Current-Source DAC Randomization for Lower Spurious Interference
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Solution Overview
Problem
Conventional digital-to-analog converters suffer from inconsistent current values generated by internal current sources, leading to spurious component interference, which results in poor performance in Integral Non-Linearity (INL) and Spurious Free Dynamic Range (SFDR).
Innovation Solution
A digital-to-analog converter incorporating a current source module, decoder, and random number generator, where the decoder generates a control signal based on a digital input signal and an indication signal produced by a change indicator, to minimize spurious component interference by randomly shifting the selection of current sources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple internal current sources are used to generate analog signals, then the conversion capability is improved, but current value inconsistency causes spurious component interference
Solution Approach 1:
The patent applies dynamic element matching by randomly selecting and shuffling current source elements during operation. The system dynamically adjusts which current sources are activated in each conversion cycle, preventing consistent pairing of mismatched current sources with specific digital input codes. This dynamic randomization eliminates spurious components while maintaining accurate differential non-linearity (DNL) and integral non-linearity (INL) performance.
2Object-generated harmful factors
If current source values are made consistent, then spurious component interference is reduced, but device complexity increases
Solution Approach 1:
The patent introduces a random number generator and element shuffling logic as intermediary components between the digital input and current source selection. These intermediaries randomly permute the mapping between digital codes and current source combinations, effectively decoupling the fixed mismatch patterns from the conversion process. This approach reduces spurious components without requiring precise matching of current source values.
3Object-generated harmful factors
If random number generator and change indicator are added, then spurious component interference is reduced, but device complexity increases
Solution Approach 1:
The patent changes the operational parameters of the current source module by introducing randomization in the element selection and shuffling process. The random number generator produces varying selection patterns that change the effective parameters of current source activation dynamically. This parameter randomization eliminates spurious components while the added complexity remains manageable through efficient implementation of the randomization logic.
Data Source
AI summary
A digital-to-analog converter and an operation method thereof are provided. The digital-to-analog converter includes a current source module, a decoder, a change indicator, and a random number generator. The decoder is coupled to the current source module and receives a digital input signal. The change indicator is coupled to the decoder and provides an indication signal to the decoder. The random number generator is coupled to the change indicator and provides a random number signal to the change indicator. The change indicator generates an indication signal according to the random number signal, and the decoder generates a control signal to the current source module according to the digital input signal and the indication signal, so that the current source module generates an analog output signal corresponding to the digital input signal according to the control signal.