Pdf dual slope adc design from power, speed and area. A singleslope 80mss adc using twostep timetodigital. Counter output proportional to v in ramp generator time v. A dualslope adc dsadc integrates an unknown input voltage vin for a fixed. Applying the tdc that uses multiphaseclock signal reduced the.
One method of addressing the digital ramp adcs shortcomings. Singleslope adc architecture the simplest form of an integrating adc uses a singleslope architecture figures 1a and 1b. To achieve more vivid image, the dimensions of infrared focal plane array need to be enlarged. The proposed algorithm uses single slope ramp adc timing on a columnparallel cmos image sensor. An 80 mss analogtodigital converter adc based on singleslope conversion is presented which utilizes a recently developed gated ring oscillator gro timetodigital converter tdc to achieve an enob of 6. Pdf twostep single slopesar adc with error correction for. However, ssadc has a very low conversion speed, especially when high resolution is required. A 12bit highspeed columnparallel twostep singleslope. The singleslope adc suffers all the disadvantages of the digital ramp adc. The pixel fpn conveys each output from the same light to the adc in the form of another voltage. This adc circuit behaves very much like the digital ramp adc, except that the comparator reference voltage is a smooth sawtooth waveform rather than a stairstep. Single slope analogtodigital ad conversion by stephen ledford csic product engineering austin, texas introduction the most common implementation for analogtodigital ad conversion among motorola microcontrollers is the successive approximation sar method.
Both adcs make use of simple opamp circuits and control logic to do most of their work. Dualslope converter timing diagram the advantage of a dualslope adc is that it is not dependent on the correction factor for the rc product. Conventional twostep adc for cmos image sensor requires full resolution noise performance in the first stage single slope adc, leading to high power consumption and large chip area. Nprp 50802028 from qatar national research fund a member of qatar foundation. Assuming that the format of 12bit output is b11b10b0, then the 8 bits. In single slope adc, using a gray code counter is a popular scheme for time digitization, in which the. An alternative to a single adc is to move the task of analogto digital conversion into the readout column fig. Msp430 mcus without an integrated adc module, resistive elements still can be. Pdf design 8 bit analog unit adc integrating type single. We explain why the slightly more complicated dualslope adc is generally a better choice of adc than the singleslope converter. The proposed adc employs a single ramp voltage and multiple reference voltages, and the conversion is divided into coarse phase and fine phase to improve the conversion rate.
We propose a singleslop adc with a time to digital converter tdc that uses a multiphase clock. Research article twostep single slopesar adc with error. Single slope adc if you are looking for strong and loyal friendship, interesting interlocutors or for partner of all your life then you at suitable service with comfortable and versatile dating search. Figure 1 shows a conventional cmos image sensor cis with a single slope adc ss adc. The effect of this circuit is to produce a dac output that ramps up to whatever. In its basic implementation, the dual slope converter, the unknown input voltage is applied to the input of the integrator and allowed to ramp for a fixed time period the runup period. But, in some cases it is necessary to measure both positive and negative voltages. The implementation presented demonstrates the slope ad conversion resistance measurement using the onchip comparator and timer of the msp430 mcus. Hence the high speed analog to digital converter adc integrated onchip needs to obtain the digital infrared imaging signal. For the singleslope ad converter, the analog value is represented as an elapsed time and thus a 12bit resolution has 4096, or 212, discrete counts for the full range of voltage input. The proposed scheme solves the multiphase clock period matching problem in flash tdcinterpolation of ss adcs without the use of a delaylockedloop. The adc10 user module implements a single slope ad converter that generates up to a 12bit, full scale output 0 to 4095 count range.
In a single slope adc, there is a tradeoff between. This work presents a hybrid columnparallel timetodigitalconverter interpolated tdc single slope ss adc with a digital delay element feedback. Places the digitalramp adc at a disadvantage to other counter strategies. The ad converter is composed of both 5bit coarse adc and a 6bit fine adc, and the conversion speed is 10 times. Dual range adc block diagram figure 5 shows the block diagram of a dual range adc.
How analogtodigital converter adc works integrator. Write the disadvantage of single slope integrator adc and. In single slope adc, using a gray code counter is a popular scheme for time digitization, in. A dualslope adc dsadc integrates an unknown input voltage v. Twostep single slopesar adc with error correction for. Singleslope analogtodigital conversion technique using. In singleslope integrating adc on opamp based circuit, called an integrator to generate a saw tooth wave form is used, instead of the use of a dac with a ramped output. Further resolution is achieved by averaging multiple samples. Due to the advantages of the uncooled infrared focal plane array uifpa, it is widely used in various fields.
The single slope adc suffers all the disadvantages of the digital ramp adc. Columnparallel single slope adc with digital correlated. We explain why the slightly more complicated dualslope adc is. Singleslope analogtodigital conversion technique using msp430. There are a few ways of designing analogtodigital converters using an integrator. Msp430 mcus without an integrated adc module, resistive elements still can be precisely measured with the onchip comparator and timer using single slope analogtodigital ad conversion technique. Improving single slope adc and an example implemented in. Lets take a look at two of them, singleslope adc and deltasigma adc. Features and overview 8bit resolution sample rates up to 8. Theuwissen a,b and youngcheol chae a a electronic instrumentation lab. This choice is nevertheless unusual because of single slope s reputation for long conversion time, normally taking 2nbits time steps, where n bits is the adc resolution. Counter output proportional to v in ramp generator time v ramp v ramp v in 0. Here, an unknown input voltage is integrated and the value compared against a known reference value.
Twostep single slopesar adc with error correction for cmos. Dual slope converter timing diagram the advantage of a dual slope adc is that it is not dependent on the correction factor for the rc product. Columnparallel dual slope integrating adc pdf version. In single slope adc, using a gray code counter is a popular scheme for time digitization, in which the comparator. Singleslope adcs have been used as column parallel adcs for cmos image sensors. The analog unit is designed precisely to meet characteristics of the adc. The main component of analog to digital converter adc single slope type is an analog unit.
Design of a cmos image sensor based on a 10bit twostep. A single adc cell no control or bias circuitry objectives. This work presents a hybrid columnparallel timetodigitalconverter interpolated tdc singleslope ss adc with a digital delay element feedback. The is the basic idea behind the socalled singleslope, or integrating adc. The single slope adc ss adc is commonly employed for the columnparallel adc of cis, because ss adc has small chip area, low noise, and low power consumption 79. Ramp type adc pdf voltagetofrequency, staircase ramp or single slope. An alternative ad conversion technique uses the singleslope ad converter. In dual slope type adc, the integrator generates two different ramps, one with the known analog input voltage va and another with a known reference voltage vref. Dexue zhang, rami yassine, loc truong, jeff rysinski, daniel van blerkom, barmak mansoorian, forza silicon corporation subject.
Therefore, an 8bit ad converter has 256, or 28, discrete levels for the range of analog values to be converted. Slope integrating adc slope integrating adc the single slope adc suffers all the disadvantages of the digital ramp adc, with the added drawback of calibration drift. Not only is the flash converter the simplest in terms of operational theory, but it is the most efficient of the adc technologies in terms of speed, being limited only in comparator and gate propagation delays. The is the basic idea behind the socalled single slope, or integrating adc. Assuming that the format of 12bit output is b11b10b0, then the 8. The basic working principle of slope ad resistance measurement is the charging and discharging of a known value capacitor cm through the. High frame rate vga cmos image sensor using three step. We explain why the slightly more complicated dual slope adc is generally a better choice of adc than the single slope converter. The tc500 is the base 16bit max device and requires both positive and negative power supplies. A dual slope adc ds adc integrates an unknown input voltage v. We now consider the single slope and the dual slope adcs.
Therefore, the columnparallel singleslope architecture fig. Msp430 mcus without an integrated adc module, resistive elements still can be precisely measured with the onchip comparator and timer using singleslope analogtodigital ad conversion technique. Single slope adc architecture the simplest form of an integrating adc uses a single slope architecture figures 1a and 1b. Abstract single slope adc is a common building block in many asci or fpga based frontend systems due to its simplicity, small silicon footprint, low noise interference and low power consumption. Difference between adc typescounter,flash,sar,dual slope. Single slope adc is a common building block in many asci or fpga based frontend systems due to its simplicity, small silicon footprint, low noise interference and low power consumption. One form of this circuit compares a linear reference ramp to the unknown voltage input see about integrating converters and capacitors. Column parallel singleslope adc with time to digital. This paper presents an areaefficient and lowpower 12b successive approximation register single slope analogtodigital converter sarss adc for cmos image sensor cis applications.
Dual slope adc design from power, speed and area perspectives conference paper pdf available april 2009 with 2,318 reads how we measure reads. In its basic implementation, the dualslope converter, the unknown input voltage is applied to the input of the integrator and allowed to ramp for a fixed time period the runup period. As a result, ssadc is difficult to employ for high resolution. Singleslope analogtodigital ad conversion by stephen ledford csic product engineering austin, texas introduction the most common implementation for analogtodigital ad conversion among motorola microcontrollers is the successive approximation sar method. A 12bit highspeed columnparallel twostep singleslope ss analogtodigital converter adc for cmos image sensors is proposed. The time it takes for the integrator to trip the comparator is proportional to the unknown voltage tintvin. Investigations of timeinterpolated singleslope analogto. The simplest form of an integrating adc uses a singleslope architecture. Measurements demonstrate that the conversion speed of an mrss adc is 3. This requires an external adc with this particular capability. Paper single slope adc analog to digital converter digital. An example of sh circuit is given below the role of the capacitor is to be charged. However, ss adc has a very low conversion speed, especially when high resolution is required.
The effect of this circuit is to produce a dac output that ramps up to whatever level the analog input signal is at, output the binary number corresponding to. The singleslope adc suffers all the disadvantages of the digital ramp adc, with the added drawback of calibration drift. We now consider the singleslope and the dualslope adcs. The time it takes for the integrator to trip the comparator is proportional to the unknown voltage t int v in. The resulting readout structure, usually called a columnlevel adc is suitable for veryhigh resolution imagers. Write the disadvantage of single slope integrator adc and how does dual slope integrator adc overcome this problem. An integrating adc is a type of analogtodigital converter that converts an unknown input voltage into a digital representation through the use of an integrator. Although capable of generating a 12bit output, it has only 10 effective bits of resolution. A dual slope adc ds adc integrates an unknown input voltage v hope it helps. The simplest form of an integrating adc uses a singleslope. High frame rate vga cmos image sensor using three step single. One of the many ad techniques utilized in the late 50s and early 60s was the single slope integrating converter. When the ramp potential crosses the unknown input voltage a comparator changes state.
Maxim design support technical documents tutorials ad and da. A pipelined 5msamples 9bit analogtodigital converter ieee jssc, vol. When the tdc with resolution of n bits is adapted to the adc, the conversion time is reduced by a factor of 2 n. Analogtodigital conversion this worksheet and all related files are. Ee247 lecture 19 university of california, berkeley. One of the many ad techniques utilized in the late 50s and early 60s was the singleslopeintegrating converter. A prototype imager using the mrss adc architecture was realized in a 0. A high resolution single slope adc with low operation. This paper proposes a new twostep ss adc using a single ramp. The conclusion of the study showed the efficiency of the dual slope adc as compared to other adcs, most especially the single slope adc keywords dual slope, adc, 8 bit, counter, cascaded 4 bit. Figure 1 shows a conventional cmos image sensor cis with a singleslope adc ssadc. To convert analog signals to digital ones is needed to keep. Figure 1a shows the block diagram of a cis with a column parallel adc.
As a minimum, each device contains the integrator, zero crossing comparator and proc essor interface logic. An input circuit called a sample and hold performs this taskin most cases by. Single slope adc if you are looking for that special someone, then our online dating site is the place to be. Instead of using a dac with a ramped output, we use an opamp circuit called an integrator to generate a sawtooth waveform which is then compared against the analog input by a comparator. Single slope adc with onchip accelerated continuoustime.
Single slope adc with onchip accelerated continuoustime differential ramp generator for low noise columnparallel cmos image sensor author. Columnparallel single slope adc with digital correlated multiple sampling for low noise cmos image sensors. Ee247 lecture 18 university of california, berkeley. Pdf a 12bit highspeed columnparallel twostep singleslope. Unfortunately, it is the most component intensive for any given number of output bits. Therefore, the columnparallel single slope architecture fig. The accurate correspondence of this adc s output with its input is dependent on the voltage slope of the integrator being matched to the counting rate of the counter the clock frequency. As a result, ss adc is difficult to employ for high resolution.
This page covers difference between various adc types including block diagram, equation etc. Improving single slope adc and an example implemented in fpga. The single and dualslope analog to digital converters. We choose a single slope adc as a candidate for interleaving because of its simplicity, linearity, lowpower operation, small area, and small input capacitance. To get started, download project files and a code example. It has been optimized for lowest code size, fitting in a lowcost 0. Since it consists of many pixels, pixel fpn can occur due to device mismatching errors. Explain the operating principle of a dualslope adc. It covers counter type adc,parallel comparator flash adc, sarsuccessive approximation register type adc,sigma delta adc,dual slope integrating type adc etc.
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