Word Line Latch Circuit for Memory Signal Stability
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Solution Overview
Problem
Memory arrays experience errors due to fluctuations in word line signals during read operations, particularly as processing speeds increase, leading to instability in signal timing and reduced timing margins.
Innovation Solution
Incorporation of an inverted delay clock circuit and word line latches to generate a self-timed pulse during a first clock state, allowing the latches to store and stabilize address decode signals, isolating word lines from fluctuations and ensuring stable word line signals during memory access.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If processing circuit speeds increase to improve productivity, then memory access speed improves, but timing margins decrease and word line signal stability deteriorates
Solution Approach 1:
The patent applies preliminary action by capturing and latching the memory address signal before the word line activation occurs. The address capture circuit latches the address signal in response to a clock signal, ensuring the address is stable and captured before being used to activate the word line. This preliminary capture prevents timing issues and signal instability during high-speed operations.
Solution Approach 2:
The patent introduces an intermediary address capture circuit between the memory address input and the word line activation logic. This intermediary circuit includes latches that hold the address signal temporarily, allowing stable address decoding before word line activation. The intermediary buffer isolates the word line signals from fluctuations in the address bus, ensuring signal stability even at high processing speeds.
2Loss of time
If clock period is reduced to increase processing speed, then memory access time decreases, but time for signals to stabilize becomes insufficient
Solution Approach 1:
The address capture circuit performs preliminary action by latching the address signal early in the clock cycle, before the shorter time period expires. This ensures the address is captured and stabilized within the available time, allowing the rest of the memory access operation to proceed with stable signals even under reduced clock periods.
Solution Approach 2:
The patent segments the memory access operation into distinct phases: address capture phase, address decode phase, and word line activation phase. By using latches and separate circuit stages, each phase can be optimized independently, allowing the address capture to complete reliably within the shortened clock period while maintaining signal stability throughout the subsequent phases.
3Device complexity
If word line signals are activated directly from address decode without latching, then device complexity is reduced, but timing margins are insufficient and errors occur
Solution Approach 1:
The patent introduces an intermediary address latch circuit between the address decode logic and the word line activation. This intermediary latch holds the decoded address signal, providing a stable input to the word line activation logic. While this adds some circuit complexity, it dramatically improves reliability by preventing timing errors and signal fluctuations from causing read operation failures.
Solution Approach 2:
The address latch circuit provides beforehand cushioning by pre-stabilizing the address signal before it is used for word line activation. The latch absorbs timing variations and signal fluctuations, cushioning the critical word line activation step from potential errors. This preparatory stabilization ensures reliable operation even with varying timing conditions.
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AI summary
Memory array circuits including word line circuits providing word line signal stability are disclosed. In a memory access operation, the states of word line signals on word lines in the memory rows of the memory array may be based on the states of word line latches during a first clock state of a latch clock signal. The word line latches receive address decode signals generated from a decoded memory address. An inverted delay clock circuit generates a clock pulse from the latch clock signal. The word line latches store the address decode signals during the clock pulse and generate word line signals based on the stored address decode signals. The memory address is received from an address bus. Pass-through address capture latches maximize time available to a decoder for decoding the memory address and word line latches reduce fluctuations in the address signal being propagated to the word line signals.