Dual Clock-Data I/O Cell for Low-Delay Serial Interfaces
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Solution Overview
Problem
Conventional serial interface designs in integrated circuits suffer from propagation delays due to the physical and logical separation of data and clock paths, which are exacerbated by unnecessary components like level shifters and buffers, affecting the performance of time-critical operations such as read path communication in HDDs and data exchange with serial flash memory.
Innovation Solution
A dual-padded I/O cell integrates data and clock functionalities, eliminating unnecessary components and directly incorporating the flip-flop within the I/O cell's voltage domain, thereby reducing propagation delays and enhancing synchronization efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If separate standard I/O cells are used for clock and data signals, then broad compatibility between devices is achieved, but propagation delays increase due to unnecessary level shifters, buffers, and wire length
Solution Approach 1:
The patent combines the clock I/O cell and data I/O cell into a single integrated cell structure. The clock pad and data pad are both connected to the same I/O voltage domain, eliminating the need for separate level shifters and buffers. This merging reduces the number of components in the signal path and minimizes propagation delays while maintaining the ability to interface with external devices.
Solution Approach 2:
The integrated I/O cell performs multiple functions within a single structure: it handles both clock and data signals, provides level shifting for both signals, and offers buffering capabilities. This multi-functional design eliminates the need for separate dedicated cells for clock and data while maintaining compatibility with external devices.
2Ease of manufacture
If separate standard I/O cells are used for clock and data signals, then standardized interface design is maintained, but device complexity increases due to duplicated components and routing
Solution Approach 1:
The patent merges the clock I/O cell and data I/O cell into a single integrated structure, eliminating duplicated components such as level shifters and buffers. This reduces device complexity and the number of routing connections required while maintaining standardized interface capabilities through the unified I/O voltage domain.
3Ease of operation
If flip-flop is located in digital core voltage domain rather than I/O voltage domain, then data processing is simplified, but propagation delays increase due to separation of data and clock paths
Solution Approach 1:
The patent positions the flip-flop within the I/O voltage domain and integrates it with the clock input buffer in the same voltage domain. This eliminates the need for the clock signal to cross voltage domains to reach the flip-flop, reducing propagation delays. The flip-flop receives the clock signal directly from the clock input buffer without traversing through level shifters or buffers in the digital core, thereby minimizing the separation between data and clock paths.
Data Source
AI summary
A serial interface comprising an I/O cell communicates serial data from a target device to an initiator device. The I/O cell comprises a clock pad that receives a clock signal from the initiator device; a data pad that receives a data output signal from the target device; and a clock input buffer coupled to the clock pad. A flip-flop integrated in the I/O cell receives the clock signal directly from the clock input buffer, receives the data output signal from control logic of the target device, and outputs the data output signal in synchronization with the clock signal. A data output buffer receives the data output signal from the flip-flop and drives the data output signal to the data pad for access by the initiator device.