Single-Ended to Differential Circuit for Full-Resolution ADC Conversion
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Solution Overview
Problem
Existing single-ended to differential conversion methods for input-feedforward delta-sigma modulators result in a loss of resolution due to the direct connection of single-ended inputs to differential converters, and there is a need for an embedded solution within ADCs that addresses power consumption and timing constraints.
Innovation Solution
A novel single-ended to differential circuit that samples input and reference voltages using capacitors or inductors and employs a switching circuit with a control signal to determine output voltages, allowing for embedded conversion within ADCs and relaxing timing constraints by decoupling the control signal's stability from the sampling phase.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single-ended input is directly connected to one differential input of a differential converter, then the circuit complexity is reduced, but the resolution is lost by 1-bit (6 dB)
Solution Approach 1:
The single-ended to differential conversion is segmented into multiple phases (first phase for sampling input voltage, second phase for sampling reference voltages, third phase for differential conversion). This segmentation allows the circuit to maintain high resolution by properly handling both the single-ended input and differential reference voltages through separate sampling operations, avoiding the resolution loss that would occur with direct connection.
Solution Approach 2:
The input voltage and reference voltages are sampled in advance during the first and second phases before the actual differential conversion in the third phase. This preliminary sampling action allows the circuit to prepare the necessary voltage values with proper timing, ensuring that the differential conversion maintains full resolution without requiring complex real-time processing.
2Measurement precision
If a dedicated single-ended to differential conversion circuit is used in the front end, then the resolution is maintained, but the power consumption increases
Solution Approach 1:
The single-ended to differential conversion circuit is merged with the delta-sigma modulator by sharing the same integrator stages and memory elements. The conversion operation is combined with the existing modulator phases, allowing the circuit to maintain full resolution while utilizing the power already allocated for the modulator's normal operation, thereby avoiding additional power consumption.
Solution Approach 2:
The integrator stages and memory elements serve multiple functions: they perform both the single-ended to differential conversion and the normal delta-sigma modulation integration. This multi-functionality allows the circuit to maintain resolution without requiring dedicated power-consuming conversion circuitry, as the same components perform both conversion and modulation tasks.
3Device complexity
If the control signal stability is coupled with the sampling phase, then the timing is simplified, but the timing constraints are too strict for input-feedforward delta-sigma modulators
Solution Approach 1:
The timing operation is segmented into distinct phases: the first phase samples the input voltage, the second phase samples the reference voltages, and the third phase performs the differential conversion. This segmentation decouples the control signal stability requirement from the sampling phase, allowing the control signal to be stable at the beginning of the third phase rather than during the sampling phases, thereby providing timing constraint flexibility for input-feedforward modulators.
Solution Approach 2:
The sampling of input and reference voltages is performed in advance during the first and second phases, preparing the necessary values before the differential conversion phase. This preliminary action allows the control signal to stabilize later, at the beginning of the third phase, without compromising the sampling accuracy, thus relaxing the timing constraints while maintaining proper operation.
Data Source
AI summary
A single-ended to differential circuit is presented. The circuit may be a single-ended to differential integrator or a single-ended to differential amplifier. The circuit determines a first output and a second output voltage based on an input voltage, first and second reference voltages. The circuit has a first, a second and a third input memory element. The circuit in a first phase, samples a voltage indicative of the input voltage on the first input memory element. The circuit in the first phase, samples a voltage indicative of the first reference voltage on the second input memory element. The circuit in the first phase, samples a voltage indicative of the second reference voltage on the third input memory element. The circuit, in a second phase, determines the first and second output voltage based on the sampled voltages on the first, second, and third input memory elements.