Latch-Based Serial Output Buffer for Lower Propagation Delay
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Solution Overview
Problem
Conventional serial output ports in integrated circuits face significant latency issues due to propagation delays in flip-flop stages, which adversely affect access and setup times, especially at high data rates required in modern systems like hard disk drives.
Innovation Solution
A serial output port design that incorporates a latched buffer as the last stage, eliminating the need for an external output buffer and reducing propagation delay by integrating the output buffer directly into the last shift register stage, utilizing CMOS technology to enhance drive capability and reduce latency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional flip-flop stages are used in serial output ports, then the circuit structure is simple and reliable, but propagation delay increases and access time worsens
Solution Approach 1:
The patent merges the output buffer functionality directly into the last flip-flop stage by adding an enable signal-controlled output buffer. This integration eliminates the need for a separate external output buffer, reducing the number of components and interconnections while improving access time by approximately 2 nanoseconds without compromising circuit reliability.
2Power
If conventional flip-flop stages with external output buffers are used, then drive capability is sufficient, but propagation delay increases and latency time worsens
Solution Approach 1:
The output buffer is integrated into the last flip-flop stage with shared enable signal control, merging two previously separate functions into a single unified stage. This reduces the number of discrete components and interconnections, thereby reducing propagation delay and latency time while maintaining sufficient drive capability for external terminals.
3Quantity of substance
If more flip-flop stages are used to increase shift register capacity, then data storage capacity increases, but propagation delay accumulates and access time worsens
Solution Approach 1:
The integrated output buffer in the last flip-flop stage is pre-configured with enable signal control, allowing data to be prepared and buffered in advance within the same stage. This preliminary action within the shift register eliminates the need for additional external buffering stages, reducing cumulative propagation delay while maintaining data storage capacity.
4Reliability
If separate external output buffer is used, then buffer functionality is provided, but device complexity increases and manufacturing becomes more difficult
Solution Approach 1:
The output buffer functionality is merged into the last flip-flop stage by sharing the enable signal control logic and integrating the buffer circuit within the same physical stage. This eliminates the need for a separate external output buffer component, reducing device complexity and simplifying manufacturing while preserving essential buffer functionality.
Data Source
AI summary
An integrated circuit (22) having a serial interface (25) with improved access times is disclosed. The serial interface (25) includes a serial output port arranged as a shift register of flip-flop stages (321 through 32n) and a last output latch stage (320). The last output latch stage (320) includes an integral output buffer (33), and as such is constructed differently from the other output flip-flops (321 through 32n), which include master and slave latches. No external output buffer is then required; this last output latch stage (320) directly drives the output terminal and the external serial data line (SDATA).