Dual-Voltage Comparator Circuit for Fast Low-Power Pixel ADCs
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Solution Overview
Problem
In solid-state imaging apparatuses, there is a challenge in accommodating a comparator within a limited area, leading to reduced decision speed or increased power consumption when attempting to enhance performance.
Innovation Solution
A comparator design with a differential input circuit operating at a first power source voltage, a positive feedback circuit operating at a second, lower power source voltage to speed up transition, and a voltage converting circuit to adapt the output signal to the second power source voltage, with the differential input circuit's source voltage being lower than 0 V.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the comparator is designed with higher performance (faster decision speed), then the decision speed is improved, but the power consumption increases
Solution Approach 1:
The comparator is divided into two functional segments: a differential input circuit operating at a higher first power source voltage for accurate comparison, and a positive feedback circuit operating at a lower second power source voltage for speed enhancement. This segmentation allows each part to operate at optimized voltage levels, achieving fast decision speed through the feedback circuit while controlling overall power consumption through the lower voltage operation of the feedback portion.
Solution Approach 2:
The patent changes the voltage parameter by introducing dual power source voltages with different levels. The differential input circuit operates at the first power source voltage while the positive feedback circuit operates at the second power source voltage which is lower than the first. This parameter change enables the feedback circuit to provide rapid transition (improving decision speed) while consuming less power compared to operating the entire comparator at high voltage.
2Area of stationary object
If the comparator is designed to operate in limited area, then the area efficiency is improved, but the performance (decision speed or power consumption) deteriorates
Solution Approach 1:
By changing the voltage parameter to use dual power source levels, the patent achieves enhanced decision speed within the same limited area. The positive feedback circuit operating at the lower second power source voltage provides rapid transition, improving decision speed without requiring additional area for extra circuit components.
3Area of stationary object
If the comparator is designed to operate in limited area, then the area efficiency is improved, but the power consumption increases
Solution Approach 1:
The comparator is segmented into two voltage domains: the differential input circuit at the first power source voltage and the positive feedback circuit at the lower second power source voltage. This segmentation allows the feedback circuit to operate efficiently at lower voltage, reducing overall power consumption while maintaining compact area implementation.
Solution Approach 2:
The patent changes the voltage parameter by implementing dual power source operation, where the positive feedback circuit operates at a lower voltage level. This parameter change reduces power consumption in the feedback portion while maintaining fast transition, achieving efficient operation within limited area without excessive power consumption.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design reduces power consumption while enhancing the decision speed of the comparator, achieving efficient operation in constrained areas.
Implementation Method 1
a positive feedback circuit operating at a second power source voltage lower than the first power source voltage, and speeding up a transition speed when a comparison result signal representing a result of comparison in voltage between the input signal and the reference signal is inverted on the basis of an output signal from the differential input circuit
Data Source
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AI summary
The present disclosure relates to a comparator, an AD converter, a solid-state imaging apparatus, an electronic apparatus, and a method of controlling a comparator each of which enables power consumption to be reduced while a decision speed of the comparator is enhanced. A comparator, including: a differential input circuit operating at a first power source voltage, and outputting a signal when a voltage of an input signal is higher than a voltage of a reference signal; a positive feedback circuit operating at a second power source voltage lower than the first power source voltage, and speeding up a transition speed when a comparison result signal representing a result of comparison in voltage between the input signal and the reference signal is inverted on the basis of an output signal from the differential input circuit; and a voltage converting circuit converting the output signal from the differential input circuit into a signal corresponding to the second power source voltage, in which a source voltage of the differential input circuit is a voltage lower than 0 V. The present disclosure, for example, can be applied to an ADC or the like which is arranged for each pixel of a solid-state imaging apparatus.