PRA-DAC Current Compensation for Code-Independent Linearity
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Solution Overview
Problem
Parallel Resistors Architecture (PRA) digital-to-analog converters (DACs) suffer from code-dependent current consumption, which worsens their linearity and integral non-linearity due to parasitic access resistance, limiting their use to low-resolution applications.
Innovation Solution
A current compensation circuit and an optimized current compensation circuit are introduced to balance code-dependent current consumption in PRA-DACs, making the voltage drop across parasitic access resistance independent of the digital code and allowing for a single resistor to achieve well-matched compensation, thus improving linearity without the need for costly calibration or oversized resistors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If PRA-DAC is used to achieve constant output impedance and inherent monotonicity, then device performance is improved, but code dependent current consumption worsens linearity and integral non-linearity
Solution Approach 1:
A compensation circuit is introduced as an intermediary component that generates a compensation current to counteract the code-dependent current consumption in the PRA-DAC. This mediator circuit includes a compensation current source and switching elements that respond to the digital input code, producing a compensating current that flows through the parasitic access resistance to cancel its harmful effect on linearity.
Solution Approach 2:
The compensation circuit operates based on feedback from the digital input code to the compensation current source. The compensation current is dynamically adjusted according to the input code to maintain constant total current consumption, thereby stabilizing the voltage drop across parasitic resistance and improving linearity through code-dependent feedback control.
2Manufacturing precision
If calibration process is used to improve linearity, then manufacturing precision is improved, but device complexity and cost increase
Solution Approach 1:
The PRA-DAC with compensation circuit achieves self-correction of linearity errors through the compensation circuit that automatically generates the appropriate compensation current based on the input code. The system serves itself by internally compensating for its own deficiencies without requiring external calibration processes or additional matching networks.
3Manufacturing precision
If resistor oversizing is used to improve linearity, then manufacturing precision is improved, but device area increases
Solution Approach 1:
The invention changes the operational parameters by introducing a dynamic compensation current that varies with the input code. This parameter change allows the use of standard-sized resistors while achieving high linearity through the compensation mechanism, eliminating the need to oversize resistors to compensate for parasitic effects.
4Manufacturing precision
If weighted resistors compensation network is used to balance current consumption, then linearity is improved, but device complexity and area increase
Solution Approach 1:
The compensation function is segmented and distributed across multiple switching elements and current sources that operate in parallel. Each segment of the compensation circuit corresponds to a specific portion of the digital input code, allowing the total compensation current to be constructed from modular segments rather than requiring a single complex weighted resistor network.
Data Source
AI summary
A current compensation circuit and an optimized current compensation circuit are disclosed for a Parallel Resistors Architecture (PRA) digital-to-analog converter (DAC). The circuits are used to balance code dependent current consumption of the PRA-DAC.