High-Speed DAC Switching With Positive Feedback for Low Distortion
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
High-speed digital-to-analog converters (DACs) face challenges with distortion and increased power consumption at high frequencies, leading to code-dependent glitching and higher power consumption that increases linearly with clock frequency.
Innovation Solution
The implementation of a DAC with switch drivers and output switches that include positive feedback circuitry to address floating node issues, reduce latency, and operate in current steering modes with bi-polar quad or hex switching schemes, along with dual- or tri-level decoding formats to manage current flow effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If high-speed DACs operate at high clock frequencies, then conversion speed is improved, but power consumption increases linearly with clock frequency
Solution Approach 1:
The patent employs periodic clocked switching actions where switches are activated only during specific clock phases rather than continuously. The switch driver uses clock signals to periodically control the switching of current sources, reducing average power consumption while maintaining high-speed conversion capability through efficient use of switching cycles.
Solution Approach 2:
The patent implements dynamic switching schemes where the DAC operates in different modes (single-ended or differential) based on input conditions. The switch driver dynamically controls current steering based on digital input codes, allowing the circuit to adapt its power consumption and performance characteristics to match the actual conversion requirements rather than operating at maximum power continuously.
2Speed
If high-speed DACs operate at high clock frequencies, then conversion speed is improved, but distortion increases due to code-dependent glitching
Solution Approach 1:
The patent implements feedback mechanisms through differential switching schemes where the output is controlled to minimize glitches. The switch driver uses feedback from the digital input codes to control the switching timing and sequence, ensuring that current transitions are synchronized and balanced, thereby reducing code-dependent glitching and improving output linearity at high speeds.
Solution Approach 2:
The patent employs asymmetric switching schemes where different switching sequences are applied for different current sources based on the digital input code. By asymmetrically controlling the switching of individual current sources in a current-steering DAC, the patent balances the total current transitions and reduces glitching artifacts while maintaining high conversion speed.
3Reliability
If positive feedback circuitry is added to switch drivers, then floating node issues are resolved and latency is reduced, but device complexity increases
Solution Approach 1:
The patent introduces positive feedback circuitry in the switch driver to resolve floating node issues that occur during switching transitions. The feedback connections provide defined voltage paths during critical switching moments, ensuring stable node voltages and reducing uncertainty in the switching behavior. This feedback mechanism is integrated into the existing switch driver architecture with minimal additional components.
Solution Approach 2:
The patent implements preliminary action by pre-charging or pre-discharging certain nodes before the main switching event occurs. The positive feedback circuitry is configured to act in advance of the primary switching transition, preparing the voltage states of critical nodes to prevent floating conditions. This preliminary action reduces latency by eliminating the need for slow discharge paths during switching transitions.
Data Source
Figure 1
Figure 2
Figure 3A
AI summary
A digital-to-analog converter (DAC) capable of operating in radio frequency (RF) with linear output, low distortion, low power consumption, and input data independence. The DAC includes switch drivers and output switches driven by the switch drivers. The switch drivers include pairs of outputs, and positive feedback circuitries coupled between respective pairs of outputs. The output switches are arranged between a first current source configured to push current to the DAC's outputs and a second current source configured to pull current from the DAC's outputs. Different output switches are configured to push current to and pull current from the DAC's outputs in accordance with rising edges and falling edges, respectively.