DAC Dummy Stages for Constant Reference Glitch Linearity
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Solution Overview
Problem
Conventional digital-to-analog converters (DACs) suffer from frequency-dependent distortion due to glitches in their reference voltages, leading to undesirable harmonic output frequencies when producing sinusoidal signals, which results in distortion of the analog output signal.
Innovation Solution
Incorporating a plurality of dummy stages that mimic the glitch behavior of the DAC stages, controlled by a logic circuit to maintain a constant total glitch on the reference voltages, thereby eliminating or reducing harmonic distortion in the analog output signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional DAC stages switch states to convert digital words to analog signals, then the analog output signal is produced, but harmonic distortion occurs due to varying glitch magnitudes on reference voltages
Solution Approach 1:
The patent creates dummy DAC stages that are identical copies of the actual DAC stages, including identical switch matrices and parasitic capacitances. These dummy stages copy the glitch behavior of the real stages without affecting the analog output signal, thereby canceling out the harmful harmonic distortion while maintaining productivity.
2Measurement precision
If more DAC stages switch states to accommodate changing digital words, then the conversion accuracy is maintained, but the glitch magnitude on reference voltages increases causing more distortion
Solution Approach 1:
The patent converts the harmful glitch effect into a beneficial cancellation mechanism. By introducing dummy stages that generate identical glitches to the real stages, the total glitch becomes constant rather than varying. This transforms the harmful varying glitch into a benign constant offset, eliminating harmonic distortion while preserving conversion accuracy.
3Object-generated harmful factors
If dummy stages are added to cancel glitch effects, then harmonic distortion is reduced, but device complexity increases
Solution Approach 1:
The patent segments the DAC system into two functional groups: actual DAC stages that produce the analog output signal and dummy DAC stages that generate canceling glitches. This segmentation allows the system to maintain the original conversion functionality while adding a separate distortion-cancellation mechanism, making the complexity manageable and modular.
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 solution effectively maintains a constant glitch on the reference voltages, eliminating or sharply reducing output distortion, ensuring high linearity and low noise in the analog output signal.
Implementation Method 1
the positive voltage rail couples through a corresponding resistor R1 to either a non-inverter input 135 or an inverting input 140 of an amplifier 125
Implementation Method 2
Every time an RDAC stage 115 switches between its switching states, the parasitic capacitances for its switch matrix 130 causes a glitch or disturbance on the positive and negative reference voltages
Data Source
AI summary
A digital-to-analog converter has both a plurality of DAC stages and a plurality of dummy stages. Each DAC stage causes a glitch or disturbance to a pair of reference voltages when the DAC stage changes its switching state. Each dummy stage also causes a similar glitch or disturbance to the pair of reference voltages when the dummy stage changes its switching state. The dummy stages are controlled to change their switching state responsive to how many DAC stages change their switching state such that a total glitch induced onto the reference voltages remains substantially constant across a succession of digital words converted by the digital-to-analog converter into an analog output signal.