HDMI Termination Circuit for High-Speed Signal Reflection Control
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Solution Overview
Problem
HDMI transmitter systems face signal integrity degradation due to increased signal reflection as data transmission speed increases, particularly with longer cables and unknown devices, overwhelming built-in error correction and resulting in communication errors such as no picture, jumping images, or snowy displays.
Innovation Solution
A termination circuit is introduced that conditionally provides a termination resistance between the positive and negative transmission pins, utilizing a bias unit to select the higher voltage and a termination resistor unit formed on a well region biased by this voltage, with a control unit generating a termination resistor control signal to manage the resistance dynamically.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If data transmission speed is increased, then productivity is improved, but signal integrity is degraded due to increased signal reflection
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the termination resistance value based on the data transmission speed. When transmission speed exceeds a threshold (e.g., 1.65 Gbps), the termination resistance is activated or adjusted to match the cable impedance, thereby reducing signal reflection and maintaining signal integrity at high speeds.
Solution Approach 2:
The invention implements dynamics by making the termination resistance controllable and adjustable rather than fixed. A control unit dynamically enables or disables the termination resistance based on detected transmission conditions, allowing the system to adapt to varying data rates and cable lengths, thus resolving the contradiction between high-speed transmission and signal integrity.
2Ease of operation
If cable length is increased, then ease of operation is improved, but signal reflection increases causing communication errors
Solution Approach 1:
The patent uses parameter changes by adjusting the termination resistance value according to cable length. For longer cables, the termination resistance is activated to match the cable impedance, compensating for signal degradation and reflection issues that occur with increased cable length, thereby maintaining reliable communication.
Solution Approach 2:
The system employs feedback mechanisms to detect transmission conditions (such as cable length and signal quality) and automatically adjusts the termination resistance accordingly. This closed-loop control ensures that the termination impedance matches the cable characteristics, reducing reflections and communication errors regardless of cable length.
3Reliability
If termination resistance is always provided, then signal integrity is improved, but device complexity increases
Solution Approach 1:
The patent applies dynamics by implementing a controllable termination resistance that can be dynamically enabled or disabled based on transmission conditions. Rather than always providing termination resistance, the system activates it only when needed (e.g., at high data rates or with long cables), reducing unnecessary circuit complexity while maintaining signal integrity when required.
Solution Approach 2:
The invention uses parameter changes by making the termination resistance value adjustable based on operating conditions. The control unit modifies the termination resistance parameter according to data transmission speed and cable characteristics, providing optimal signal integrity only when necessary, thus avoiding the complexity of always-active termination circuits.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution effectively reduces signal reflection, enhances signal integrity, and allows for the use of longer and less expensive HDMI cables by dynamically adjusting the termination resistance in response to data transmission speed, thereby improving the reliability of HDMI connections.
Implementation Method 1
The bias unit generates a bias voltage by selecting the higher voltage among a first voltage received through the positive transmission pin and a second voltage received through the negative transmission pin
Implementation Method 2
The termination resistor unit is formed on a well region biased by the bias voltage, and conditionally provides a termination resistor (e.g., a fixed or variable predetermined termination resistance) between the positive transmission pin and the negative transmission pin in response to a termination resistor control signal
Data Source
AI summary
A termination circuit for a HDMI transmitter includes a bias unit and a termination resistor unit connected in parallel between a positive transmission pin and a negative transmission pin. The bias unit generates a bias voltage by selecting the higher voltage among a first voltage received through the positive transmission pin and a second voltage received through the negative transmission pin. The termination resistor unit is formed on a well region biased by the bias voltage, and conditionally provides a termination resistance between the positive transmission pin and the negative transmission pin in response to a termination resistor control signal. The termination circuit conditionally provides a termination resistance without a leakage current. The termination resistance may be varied by using an n-bit control code.