Linear slopeintegrating ad converter texas instruments. A complete device list and corresponding data sheets or these products can be found at. Ee247 lecture 19 university of california, berkeley. The singleslope analogtodigital converter ssadc is the most commonly used columnlevel adc for highspeed industrial, complementary metaloxide semiconductor cmosbased xray image sensors because of its small chip area the width of a pixel, its simple circuit structure, and its low power consumption. So far, weve only been able to escape the sheer volume of components in the flash converter by using a dac as part of our adc circuitry. These adcs are integrating type adc, meaning that they use the integrator for the conversion. An alternative ad conversion technique uses the singleslope ad converter. A low power midrail dual slope analogtodigital converter for.
Successive approximation register type adc, sigma delta adc,dual slope integrating type adc etc. We now consider the singleslope and the dualslope adcs. An260a 20bit1 ppm linear slopeintegrating ad converter. A singleslope adc, particularly suitable for use in a massiveparallel adc architecture in a readout circuit of a cmos imager. 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. Both adcs make use of simple opamp circuits and control logic to do most of their work.
An adcs dynamic range is the range of signal amplitudes which the adc can resolve. A 12bit highspeed columnparallel twostep singleslope. As we know adc is the short form of a to d converter. 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. Adc0831 nsingle differential input pdip package p top view figure 1. Singleslope analogtodigital conversion technique using. The paper deals with the design and construction of a fourquadrant hybrid multiplier using the quadslope technique. Columnparallel single slope adc with digital correlated multiple sampling for low noise cmos image sensors.
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. Here, an unknown input voltage is integrated and the value compared against a known. The dualslope adc dsadc is a type of analogtodigital conversion with low input bandwidths. Original signatures are on file with official student records. 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.
Counter output proportional to v in ramp generator time v ramp v ramp v in 0. It is possible to avoid using a dac if we substitute an analog ramping circuit and a digital. Analogtodigital conversion this worksheet and all related files are. The time it takes for the integrator to trip the comparator is proportional to the unknown voltage tintvin. The first stage single slope adc generates a 3bit data and 1 redundant. It is possible to avoid using a dac if we substitute an analog ramping circuit and a digital counter with precise timing. In order to obtain the binary increasing slope of the ramp signals, iint is seeded by a 2bit current dac. Adcs, integrating, multislope, multislope, lcd drivers, led. Recent listings manufacturer directory get instant insight into any electronic component. Timebased analog to digital converters by shahrzad naraghi a dissertation submitted in partial fulfillment of the requirements for the degree of doctor of philosophy electrical engineering. An863 a comparator based slope adc microchip technology. The singleslope adc suffers all the disadvantages of the digital ramp adc, with the added drawback of calibration drift. Integrating adc overview aka ramp and slope adc different flavors, e.
For discharge phase, subsystem master clock smclk is used derived from the dco because of the higher frequency and greater slope adc accuracy. Us7924207b2 single slope analogtodigital converter. The single and dualslope analog to digital converters. Columnparallel single slope adc with digital correlated. Figure 1a shows the block diagram of a cis with a column parallel adc. The proposed adc employs a single ramp voltage and multiple reference voltages, and the conversion is divided into coarse phase and fine phase to.
Integrating adcs ece614 advanced analog ic design presented by antonio oblea may 7, 2008. Table 1 expresses the specifications of topend dvms in a typical adc format. Columnparallel dualslope integrating adc pdf version. To convert analog signals to digital ones is needed to keep. During charge phase, auxiliary clock aclk is the source clock, and therefore the sleep mode low power mode 3 lpm3 is used. Although the proliferation of high resolution sigmadelta adcs has made integrating architectures somewhat less popular, they are still used.
Analog to digital converter adc is an electronic integrated circuit used to convert the analog signals such as voltages to digital or binary form consisting of 1s and 0s. If the signal is too large, it overranges the adc input. Here, an unknown input voltage is integrated and the value compared against a known reference value. Though the operation is quite slow, it has the ability to. Dynamic range is important in communication applications, where signal strengths vary dramatically. Columnparallel singleslope adcs for cmos image sensors martijn snoeij, albert theuwissen, kofi makinwa and johan huijsing. Improving single slope adc and an example implemented in.
Therefore, the columnparallel singleslope architecture fig. A columnparallel analogtodigital converter was designed for use with cmos active pixel sensors aps. In single slope adc, using a gray code counter is a popular scheme for time digitization, in which the. The dual slope adc is an analogtodigital converter that does its conversion using quite low bandwidth as its input. The tc500 is the base 16bit max device and requires both positive and negative power supplies. Singleslope adc architecture the simplest form of an integrating adc uses a singleslope architecture figures 1a and 1b. The accurate correspondence of this adcs output with its input is dependent on the voltage slope of the integrator being matched to the. Then a known reference voltage of opposite polarity is applied to the integrator and is allowed to ramp until the integrator output returns to zero the rundown period.
It is pretty slow, but its ability to reject highfrequency noise and fixed low frequencies such as. Since it consists of many pixels, pixel fpn can occur due to device mismatching errors. A characteristic to measure with a slope adc is resistance. Analogtodigital converter design guide highperformance, standalone ad converters for a variety of embedded systems applications design ideas in this guide are based on many of microchips adc products. 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. A dualslope adc dsadc integrates an unknown input voltage v. The pixel fpn conveys each output from the same light to the adc in the form of another voltage. Three standards that define specification terms for adcs and dacs are. A single adc cell no control or bias circuitry objectives. Temperature measurement, or control, is one of the more common applications of microprocessor systems. Integrating analogtodigital converters adcs provide high. Figure 2 shows the diagram of the accelerated continuoustime differential ramp generator. A plurality of ramp signals are generated which define nonoverlapping subranges of the full input range. Explain the operating principle of a dualslope adc.
Maxim design support technical documents tutorials ad and da. Successive approximation analog to digital converter adc description of operation a successive approximation adc works by using a digital to analog converter dac and a comparator to perform a binary search to. This paper presents an 11bit twostep single slopesuccessive approximation register sar adc scheme for cmos image sensor applications. By using a thermistor, temperature can be directly converted to a resistance. Processor causes the voltage at the input to the opamp circuit to go from 0 v to vref. Measuring a thermistor is a good way to demonstrate the functions of a slope adc. In this video, the working of dual slope and single slope integrating adc is explained. Analogue to digital and digital to analogue converters adcs and. Comparision of different types of adcdigital voltmeter an analogtodigital converter adc is a system that.
A prototype imager using the mrss adc architecture was realized in a 0. But once the slope of input signal changes very fast, the clock frequency or conversion rate is increased to track the input signal with high fidelity. The quadslope multiplier is a multiplying analoguetodigital converter based. September 47, 2011, athens, greece columnparallel single slope adc with digital correlated multiple sampling for low noise cmos image sensors yue chen a, albert j. This paper gives an overview of the development of columnparallel adcs that enable the highspeed, powerefficient readout of highresolution cmos imagers. A tracking adc with transientdriven self clocking for. Research article twostep single slopesar adc with error. The dualslope converter, and variants on it, have been refined to a point where 16 and 17bit resolution.
Slope integrating adc chapter digitalanalog conversion pdf version. When the ramp potential crosses the unknown input voltage a comparator changes state. Difference between adc typescounter,flash,sar,dual slope. Adc0838n8channelmux soicpdip package dw or nfh top view com internally connected to gnd. Measurements demonstrate that the conversion speed of an mrss adc is 3. A 12bit highspeed columnparallel twostep singleslope ss analogtodigital converter adc for cmos image sensors is proposed.
Slope integrating adc slope integrating adc the singleslope adc suffers all the disadvantages of the digital ramp adc, with the added drawback of calibration drift. This choice is nevertheless unusual because of singleslopes reputation for long conversion time, normally taking 2nbits time steps, where n. One form of this circuit compares a linear reference ramp to the unknown voltage input see about integrating converters and capacitors. Therefore, an 8bit ad converter has 256, or 28, discrete levels for the range of analog values to be converted. The basic function of an adc is to convert a voltage applied to its input into a number with a. Twostep single slopesar adc with error correction for. The dual slope converter is the most commonly used of the charge balance type. Understanding integrating adcs tutorial maxim integrated. As a minimum, each device contains the integrator, zero crossing comparator and proc essor interface logic. 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. The singleslope adc suffers all the disadvantages of the digital ramp adc. 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. In this work a dll based single slope adc is proposed which can increase the readout.
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