Sequential Latch Circuit Topology for Faster Clocked Operation
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Solution Overview
Problem
Conventional sequential circuits face challenges in achieving high-speed operation and minimizing the influence of clock changes, leading to limitations in clock frequency and setup time.
Innovation Solution
The proposed sequential circuit design includes a first stage and a second stage, each with transistors configured to charge and discharge nodes in response to a clock signal and logic signals, with combinational logic generating logic signals based on node voltages and data, ensuring that one node is not discharged when the other is, and vice versa, utilizing a 2-stack structure for NMOS transistors to enhance discharge speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional sequential circuits use traditional charging and discharging mechanisms, then the circuit structure is simple, but the operation speed is limited and setup time is large
Solution Approach 1:
The sequential circuit is divided into two distinct stages: a first stage with a first node for charging/discharging operations, and a second stage with a second node for latching operations. This segmentation allows each stage to be optimized independently, with the first stage focusing on fast switching and the second stage on stable data holding, thereby increasing overall operation speed without excessive complexity
Solution Approach 2:
A combinational logic circuit is introduced as an intermediary between the first node and the second node. This combinational logic generates control signals that coordinate the charging and discharging operations of both nodes, ensuring that they operate in a complementary manner. The intermediary logic enables fast switching while maintaining circuit stability, resolving the contradiction between speed and complexity
2Productivity
If the circuit operates at higher clock frequencies, then productivity increases, but the influence of clock changes and setup time requirements worsen
Solution Approach 1:
The circuit utilizes periodic clock signals to control the charging and discharging of nodes in a systematic manner. The first node is charged/discharged during one clock phase while the second node maintains its state during the same phase, and vice versa in alternating phases. This periodic coordination allows the circuit to operate reliably at higher clock frequencies by ensuring that each node has sufficient time to complete its transition before the next clock edge
Solution Approach 2:
The combinational logic circuit generates control signals in advance based on the current state of the first node and input data, preparing the second node for its next state before the clock edge arrives. This preliminary action reduces the setup time requirement and allows the circuit to tolerate higher clock frequencies with minimal impact from clock variations
3Ease of operation
If both nodes are discharged simultaneously, then the circuit structure is simple to control, but harmful effects occur due to simultaneous discharge conflicts
Solution Approach 1:
Instead of allowing both nodes to be discharged simultaneously through simple control, the invention inverts the approach by using the state of one node to control the discharge of the other. The combinational logic ensures that when the first node is discharged, the second node is prevented from discharging, and vice versa. This inverted control mechanism eliminates discharge conflicts while maintaining relatively simple control logic through complementary switching
Data Source
AI summary
In a sequential circuit, a first stage is configured to charge a voltage of a first node in response to a clock, and to discharge the voltage of the first node in response to the clock, a voltage of a second node, and data; a second stage is configured to charge the voltage of the second node in response to the clock, and to discharge the voltage of the second node in response to the clock and a logic signal; a combinational logic is configured to generate the logic signal based on the voltage of the first node, the voltage of the second node, and the data; and a latch circuit is configured to latch the voltage of the second node in response to the clock.