DAC Noise Shaping via Virtual Ground Switching
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Solution Overview
Problem
Low frequency noise from resistors and current sources in digital-to-analog converters (DACs) reduces system performance, and existing solutions either increase component size or use expensive materials to mitigate this issue.
Innovation Solution
Implementing a switching algorithm that couples resistors or current sources to positive and negative virtual ground nodes, allowing for differential cancellation of flicker noise by quickly switching between these nodes, thereby reducing noise in the signal band.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the size of resistors or current sources is increased to reduce low frequency noise, then noise performance is improved, but area and cost increase
Solution Approach 1:
The patent applies periodic switching action by rapidly toggling the resistor connections between positive and negative virtual ground nodes at a frequency higher than the noise corner frequency. This periodic switching shapes the noise spectrum, pushing low-frequency noise to higher frequencies where it can be filtered, thereby reducing in-band noise without increasing resistor area
Solution Approach 2:
The patent changes the operating parameters by switching the resistor connection nodes dynamically between positive and negative virtual ground. This parameter change transforms the noise characteristics through noise shaping, allowing smaller resistors to achieve the same noise performance that would otherwise require larger components
2Object-affected harmful factors
If expensive elements like silicon chromium resistors are used to eliminate flicker noise, then noise performance is improved, but cost increases
Solution Approach 1:
The patent converts the harmful low-frequency flicker noise into a beneficial shaped noise spectrum by using periodic switching. The switching action modulates the noise to higher frequencies, transforming the problematic low-frequency noise into high-frequency noise that can be easily filtered, thereby eliminating the need for expensive special materials
Solution Approach 2:
The patent substitutes material-based noise reduction (using special resistor materials like silicon chromium) with a circuit-based approach (periodic switching between virtual ground nodes). This substitution achieves the same noise reduction effect through electrical switching rather than relying on expensive special materials
3Area of stationary object
If resistor width is reduced to decrease area, then area is reduced, but noise performance deteriorates
Solution Approach 1:
By implementing periodic switching at a frequency above the noise corner frequency, the patent shapes the noise spectrum of smaller resistors. This causes the noise power to be redistributed to higher frequencies, reducing the noise power in the signal band even though the resistor area is reduced
Solution Approach 2:
The patent changes the dynamic operating parameters by switching connection nodes, which transforms the noise characteristics of smaller resistors. This parameter transformation allows compact resistors to achieve noise performance comparable to much larger resistors would provide in a static configuration
Data Source
AI summary
Systems and methods are disclosed for a signal convertor comprising a resistor or current source coupled to a positive virtual ground node and a negative virtual ground node, wherein the resistor or current source is configured to switch from the positive virtual ground node (VGP) to the negative virtual ground node (VGN), wherein the switching of the resistor or current source results in a shaping of the low frequency noise from the resistor.