (e.g., a PC or media player), while a DP female connector delivers the signal to the display device. A Micro USB port provides the necessary power, ensuring a stable supply for mobile and portable applications.
3. Key Technical Specifications and Advantages
3.1 High-Definition Signal Transmission
- Resolution & Refresh Rate:
The solution reliably supports a resolution of 3840×2160 at a 60Hz refresh rate, delivering stable images without jitter, ghosting, or distortion—meeting the demands of high-end displays. - Color & Audio Support:
It supports 8 bit color depth and 8 channel audio transmission, ensuring synchronized and high quality video and audio outputs that adhere to industry standards.
3.2 Superior Compatibility and Signal Stability
- Multi Brand Device Adaptation:
Utilizing advanced HDMI reception and DP transmission techniques, the LT6711A accurately decodes and re encodes signals, ensuring precise clock synchronization and calibration. This results in significantly enhanced compatibility across different device brands. - Low EMI and Power Consumption:
The built in SSC function and optimized circuitry reduce EMI interference. Under 4K60Hz operating conditions, the chip’s power consumption is approximately 1W, making it ideal for energy efficient designs and mobile applications.
3.3 Integrated Design Benefits (Expanded)
One of the standout features of the LT6711A is its highly integrated design, which consolidates multiple essential functionalities into a single chip. This integration offers several key advantages:
Full-Featured USB Type C Support:
The LT6711A is engineered to support the complete range of USB Type C functionalities. It complies with USB Type C R1.2, DP Alt Mode V1.0, and USB PD R3.0 standards. By integrating CC logic and PD management within the chip, it eliminates the need for additional external controllers. This integration streamlines the design process and reduces BOM costs while ensuring that the system can automatically detect cable orientation and device roles (both DFP and UFP) with full accuracy. It also supports a three level current advertisement (USB default, 1.5A, and 3A@5V), which is critical for proper power negotiation in a variety of applications.
Simplified System Architecture:
With the integration of both the USB Type C alternate mode switch and power delivery control, the LT6711A significantly reduces the overall system complexity. There is no longer a need to incorporate separate chips for CC detection, power negotiation, and role swapping (FR_Swap). This not only minimizes the board space and reduces potential points of failure but also improves reliability and compliance with the latest USB Type C specifications.
Enhanced Power Management and Flexibility:
The chip’s PD management unit supports both Source and Sink roles, including DRP (Dual Role Port) functionality, and features advanced capabilities such as dead battery support. This means that even when no external power is applied, the chip can still maintain communication and proper operation—a feature particularly valuable for portable and battery-operated devices. In addition, the ability to support low-power standby mode further contributes to overall energy efficiency in integrated systems.
Seamless Mode Switching and Data Path Control:
Integrated SBU (Sideband Use) data path control for DP Alt Mode ensures that the chip can effectively manage the data lanes required for high-speed DP transmission. This facilitates a smooth transition between HDMI and DP modes, allowing the device to adapt quickly and reliably to different display configurations. The embedded design thus enhances signal integrity and maintains stable operation even under high data throughput conditions.
By embedding these critical functionalities into a single chip, the LT6711A not only reduces design complexity and BOM cost but also improves overall system performance. This integrated approach is a significant step forward compared to traditional CS chip solutions, which often require multiple discrete components that can introduce compatibility issues and reduce reliability.
3.4 Additional Engineering Benefits
- Wide Operating Range and Compact Package:
Fabricated using an advanced CMOS process and available in both BGA81 and QFN64 packages, the chip operates reliably between –40°C and +85°C, making it suitable for industrial, mobile, and consumer electronic applications.
4. Engineering Implementation and Test Validation
Our engineering sample testing validated the performance advantages of the LT6711A solution:
- Signal Testing:
Extensive tests conducted between the HDMI input and DP output at 4K×2K@60Hz consistently demonstrated stable image output with no significant color deviations or interference. Audio signals were clear and free of noise. - Compatibility Testing:
The solution was evaluated with various HDMI sources and DP display devices from different brands, achieving automatic recognition and efficient switching. This effectively addresses compatibility issues prevalent in traditional CS chip solutions. - Environmental Testing:
Long term stability tests conducted within the temperature range of –40°C to +85°C confirmed that both the chip and the board level design maintain excellent performance, rendering the solution suitable for industrial and high end consumer markets.
5. Conclusion
By implementing a reverse HDMI-to-DP 4K60Hz conversion solution based on the Lontium LT6711A chip, we have successfully overcome the compatibility and signal stability issues commonly associated with conventional CS chip designs. This solution not only delivers high definition, stable video signal conversion but also simplifies system design through integrated USB Type C functionality, thereby reducing BOM costs. Test results from our engineering sample clearly demonstrate the solution’s reliability and superiority in 4K applications.
This engineering approach offers a fresh perspective for addressing the challenges of high definition video interconnectivity, meeting current market demands while laying a robust foundation for future display applications.
