DAC Element Matching Using Complementary Error-Canceling Groups
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Solution Overview
Problem
Digital-to-analog converters (DACs) using single-bit elements suffer from nonlinearities and noise due to varying errors in the DAC elements, which are not effectively addressed by existing dynamic element matching (DEM) encoders that either introduce or exacerbate noise.
Innovation Solution
A reduced-effort DEM encoder and multiplexer arrangement that generates a noise-corrected control signal by mapping asserted bits to complementary groups of single-bit DAC elements with errors that partially cancel, reducing both nonlinearities and noise in the analog output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If single-bit DAC elements are used to simplify the converter structure, then device complexity is reduced, but manufacturing precision deteriorates due to varying errors in the DAC elements causing nonlinearities and noise
Solution Approach 1:
The patent segments the DAC elements into complementary groups where each group contains elements with errors that partially cancel each other. By dividing the single-bit DAC elements into these specialized groups and using a multiplexer to selectively activate complementary pairs, the system maintains simplicity while compensating for manufacturing variations through the grouped error-cancellation approach.
Solution Approach 2:
The patent changes the operational parameters by dynamically selecting which DAC elements are activated based on the input signal and error characteristics. The multiplexer circuit modifies the control signal to direct asserted bits to complementary groups, effectively changing which physical elements are used for each conversion operation, thereby compensating for fixed manufacturing errors.
2Manufacturing precision
If dynamic element matching (DEM) encoders are used to address element errors, then manufacturing precision is improved, but object-generated harmful factors worsen due to introduced or exacerbated noise
Solution Approach 1:
The patent converts the harmful effect of varying DAC element errors into a beneficial cancellation effect by pairing complementary elements. Instead of trying to eliminate the errors through complex encoding, the system uses the multiplexer to activate pairs of elements whose errors naturally cancel each other, turning the previously harmful variation into a useful error-compensation mechanism that reduces both nonlinearities and noise.
Solution Approach 2:
Rather than using a DEM encoder to randomly permute element activation to average out errors, this patent inverts the approach by deterministically assigning elements to complementary groups and using a multiplexer to select from these pre-organized pairs. This reversal of the conventional DEM strategy eliminates the noise introduction problem while maintaining error compensation.
3Manufacturing precision
If conventional DEM encoding is used to randomize element selection, then manufacturing precision is improved through error averaging, but object-generated harmful factors worsen due to increased noise in the analog output
Solution Approach 1:
The patent applies preliminary action by pre-organizing DAC elements into complementary groups before the conversion operation. The multiplexer is configured in advance to direct control signals to these pre-established pairs, ensuring that error cancellation occurs systematically rather than relying on randomization. This preliminary organization eliminates the noise generation that occurs with conventional DEM while preserving the error averaging benefit.
Data Source
AI summary
An example digital-to-analog converter (DAC) circuit may comprise a plurality of single-bit DAC elements, an encoder circuit, and a multiplexer circuit. The encoder circuit may be configured to generate a control signal, where a number of asserted bits in the control signal is based at least in part on a digital input signal and an asserted bit pattern of the control signal is based at least in part on a random signal. The multiplexer circuit may be configured to modify the control signal to generate a noise-corrected control signal having a noise-corrected bit pattern. The noise-corrected bit pattern may direct a first asserted bit of the noise-corrected control signal to activate a first single-bit DAC element and a second asserted bit of the noise-corrected control signal to activate a second single-bit DAC element, where the first single-bit DAC element and the second single-bit DAC element having respective errors that at least partially cancel.