Unbalanced Clock Tree for Die-to-Die Interface Power Reduction
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Solution Overview
Problem
Conventional balanced clock trees in die-to-die interfaces require longer metal traces, increasing metal parasitic capacitance and dynamic power consumption, necessitating a more power-efficient solution for clock distribution.
Innovation Solution
Implementing unbalanced clock trees with varying metal route lengths for each bit, ensuring matching insertion delays between corresponding transmit and receive bits across dies, which reduces metal usage and power consumption while maintaining synchronized data transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a balanced clock tree is used to ensure uniform clock insertion delay to each bit, then synchronized data transmission is achieved, but metal usage and parasitic capacitance increase
Solution Approach 1:
The patent applies asymmetry by transitioning from a symmetric balanced clock tree to an asymmetric unbalanced clock tree configuration. The unbalanced clock tree uses varying metal trace lengths for different bits, eliminating the need for equal-length routing while maintaining synchronized transmission through pairing strategies. This asymmetric design reduces overall metal usage and parasitic capacitance while achieving the same functional goal of synchronized data transmission.
2Reliability
If a balanced clock tree is used to ensure uniform clock insertion delay, then synchronized data transmission is achieved, but parasitic capacitance increases
Solution Approach 1:
The unbalanced clock tree employs asymmetric routing where metal trace lengths vary by bit position, reducing total capacitance while maintaining synchronization through paired bit transmission. This asymmetric configuration minimizes the capacitive load on the clock distribution network compared to the symmetric balanced approach.
3Reliability
If a balanced clock tree is used to ensure uniform clock insertion delay, then synchronized data transmission is achieved, but dynamic power consumption increases
Solution Approach 1:
The unbalanced clock tree reduces dynamic power consumption by minimizing the total capacitive load through asymmetric routing. Since dynamic power is proportional to capacitance and switching frequency, the reduced capacitance in the unbalanced configuration directly lowers power consumption while maintaining synchronized transmission through the paired bit strategy.
4Use of energy by stationary object
If unbalanced clock trees are used to reduce metal usage and power consumption, then power efficiency is improved, but insertion delay matching between transmit and receive bits must be maintained
Solution Approach 1:
The patent uses copying by creating paired bit configurations where transmit and receive bits are matched in pairs. Each pair is designed to have matching insertion delays, allowing the unbalanced clock tree to reduce overall metal usage while maintaining precise delay matching for synchronized transmission through this pairing strategy.
Data Source
AI summary
Circuits for die-to-die clock distribution are provided. A system includes a transmit clock tree on a first die and a receive clock tree on a second die. The transmit clock tree and the receive clock tree are the same, or very nearly the same, so that the insertion delay for a given bit on the transmit clock tree is the same as an insertion delay for a bit corresponding to the given bit on the receive clock tree. While there may be clock skew from bit-to-bit within the same clock tree, corresponding bits on the different die experience the same clock insertion delays.