Sense Amplifier Flip-Flop Layout for Setup Time Violations
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Solution Overview
Problem
High-speed semiconductor integrated circuits face setup time violations, which existing solutions address by increasing data path drive or adding buffers, resulting in significant increases in block area, making them unsuitable for standard cell libraries and causing skew between data arcs.
Innovation Solution
A sense amplifier flip-flop (SAFF) design with an equal number of p-type and n-type metal oxide semiconductor transistors in the master latch, coupled with a clock inverter that generates an inverted clock signal, allowing for reduced block area without additional buffers or data inverters, thus preventing setup time violations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If extra feedback buffers are added to avoid setup time violations, then setup time violations are fixed, but layout area increases significantly
Solution Approach 1:
The patent removes the extra feedback buffers from the traditional sense amplifier flip-flop design. By extracting these unnecessary buffering elements, the design achieves setup time violation resolution without the area penalty of additional buffers, directly addressing the contradiction between reliability improvement and area increase.
Solution Approach 2:
The patent inverts the traditional approach by using an equal number of PMOS and NMOS transistors in the master latch rather than using dominating NMOS transistors. This inversion of the transistor balance resolves setup time violations through improved signal symmetry and reduced skew, eliminating the need for area-consuming feedback buffers.
2Reliability
If dominating number of NMOS transistors are used in sense-amplifier, then sense amplifier functionality is achieved, but layout area increases significantly
Solution Approach 1:
The patent applies asymmetry in a controlled manner by maintaining an equal number of PMOS and NMOS transistors in the master latch, creating a balanced design that reduces area while preserving sense amplifier functionality. This symmetric configuration eliminates the area overhead associated with dominating NMOS designs.
Solution Approach 2:
The patent changes the transistor composition parameter from dominating NMOS to an equal mix of PMOS and NMOS. This parameter change in the transistor balance resolves setup time violations and reduces layout area while maintaining the sense amplifier's core functionality.
3Reliability
If data inverters are added to resolve setup time violations, then setup time violations are fixed, but skew between data arc and data_bar arc increases
Solution Approach 1:
The patent inverts the traditional approach by eliminating data inverters and instead using an equal number of PMOS and NMOS transistors in the master latch. This inversion resolves setup time violations through improved signal symmetry, thereby reducing skew between data arcs rather than increasing it.
Data Source
AI summary
A method and a sense amplifier flip-flop (SAFF) for fixing setup time violations in an integrated circuit (IC) design. The SAFF includes a master latch coupled to a slave latch, wherein the master latch includes a sense amplifier and the SAFF is configured with an equal number of p-type metal oxide semiconductor (PMOS) transistors and n-type metal oxide semiconductor (NMOS) transistors to reduce block area of an integrated circuit (IC). The method includes receiving a clock signal, receiving a data signal, applying the data signal to the sense amplifier when the clock signal is at a low level, wherein a portion of the sense amplifier is responsive to the inverted clock signal, storing a value of the data signal in the slave latch when the clock signal transitions from the low level to the high level, and providing an output signal from the slave latch.