Latch Transistor Body Biasing for Fast, Reliable Voltage Sensing
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Solution Overview
Problem
Sensing circuitry using latch transistors with body regions insulated from the substrate faces issues with the 'history effect' leading to incorrect operation and increased power consumption due to forward-biased diodes, which existing solutions attempt to mitigate but result in noise and additional power consumption.
Innovation Solution
The introduction of body biasing circuitry that precharges the body region of latch transistors with a voltage derived from input lines before sensing and allows the voltage to float during sensing, preventing forward-biased diodes and reducing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the body region of latch transistors is insulated from the substrate to reduce capacitive loading and improve switching speed, then switching speed is improved, but the history effect causes voltage variation on the body region leading to incorrect operation
Solution Approach 1:
The body region is precharged to a reference voltage (e.g., ground for NMOS, VDD for PMOS) before the sensing operation begins. This preliminary action establishes a known initial voltage state that eliminates the history effect, ensuring reliable operation while maintaining the speed benefits of insulated body regions.
Solution Approach 2:
The body biasing is made dynamic rather than static. The body region voltage is temporarily set to a reference level only during the sensing operation, then allowed to float or be reset afterward. This dynamic approach removes the history effect during critical sensing while minimizing overall impact on transistor performance.
2Reliability
If the body region is biased to a fixed reference voltage to remove the history effect, then correct operation is improved, but MOSFET threshold voltage increases causing delayed switching and increased detection time
Solution Approach 1:
The reference voltage is applied to the body region only preliminarily, before sensing begins, and then removed. This temporary precharging removes the history effect without maintaining the threshold voltage shift during sensing, thus avoiding delayed switching while ensuring correct initial operation.
Solution Approach 2:
The body biasing is applied periodically only when needed - specifically during the precharge phase before each sensing operation. This periodic application removes the history effect at the right moment while minimizing the duration of threshold voltage shifts, thereby reducing overall detection time.
3Reliability
If body biasing is applied to remove the history effect, then correct operation is improved, but power consumption increases due to forward-biased diodes
Solution Approach 1:
The body region is precharged to the reference voltage only briefly before sensing begins, then the connection is disconnected and the body voltage is allowed to float. This limited-duration precharging removes the history effect while minimizing the time that forward-biased diodes conduct, thereby reducing overall power consumption.
Solution Approach 2:
The body biasing configuration is made dynamic - switching from a reference-voltage-connected state during precharge to a floating state during sensing. This dynamic reconfiguration ensures correct operation during the critical precharge phase while eliminating unnecessary power consumption during the sensing phase when biasing is no longer needed.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively eliminates the history effect, reduces power consumption, and minimizes noise by ensuring the body region is not connected to any voltage during sensing, enhancing switching speed and accuracy.
Implementation Method 1
reduces the capacitive loading on the transistor terminals when compared with latch transistors formed from non-insulated technologies
Implementation Method 2
reducing resistive leakage to the substrate
Implementation Method 3
body biasing circuitry which prior to the sensing stage of operation causes a voltage to be applied to the body region that is derived from the voltage on one of said at least one input lines
Implementation Method 4
this can give rise to significant extra power consumption due to the forward-biased diode current
Data Source
AI summary
Sensing circuitry and a method of operating such sensing circuitry are provided. The sensing circuitry has voltage change detection circuitry for detecting a change in voltage on at least one input line and for producing at least one output signal indicative of that change during a sensing stage of operation. The voltage change detection circuitry comprises at least one latch transistor having a body region insulated from a substrate. Further, body biasing circuitry is provided which, prior to the sensing stage of operation, causes a voltage to be applied to the body region that is derived from the voltage on one of said at least one input lines. Then, during the sensing stage of operation, the body biasing circuitry causes the voltage of the body region to float. Such an arrangement enables removal of the history effect that can sometime affect such latch transistors, whilst alleviating power consumption and noise issues that can occur in certain known sensing circuits.