Time-Based Sensing Circuit for Low Power Resistive Memory
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Solution Overview
Problem
Conventional methods for sensing resistance in programmable resistive devices require high supply voltage and current, making it difficult to operate under low voltage and low current conditions, which is a challenge in IoT and other low-power applications.
Innovation Solution
A time-based sensing method using capacitors charged and discharged through programmable resistive elements, where the resistance is determined by the time delay to reach a predetermined voltage, allowing for low voltage and low current operation without relying on MOS device threshold voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional voltage sensing method is used to sense PRE resistance, then measurement precision is improved, but use of energy increases due to high voltage and high current requirements
Solution Approach 1:
The patent replaces the conventional voltage-based sensing mechanism with a time-based sensing mechanism. Instead of using voltage amplification (which requires high voltage and current), the system uses a capacitor discharge time measurement to determine resistance. This substitution of the sensing principle allows operation at low voltage and low current while maintaining measurement capability.
Solution Approach 2:
The patent changes the sensing parameter from voltage to time. By measuring the time constant of capacitor discharge through the PRE, the system can determine resistance without requiring high voltage or current. This parameter transformation enables low-power operation while maintaining sensing accuracy.
2Measurement precision
If high voltage is applied to bias MOS devices in high gain region, then measurement precision is improved, but use of energy increases substantially
Solution Approach 1:
The patent eliminates the need for MOS device biasing by replacing voltage-based sensing with time-based sensing. The capacitor discharge time measurement does not require high voltage or current, thus avoiding the energy consumption associated with biasing MOS devices in high gain regions.
Solution Approach 2:
The patent extracts and removes the MOS device biasing requirement from the sensing process. By using a simple capacitor discharge time measurement, the system eliminates the need for complex voltage amplification circuits and high current consumption, retaining only the essential sensing function.
3Measurement precision
If conventional voltage amplification scheme is used, then measurement precision is improved, but device complexity increases due to multiple MOS devices
Solution Approach 1:
The patent extracts and removes the complex voltage amplification circuitry from the sensing system. By using time-based sensing with a single capacitor and resistor, the system eliminates the need for multiple MOS devices and complex circuit architecture, reducing device complexity while maintaining measurement capability.
Solution Approach 2:
The patent replaces the complex voltage amplification mechanism with a simple time measurement approach. This substitution dramatically reduces the number of components needed, as only a capacitor, resistor, and timing mechanism are required, eliminating the need for multiple MOS devices and complex circuitry.
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
Enables efficient resistance sensing in programmable resistive memory cells with low power consumption, suitable for IoT applications, by converting resistance into a logic state using time-based discharging and comparison with a reference voltage.
Implementation Method 1
a capacitor is charged to near a supply voltage level during a first period of time. Then, the capacitor is discharged through a resistance over a second period of time. A voltage at the discharging capacitor can be compared with a reference voltage to change a memory read output. The time for an output logic device to change its output is determined by a product of the resistance and capacitance.
Implementation Method 2
The resistance of a PRE in a PRD device needs to be converted into a logic level after reading the PRD cell. This can be achieved by using a sensing circuit or sense amplifier (SA).
Data Source
AI summary
A time-based sensing circuit to convert resistance of a programmable resistive element into logic states is disclosed. A programmable resistive memory has a plurality of programmable resistive devices. At least one of the programmable resistive devices can have at least one programmable resistive element (PRE) that is selectively accessible via a wordline and a bitline. The bitline can be coupled a capacitor and the capacitor can be precharged and discharged. By comparing the discharge rate of the capacitor to discharge rate of a reference capacitor in a reference unit (e.g., reference cell, reference resistance, reference selector, etc.), the PRE resistance can be determined larger or smaller than a reference resistance and then converting the PRE resistance into a logic state.