Compact Clock Distribution in IC Interface Blocks
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Solution Overview
Problem
High-density integrated circuits face challenges in clock distribution due to elongated physical structures, leading to increased jitter and circuit complexity, particularly in high-frequency applications like DDR SDRAM, where close synchronization between input/output clocks and core logic clocks is required.
Innovation Solution
The implementation of a compact clock tree with a butterfly configuration of I/O circuits, where each interface block has a logic hub with minimal length clock distribution that drives launch and capture logic, reducing physical length and circuit complexity, and enabling centralized distribution of higher frequency clocking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If I/O circuits are arranged in a linear array along the periphery of the IC, then the physical connectivity to external contacts is improved, but the clock distribution length increases leading to increased jitter and circuit complexity
Solution Approach 1:
The interface block is segmented into multiple sides (first side, second side, third side, fourth side) with I/O circuits distributed on different sides. This segmentation allows the clock distribution network to serve multiple I/O circuits from a centralized logic hub, reducing the overall clock tree length and complexity while maintaining peripheral connectivity to external contacts.
Solution Approach 2:
The patent transitions from a one-dimensional linear array of I/O circuits to a two-dimensional arrangement where I/O circuits are distributed on multiple sides of the interface block. This dimensional change enables a centralized logic hub to efficiently distribute clocks to I/O circuits on all sides, reducing clock distribution length and jitter while maintaining external connectivity.
2Area of stationary object
If the IC is designed with high density I/O circuits, then the footprint is reduced, but the clock distribution skew among data signals increases
Solution Approach 1:
Multiple I/O circuits distributed on different sides of the interface block are merged under a single centralized logic hub. This consolidation allows all I/O circuits to share a common clock distribution point, minimizing clock skew and improving synchronization precision while enabling high-density packing within a reduced footprint.
Solution Approach 2:
The logic hub provides localized clock distribution to I/O circuits on each side of the interface block, optimizing the clock tree structure for each local region. This local quality approach ensures minimal skew within each side while maintaining overall synchronization across the entire high-density interface block.
3Adaptability or versatility
If the clock distribution tree is extended to reach peripheral I/O circuits, then all I/O circuits can be clocked, but the clock jitter increases
Solution Approach 1:
The logic hub provides localized clock distribution to I/O circuits on each side of the interface block, optimizing the clock tree structure for each local region. This local quality approach ensures minimal skew within each side while maintaining overall synchronization across the entire high-density interface block.
Data Source
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AI summary
An integrated circuit includes core logic and a plurality of interface blocks disposed about a periphery of the core logic. A plurality of input or output (I/O) circuits is assigned to one of the plurality of interface blocks. The I/O circuits include external I/O circuits coupled to a device other than the integrated circuit and internal I/O circuits coupled to the integrated circuit. Each interface block includes a first plurality of I/O circuits disposed on a first side of the interface block and a second plurality of I/O circuits disposed on a second side of the interface block. Each interface block also includes interface logic for the interface block between the first plurality of I/O circuits and the second plurality of I/O circuits, and a logic hub that includes a clock distribution of minimal length that drives launch logic and capture logic to form the I/O circuits of the interface block.