RRAM Crossbar Programming With IDAC-Based Linear Current Control
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Solution Overview
Problem
Existing crossbar circuits face challenges in precisely controlling programming currents for resistive random-access memory (RRAM) devices due to the parabolic relationship between current and gate voltage, especially in smaller transistors, leading to compromised control over conductance values.
Innovation Solution
Implementing current-mode digital-to-analog converters (IDACs) to generate linearly controlled output currents for RRAM devices, allowing precise programming of conductance values without relying on transistors for current control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If transistors are used to control programming currents in crossbar circuits, then device complexity is reduced, but manufacturing precision deteriorates due to parabolic relationship between current and gate voltage
Solution Approach 1:
The patent replaces the transistor-based voltage control mechanism with a current-mode digital-to-analog converter (IDAC) that directly generates programming currents. This substitution eliminates the parabolic relationship between gate voltage and current that plagues transistor-based control, providing a linear and precise control mechanism for RRAM conductance programming while maintaining reasonable device complexity through integrated IDAC circuits.
Solution Approach 2:
The invention changes the control parameter from voltage (gate voltage of transistors) to current (IDAC output current). By using current-mode operation instead of voltage-mode operation, the system achieves linear control characteristics where the programming current is directly proportional to the digital input code, eliminating the parabolic distortion inherent in transistor-based voltage control and significantly improving conductance programming precision.
2Area of moving object
If smaller transistors are used in crossbar circuits, then device area is reduced, but measurement precision deteriorates due to compromised current control
Solution Approach 1:
The patent replaces the transistor current control mechanism with an IDAC-based current source. This substitution is particularly beneficial for smaller transistors where the parabolic relationship between gate voltage and current becomes more pronounced and harder to control. The IDAC provides accurate current control independent of transistor size, enabling precise conductance programming even in compact crossbar circuit configurations.
3Ease of operation
If voltage-mode control is used in crossbar circuits, then ease of operation is maintained, but manufacturing precision deteriorates due to parabolic current-voltage relationship
Solution Approach 1:
The invention transitions from voltage-mode control to current-mode control by introducing IDACs. The IDAC accepts a simple digital input code and directly outputs the corresponding programming current, maintaining ease of operation through digital control while achieving linear and precise current control. This eliminates the parabolic relationship inherent in voltage-mode transistor control, where small voltage changes at the gate produce non-linear and difficult-to-predict current variations.
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
The use of IDACs enables precise and linear control of programming currents, ensuring high linearity and accuracy in programming RRAM devices, particularly in smaller transistors, thereby improving the performance of crossbar circuits.
Implementation Method 1
one or more current digital-to-analog converters (IDACs) configured to perform digital-to-analog conversion, wherein a first IDAC of the plurality of IDACs is selectively connected to a first word line of the plurality of word lines or a first bit line of the plurality of bit lines
Implementation Method 2
the first RRAM device is programmed to a first conductance value in response to the application of the first output current
Data Source
AI summary
The present disclosure relates to crossbar circuits utilizing resistive random-access memory (RRAM) devices. A crossbar circuit may include a plurality of word lines intersecting with a plurality of bit lines, and a plurality of cross-point devices. Each of the cross-point devices is connected to one of the word lines and one of the bit lines and includes a resistive random-access memory (RRAM) device. The crossbar circuit may further include one or more current digital-to-analog converters (IDACs) configured to perform digital-to-analog conversion. The IDACs are selectively connected to the word lines or the bit lines to provide programming signals to program the RRAM devices to predetermined conductance values. The IDACs may linearly control the compliance currents of the RRAM devices to program the RRAM devices to multiple linearly separated conductance values.