Retention Flip-Flop Control Logic for Power-Down Data Hold
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Solution Overview
Problem
In digital circuits and SoCs, continuous power supply during idle or sleep modes leads to significant power consumption due to leak current, and temporarily disconnecting power to flip-flops results in data loss when power is restored.
Innovation Solution
A retention flip-flop design that includes a master latch, a slave latch, and control logic to generate control signals based on a clock signal and a power down mode signal, allowing the slave latch to maintain data during power down mode by forming a closed loop.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If power is continuously supplied to the flip-flop during idle or sleep modes, then data integrity is maintained, but power consumption increases due to leak current
Solution Approach 1:
The flip-flop is divided into two independent latches: a master latch that receives continuous power to maintain data integrity, and a slave latch that can be powered down to reduce leakage. The control logic segments the power supply management, allowing selective power distribution to different parts of the flip-flop based on operational mode.
Solution Approach 2:
A control logic unit acts as an intermediary between the power supply and the latches, managing power distribution based on operational mode. This control logic generates control signals that enable the master latch to retain data during power-down modes while preventing the slave latch from leaking current when not in use.
2Use of energy by moving object
If power is temporarily disconnected from the flip-flop during idle or sleep modes, then power consumption is reduced, but data is lost when power is restored
Solution Approach 1:
The master latch is prepared in advance to receive and hold data before power is disconnected from the slave latch. During the transition to power-down mode, the control logic ensures that valid data is already present in the master latch, which has continuous power supply, thereby preventing data loss when the slave latch is powered down.
Solution Approach 2:
The system discards the slave latch's data storage function during power-down modes, relying instead on the master latch that maintains data with continuous power. When power is restored, the slave latch recovers its functionality and retrieves data from the master latch, effectively recovering the complete data storage capability.
3Reliability
If the slave latch is designed to maintain data during power down mode by forming a closed loop, then data integrity is preserved, but circuit complexity increases
Solution Approach 1:
The slave latch is designed with dynamic characteristics, allowing it to switch between two operational states: a transparent state during normal operation where data flows from master to slave, and a retention state during power-down modes where feedback loops are activated to maintain data. This dynamic behavior enables data retention without requiring a permanently complex circuit structure.
Solution Approach 2:
The slave latch is designed to perform multiple functions: data storage during normal operation, data retention during power-down modes, and power gating to reduce leakage. By integrating these multiple functions into a single circuit block with controllable feedback paths, the design achieves data retention capability without proportionally increasing overall circuit complexity.
Data Source
AI summary
A low-power retention flip-flop is provided. The low-power retention flip-flop may include: a master latch configured to output an input signal based on first control signals; a slave latch configured to output the signal from the master latch based on second control signals; and a control logic configured to generate the first control signals based on a clock signal, and provide the generated first control signals to the master latch, and generate the second control signals based on the clock signal and a power down mode signal, and provide the generated second control signals to the slave latch.