Successive approximation register type adc, sigma delta adc,dual slope integrating type adc etc. However, multiramp signals are required for the proposed scheme and the first single slope adc must meet a full resolution noise specification. Dual slope adc design from power, speed and area perspectives conference paper pdf available april 2009 with 2,318 reads how we measure reads. Columnparallel dualslope integrating adc pdf version. Single slope and dual slope adc explained duration. By watching this video, you will learn the following topics. Using the dual slope ad converter function in the ht46r7xd1 rev. This paper gives an overview of the design challenges involved in.
An alternative ad conversion technique uses the singleslope ad converter. The timer is used to set a charge up time after which the same timer is used to. The advent of the dualslope converter see about integrating converters and capacitors solved the problem of integrating capacitor. A 12b twostage singleslope adc with time to digital. Therefore, the columnparallel singleslope architecture fig. The key advantage of this architecture over the singleslope is that the final. During charge phase, auxiliary clock aclk is the source clock, and therefore the sleep mode low. Since it consists of many pixels, pixel fpn can occur due to device mismatching errors. This note explains the use of offset flipping for onthefly calibration of the adc. At the start of the conversion cycle, the capacitor is totally discharged i. Pdf the dualslope conversion improvement researchgate.
This led to the development of high accuracy dualslope, tripleslope, and. 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. Adc the singleslope adc suffers all the disadvantages of the digital ramp adc, with the added drawback of calibration drift. We explain why the slightly more complicated dualslope adc is. We now consider the singleslope and the dualslope adcs. A block diagram of the circuit figure 1 includes a single primary li cell, a millivoltoutput bridge sensor, a differential amplifier, and the dualslope adc, plus correction circuitry for offset, zero, and span. It is pretty slow, but its ability to reject highfrequency noise and fixed low frequencies such as. Write the disadvantage of single slope integrator adc. The kelvin divider as we mentioned in the section on sampling theory, the output of a dac for an all 1s code is 1 lsb below the reference, so a kelvin divider dac intended for use as a. Singleslope analogtodigital conversion technique using. As we know adc is the short form of a to d converter. A fascinating question has always been how can you convert an analog voltage to an equivalent digital word.
A low power midrail dual slope analogtodigital converter for. The resulting readout structure, usually called a columnlevel adc is suitable for veryhigh resolution imagers. This analogtodigital converter adc has been at the heart of the digital volt meter. An example of sh circuit is given below the role of the capacitor is to be charged. Integrating adc a complete block diagram of a dualslope. Single slope adc architecture dual slope adc architecture. Ha0118e introduction this example shows how the internal dual slope adc function in the ht46r7xd1 device is used. Adc converter technologies may occasionally convert a spike or dip because it captures the signal repeatedly at a single point in time. 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.
Single slope and dual slope adc explained in this video, the working of dual slope and single slope integrating adc is explained. A 12b twostage singleslope adc with time to digital converter mhun shin, masayuki ikebe, junichi motohisa and eiichi sano graduate school of information science and technology, hokkaido university. 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. Adc dual slope integrator circuit a fascinating question has always been how can you convert an analog voltage to an equivalent digital word. Although singleslopeintegratorswere used in early ads and voltmeters their dependence on an integrating capacitor for stability was considered an intolerable weakness. Theuwissena,b and youngcheol chaea aelectronic instrumentation lab. Twostep single slope adc was proposed in the prior art 5, 6 in order to solve the operation speed issue of the traditional single slope adc. The counter is likewise divided into two sections, one for the msbs and one for the lsbs. An analogtodigital converter, or adc, performs the former task while a digitaltoanalog converter, or dac, performs the latter.
The dualslope conversion improvement radojle radetic1, marijana pavlovkagadejev2, nikola milivojevic3 abstract. Jagadeesh kumar, member, ieee abstracta dualslope resistancetodigital dsrdc converter that accepts the resistance of a singleelement resistivetype sensor as input and provides a direct digital output proportional. 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. Integrating adc overview aka ramp and slope adc different flavors, e. An260a 20bit1 ppm linear slopeintegrating ad converter. Figure 1 shows a conventional cmos image sensor cis with a singleslope adc ssadc. The tc500 is the base 16bit max device and requires both positive and negative power supplies. Many ad techniques utilized in the late 50s and early 60s was the singleslope. The pixel fpn conveys each output from the same light to the adc in the form of another voltage. In single slope adc, using a gray code counter is a popular scheme for time digitization, in which the. The smallest input step that can be resolved by the adc is the lsb least significant. Pdf the dualslope adc dsadc is a type of analogtodigital conversion.
Singleslope analogtodigital conversion technique using msp430 mcus figure 2. Therefore, an 8bit ad converter has 256, or 28, discrete levels for the range of analog values to be converted. 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. Soon after the discovery of the basic counting adc architectures see tutorial mt 026 it was realized that. Dualslope adc architecture a dualslope adc dsadc integrates an unknown input voltage v in for a fixed amount of time t int, then deintegrates t deint using a known reference voltage v ref for a variable amount of time see figure 2. 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. The dual slope adc is an analogtodigital converter that does its conversion using quite low bandwidth as its input. To understand the concepts of adcs, types of adc and its design procedure. Using the dual slope ad converter function in the ht46r7xd1. One form of this circuit compares a linear reference ramp to the unknown. Columnparallel single slope adc with digital correlated. A single adc cell no control or bias circuitry objectives.
A dualslope adc, on the other hand, averages together all the spikes and dips within the integration period, thus providing an output with greater noise immunity. The dualslope adc dsadc is a type of analogtodigital conversion with low input bandwidths. Pdf dual slope adc design from power, speed and area. The accurate correspondence of this adcs 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. Discussions include single, dual and multislope conversions. If the slope here means the slope of the transfer characteristic, it would be closely related to the linearity, gain and monotonous characteristic of the adc. Enter the analog to digital converter adc with the ability to convert an external signal to a processor readable value.
In this video, the working of dual slope and single slope integrating adc is explained. Columnparallel single slope adc with digital correlated multiple sampling for low noise cmos image sensors yue chena, albert j. Integrating or dual slope adc analog to digital converter engineering. Dual slope integrating adc dual slope integrating adc. Comparision of different types of adcdigital voltmeter an analogtodigital converter adc is a system that. At the end of that time it is attached to the reference voltage sw1 down. The time it takes for the integrator to trip the comparator is proportional to the unknown voltage tintvin. A dualslope adc dsadc integrates an unknown input voltage vin for a fixed amount of time tint, then deintegrates tdeint using a known reference voltage vref for a variable amount of time. Twostep single slopesar adc with error correction for. The dualslope adc architecture was truly a breakthrough in adcs for high resolution applications such as. In operation the integrator is first zeroed close sw2, then attached to the input sw1 up for a fixed time m counts of the clock frequency 1t. If high resolution is desired, then the dual slope conversion technique can be employed.
Difference between adc typescounter,flash,sar,dual slope. Improving single slope adc and an example implemented in. The single and dualslope analog to digital converters. This led to the development of high accuracy dual slope, tripleslope, and. Integrating adc a complete block diagram of a dualslope converter is shown below. Adc dual slope integrating operation input signal is integrated for a fixed time input is switched to the negative reference and the negative reference is then integrated until the integrator output is zero the time required to integrate the signal back to zero is used to embedded systems 87 compute the value of the signal. We explain why the slightly more complicated dualslope adc is generally a better choice of adc than the singleslope converter.
Dualslope adc architecture a dualslope adc dsadc integrates an unknown input voltage v in for a fixed amount of time t int, then deintegrates t deint using a known reference voltage v ref for a variable amount of time. The singleslope adc suffers the disadvantage of calibration drift. A dualslope adc dsadc integrates an unknown input voltage v. Analogtodigital converter, vin, successive approximation adc, approximation adc example, average highlow.
Both adcs make use of simple opamp circuits and control logic to do most of their work. It is pretty slow, but its ability to reject highfrequency noise and fixed low frequencies such as 50 hz or 60 hz makes it. Precise calibration of dualslope adcs application note. The singleslope adc suffers all the disadvantages of the digital ramp adc, with the added drawback of calibration drift. A columnparallel analogtodigital converter was designed for use with cmos active pixel sensors aps.
Simple dual slope ad converter dual slope ad converter output and timing dualslope adc consider this circuit. A key element of the dual slope adc is a capacitor. The tripleslope architecture retains the advantages of the dualslope, but greatly increases the. By watching this video, you will learn the following. It is then charged for a certain set time by the input voltage. One of the many interesting architectures available is the dualslope integrator. Integrating or dual slope adc analog to digital converter. Soon after the discovery of the basic counting adc architectures see tutorial mt026 it was realized that. Singleslope adc architecture the simplest form of an integrating adc uses a singleslope architecture figures 1a and 1b. The following article explains how integrating adcs work. Though the operation is quite slow, it has the ability to.
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