Multilevel Bus Driver Using Implicit Termination for Low Power
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Solution Overview
Problem
In high-speed chip-to-chip communication systems, existing technologies often result in unnecessary power consumption and system complexity due to the requirement for perfectly matched line terminations, which is not feasible in short propagation environments within integrated circuit devices.
Innovation Solution
A low power multilevel driver is developed that uses current sources and sinks with different output impedances to generate multiple signal levels on a single wire, optimizing power usage by eliminating the need for separate termination voltage sources and allowing for reduced line driver power consumption, even in environments where matched line terminations are not implemented.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If perfectly matched line terminations are implemented, then signal integrity is improved, but device complexity and power consumption increase
Solution Approach 1:
The patent extracts and eliminates the termination voltage source from the system by using current sources and sinks that directly generate the required signal levels without needing separate termination voltage sources. This reduces system complexity while maintaining signal integrity through the use of controlled current paths.
Solution Approach 2:
The current sources and sinks serve multiple functions: they generate signal levels, provide implicit termination, and enable multilevel signaling all in one component. This multi-functionality eliminates the need for separate termination circuits, reducing overall system complexity while maintaining reliable signal transmission.
2Reliability
If perfectly matched line terminations are implemented, then signal integrity is improved, but power consumption increases
Solution Approach 1:
The patent removes the separate termination voltage source that would consume power, replacing it with current sources and sinks that provide both signaling and implicit termination functions. This extraction of the termination function eliminates unnecessary power consumption while maintaining signal integrity.
Solution Approach 2:
The current sources and sinks provide self-service by simultaneously performing signaling and termination functions without requiring external termination voltage sources. The system serves itself by using the same components for multiple purposes, thereby reducing power consumption associated with separate termination circuits.
3Use of energy by moving object
If multilevel signaling is implemented without matched terminations, then power consumption is reduced, but signal integrity may deteriorate
Solution Approach 1:
The patent changes the fundamental parameters of the signaling system by using current sources and sinks with specific output impedances that are deliberately different from the transmission line characteristic impedance. This parameter change enables implicit termination that maintains signal integrity while allowing reduced power consumption operation without matched terminations.
Solution Approach 2:
The patent employs asymmetric output impedances for the current sources and sinks that are intentionally different from the transmission line characteristic impedance. This asymmetry creates an implicit termination effect that maintains signal integrity even without externally matched terminations, enabling low-power multilevel signaling.
4Measurement precision
If separate termination voltage sources are used, then signal levels are controlled, but device complexity increases
Solution Approach 1:
The current sources and sinks serve as universal components that both control signal levels and provide implicit termination without requiring separate termination voltage sources. This consolidation of functions into single components reduces device complexity while maintaining precise signal level control through the controlled current paths.
Solution Approach 2:
The patent merges the signal generation and termination functions into the same current source or sink components. By combining these functions, the system eliminates separate termination voltage sources, reducing device complexity while maintaining precise signal level control through the unified component design.
Data Source
AI summary
A driver for transmitting multi-level signals on a multi-wire bus is described that includes at least one current source connected to a transmission line, each current source selectively enabled to source current to the transmission line to drive a line voltage above a termination voltage of a termination voltage source connected to the transmission line via a termination impedance element, wherein each of the at least one current sources has an output impedance different than a characteristic impedance of the transmission line, and at least one current sink connected to the transmission line, each current sink selectively enabled to sink current from the transmission line to drive a line voltage below the termination voltage, each of the at least one current sinks having an output impedance different than the characteristic impedance of the transmission line.