TDC-based high-speed column level ADC for imaging sensor

Abstract

The invention belongs to the field of analog-digital conversion circuits. For the CIS with a large pixel array or high scanning speed, in order to reducing conversion time of a column level single-slope ADC under the condition that the area and power consumption are not greatly increased, the adopted technical scheme is that a TDC-based high-speed column level ADC for an imaging sensor is provided. The TDC-based high-speed column level ADC is composed of a phase-locked loop circuit PLL, a gating ring oscillator GRO, two phase inverters, an AND gate circuit, two D triggers, a counter, a delayed phase-locked loop circuit DLL, a vernier delay line VDL and a code value arithmetic unit. The TDC-based high-speed column level ADC for the imaging sensor is mainly applied to analog-digital conversion devices.

Description

technical field [0001] The invention belongs to the electrical field and relates to an analog-to-digital conversion, in particular to the realization of a column-level ADC applied in an image sensor. Specifically, TDC-based high-speed column-level ADCs for image sensors technical background [0002] With the rapid development of digital technology and semiconductor manufacturing technology, CMOS image sensor (CIS) has become the object of current and future market attention. At present, there are three main architectures of analog-to-digital converters (ADCs) used in CMOS image sensors: chip level, pixel level, and column-parallel level. On-chip ADCs use one ADC for the entire pixel array, so the ADC must be very fast to achieve a high frame rate. Pixel-level ADCs place an ADC in each pixel to achieve extremely high frame rates, but this comes at the expense of silicon area and power consumption. The array-level ADC is converted by an ADC for each column, so as to achieve...

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Problems solved by technology

[0005] (2) Mismatch between columns in the column-level A / D converter will introduce column-level fixed pattern noise

It can be seen that with the improvement of conversion accuracy, the conversion time increases exponentially, which greatly limits the readout rate of CMOS image sensors.

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