Programmable RX Termination Unit Cells for Low-Parasitic Routing
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Solution Overview
Problem
Conventional programmable receiver (RX) termination in integrated circuit (IC) devices suffers from significant routing capacitance, leading to performance issues such as return loss and bandwidth loss at high frequencies due to unwanted parasitics.
Innovation Solution
A compact programmable termination circuit is designed using a unit cell configuration with multiple transistors and control signal buses, allowing for programmable termination modes to optimize resistance and common mode voltage, reducing routing and parasitics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional programmable RX termination is implemented with sufficient functionality, then complex termination modes are achieved, but routing capacitance and parasitics increase significantly
Solution Approach 1:
The termination circuit is divided into multiple independent unit cells, each capable of being programmed individually. This segmentation allows the circuit to achieve complex termination functionality through combinations of simple unit cells, rather than requiring a large monolithic structure that would increase routing capacitance.
Solution Approach 2:
Multiple unit cells are combined in parallel configurations to achieve the desired termination resistance and functionality. By merging identical simple unit cells rather than creating one complex unit, the design maintains simplicity at the unit level while achieving complexity at the system level through parallel composition.
2Adaptability or versatility
If conventional programmable RX termination uses sufficient die size for functionality, then complex termination functionality is achieved, but device area increases
Solution Approach 1:
The termination circuit is segmented into compact unit cells that can be efficiently packed on the die. Each unit cell has a minimized footprint, and the overall die size is controlled by the number of unit cells required, allowing scalable design that optimizes area usage.
Solution Approach 2:
Each unit cell is designed to be universal and multi-functional, capable of contributing to different termination modes when combined with other unit cells. This universality reduces the need for dedicated circuitry for each function, thereby minimizing the overall die size while maintaining complex termination capabilities.
3Adaptability or versatility
If conventional RX termination routing is designed for functionality, then termination modes are achieved, but parasitics affect high frequency performance
Solution Approach 1:
By segmenting the termination circuit into distributed unit cells, the routing length and associated parasitics are reduced compared to a centralized design. Each unit cell can be placed close to its associated input, minimizing the distance signals must travel and reducing accumulated parasitic effects at high frequencies.
4Object-affected harmful factors
If compact programmable termination is implemented, then routing and parasitics are reduced, but programmable functionality must be maintained
Solution Approach 1:
The compact unit cell structure provides a scalable framework where programmable functionality is achieved through the configuration and combination of segmented units rather than through complex internal circuitry within each unit. This maintains simplicity at the unit level while enabling complexity through system-level configuration.
Solution Approach 2:
The termination circuit employs dynamic programming capability where unit cells can be programmably enabled or disabled to achieve different termination modes. This dynamic configurability allows the compact structure to adapt to different functional requirements without requiring physically larger circuitry for each possible mode.
Data Source
AI summary
A unit cell for a programmable termination circuit in an integrated circuit and a method for programming such termination circuit are described. In an embodiment, such unit cells may have three n-type and three p-type transistors. A first transistor is coupled to receive a first float control signal. A second transistor is coupled to receive a second float control signal. The third and fourth transistors are coupled to receive a first termination voltage control signal. The fifth and sixth transistors are coupled to receive a second termination voltage control signal. The first float control signal and the second float control signal are a pair of complementary signals.