Pixel A/D Comparator Circuit With Dual-Voltage Fast Determination
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Solution Overview
Problem
In solid-state imaging apparatuses, the limited area for housing circuits within each pixel makes it difficult to manufacture comparators that meet requirements, often resulting in reduced determination speed.
Innovation Solution
A solid-state imaging apparatus with an A/D converter that includes a differential input circuit, a positive feedback circuit operating on a lower power supply voltage, and a voltage conversion circuit to accelerate comparison result signal transitions, along with multiple time code transfer sections using shift registers to enhance determination speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the comparator circuit is designed with sufficient size to maintain high determination speed, then the determination speed is improved, but the circuit area increases beyond the limited pixel area
Solution Approach 1:
The comparator circuit is divided into two functional segments: a differential input circuit operating at high voltage (first power supply voltage) for accurate signal comparison, and a positive feedback circuit operating at low voltage (second power supply voltage) for accelerating output transition. This segmentation allows each part to be optimized independently, achieving high speed without proportionally increasing total area.
Solution Approach 2:
The patent changes the voltage parameter across different circuit stages. The differential input circuit operates at a first power supply voltage for accurate comparison, while the positive feedback circuit operates at a lower second power supply voltage. This parameter change enables the feedback circuit to provide strong driving capability for fast transition while consuming less area compared to a full-high-voltage design.
2Use of energy by stationary object
If the power supply voltage is reduced to save power and reduce area, then energy consumption and area are reduced, but the determination speed decreases
Solution Approach 1:
The power consumption is segmented across two voltage levels. The differential input circuit consumes higher power at first power supply voltage to maintain accurate comparison capability, while the positive feedback circuit consumes lower power at second power supply voltage. The low-voltage feedback circuit provides sufficient driving strength for fast transition without the full power cost of a high-voltage design.
Solution Approach 2:
By changing the power supply voltage parameter from first voltage to second voltage between the differential input circuit and the positive feedback circuit, the patent achieves a balance between power consumption and speed. The voltage conversion enables the feedback circuit to operate efficiently at lower voltage while still providing adequate driving capability for fast determination.
Data Source
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AI summary
The present disclosure relates to a solid-state imaging apparatus, a method for driving the solid-state imaging apparatus, and electronic equipment for improving the determination speed of comparators and allowing the comparators to operate faster. A differential input circuit operates on a first power supply voltage and outputs a signal when a voltage of a pixel signal is higher than a voltage of a reference signal. A voltage conversion circuit converts the output signal from the differential input circuit into a signal corresponding to a second power supply voltage. A positive feedback circuit accelerates a transition rate at which a comparison result signal indicative of the result of a comparison in voltage between the pixel signal and the reference signal is inverted, on the basis of the output signal of the differential input circuit converted by the voltage conversion circuit. Multiple time code transfer sections each include a shift register that transfer a time code. The present disclosure can be applied, for example, to a solid-state imaging apparatus including A/D converters disposed in pixels.