TMDS Receiver Termination Circuit with Cascaded Transistors
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Solution Overview
Problem
Existing systems for transition-minimized differential signaling (TMDS) face challenges in managing termination paths for both NMOS and PMOS devices, particularly in the absence of a sink supply, requiring complex circuitry and failing to work effectively for supply-referred termination units.
Innovation Solution
The proposed solution involves an integrated circuit with a cascaded configuration of transistors and resistors along a termination path, using 1.8V MOSFETs and a 3.3V voltage supply, which includes calibration code control and a bulk generation circuit with peak detector circuitry to adjust output impedance and reduce leakage, suitable for HDMI systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a cascade topology is used to protect 1.8V devices from 3.3V supply, then device protection is improved, but the solution does not work for supply-referred termination using PMOS devices
Solution Approach 1:
The patent implements dynamic gate control for the PMOS device in the termination unit. The gate voltage is dynamically adjusted based on the supply state: when AVCC is present, the gate is driven to turn off the PMOS device to protect against overstress; when AVCC is absent, the gate control is adjusted to allow proper termination function. This dynamic adaptation resolves the contradiction between protection and compatibility.
2Reliability
If dynamic gate control is used to interface with 3.3V domain, then voltage tolerance is improved, but extra complex circuitry is required
Solution Approach 1:
The patent combines the gate control functionality with the existing termination unit structure. The dynamic gate control is integrated into the termination circuit rather than being a separate complex control system. The gate control logic is merged with the supply detection mechanism, allowing voltage tolerance improvement while minimizing additional circuitry complexity.
3Adaptability or versatility
If PMOS devices are used in termination unit for supply-referred termination, then termination functionality is improved, but gate voltages must be generated to turn off termination in absence of sink supply
Solution Approach 1:
The patent implements a self-service mechanism where the termination unit automatically manages its own gate voltage state based on the supply condition. The circuit detects the absence of AVCC supply and autonomously adjusts the gate voltage to turn off the PMOS device, eliminating the need for external gate voltage generation circuitry. This self-managing approach maintains functionality while reducing complexity.
Data Source
AI summary
The present disclosure relates to an apparatus for use in a transition-minimized differential signaling link (“TMDS”) receiver. The apparatus may include an integrated circuit electrically connected with a voltage supply. The integrated circuit may include a first transistor, a second transistor, and a resistor arranged in a cascaded configuration along a termination path. The first transistor may include calibration code control configured to adjust an output impedence.