D Flip-Flop Latch Topology With Reduced Clock Load
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Solution Overview
Problem
Existing D flip-flops consume significant power due to high clock network loading, leading to energy dissipation and increased electromigration, which can cause system glitches and device failure.
Innovation Solution
A D flip-flop design with reduced clock network loading connections, where the feedback path does not receive the clock signal, and transistors are maintained in a weakly on state to minimize power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the clock signal is distributed to all switching devices in the D flip-flop, then the flip-flop operates reliably, but the clock network consumes excessive power and creates high capacitive load
Solution Approach 1:
The patent extracts the clock signal distribution only to the essential switching devices (first and second transistor sets) while removing it from the feedback path transistor sets. This selective extraction maintains the core latching function reliability while significantly reducing the clock network's capacitive load and power consumption.
Solution Approach 2:
The patent segments the transistor sets into two categories: those requiring clock signals (first and second transistor sets for data latching) and those not requiring clock signals (third and fourth transistor sets for feedback). This segmentation allows differential clock distribution strategy that optimizes power consumption while maintaining functional reliability.
2Reliability
If multiple transistor sets receive clock signals, then the latching function is robust, but the capacitive load on the clock network increases
Solution Approach 1:
The patent extracts the clock signal connection from the feedback path transistor sets (third and fourth transistor sets), keeping only the essential latching transistors (first and second transistor sets) connected to the clock network. This reduction directly decreases the total capacitive load while preserving the robust latching function through the remaining clocked transistors.
3Reliability
If the feedback path uses strongly on transistors, then the feedback signal is strong, but the power consumption and electromigration increase
Solution Approach 1:
The patent changes the operating parameter of the feedback transistors from strongly on to weakly on by applying a reduced gate voltage (fraction of supply voltage). This parameter change creates a weak feedback signal that is sufficient to maintain the latched state without causing excessive current flow, thereby reducing electromigration while maintaining feedback functionality.
4Loss of energy
If transistors are kept weakly on to reduce power, then energy dissipation decreases, but the feedback signal strength may be insufficient
Solution Approach 1:
The patent optimizes the gate voltage parameter for the feedback transistors to a specific fraction of the supply voltage, creating a weak but sufficient feedback signal. This parameter optimization ensures that the weakly on transistors consume minimal power while still generating enough feedback signal strength to reliably maintain the latched state.
Solution Approach 2:
The patent introduces an intermediary voltage level (fraction of supply voltage) as the gate voltage for feedback transistors, which acts as a mediator between the fully on state (high power) and fully off state (no feedback). This intermediary voltage creates the optimal weak feedback signal that balances power consumption and signal sufficiency.
Data Source
AI summary
A latch for a flip-flop or other circuit which requires fewer signal inputs than prior latch designs to reduce power consumption. The latch comprises a first transistor set is switching element and is configured to receive clock signals from a clock network and an input signal. A second transistor receives the input signal from the first transistor set and is configured as a first data buffer to create a latch output. A feedback path includes a third transistor set in series with a resistor or transistor pair. The feedback path receives the latch output and generates a feedback signal, which is provided to the first transistor set. The resistor or transistor pair is selected to establish the feedback signal at a magnitude that is sufficiently large to maintain the state of the latch but sufficiently small to allow a change in the input signal to change the latch output.