But the problem is i cant not come up with any ideas to make switch from v in and vref controlled by my kits which is included only basic transistors 2en3904,jfet, and some ic like 7474,7485,lm324,counter ls191,bcd display. Although single slope integratorswere used in early ads and voltmeters their dependence on an integrating capacitor for stability was considered an intolerable weakness. However, it generally has a long conversion time, so. A dualslope integration based analogtodigital convertor hasan krad department of computer science and engineering, college of engineering, qatar university, p.
So using the mshardware in dual slope more is not very useful except for debugging and initial tests. The dual slope integral analogtodigital converter is widely used in lowspeed, highprecision measurement owing to its high precision and strong resistance on. The tl507 is a lowcost singleslope analogto digital converter designed to convert analog inputvoltages between 0. You also use pdf tools to reorder, delete, or rotate pdf pages using the acrobat reader mobile app. As a minimum, each device contains the integrator, zero crossing comparator and proc essor interface logic. Figure5 depicts block diagram of dual slope integrating type adc. One of the many interesting architectures available is the dualslope integrator. The dual slope dac can use the same resistor and is this more stable in adc gain. More over i am not sure how to find the range of input voltages which can. It covers counter type adc,parallel comparator flash adc, sarsuccessive approximation register type adc,sigma delta adc, dual slope integrating type adc etc. A dual slope adc, on the other hand, averages together all the spikes and dips within the integration period, thus providing an output with greater noise immunity. Write the disadvantage of single slope integrator adc and.
With a dualslope adc you effectively get free averaging as the runup integration phase will have this effect. Resolution of dual slope adc dual slope integrating of adc resolution can be primarily determined by the time the clock runs up and down with the switch and the controllers clock frequency used at that moment. Well leave out the details of the countercontroller. The sigma delta adc, linked with a digital signal processor or microcontroller, is becoming the chief challenger to the dual slope system. In one direction of ramping, the integrator is driven by the positive analog input signal producing a negative. 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. Therefore, the columnparallel single slope architecture fig. Integrating dual slope ad converter the ald500 series is alds newest family of monolithic cmos analog processor chips that implement precision, low power, low noise integrating dual slope ad converters having a resolution of 16, 17 and 18 bits, plus sign bit and overrange bit. How to merge pdfs and combine pdf files adobe acrobat dc.
This is done twice, once with a reference source and once with a sensor. Dual slope adc design from power, speed and area perspectives conference paper pdf available april 2009 with 2,318 reads how we measure reads. It is pretty slow, but its ability to reject highfrequency noise and fixed low frequencies such as 50 hz or 60 hz makes it. H page 2 of 16 functional description the adc8 user module implements a single slope ad converter that generates an 8bit, full scale output 0 to 255 count range. 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. Hi i recently have been trying to solve this problem, which i had on an exam however i cant seem to get it right the problem is as follows. Dec 11, 2014 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. The adcr and adcd registers are, 1 cost effective device. Though the operation is quite slow, it has the ability to. Adc converter technologies may occasionally convert a spike or dip because it captures the signal repeatedly at a single point in time. 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. The dual slope adc dsadc is a type of analogtodigital conversion with low input bandwidths. The advantages of using the singleslope ad converter are increased resolution, which in the case of the 68hc705jp7 is 12 bits, and the simplicity of the design. This page covers difference between various adc types including block diagram, equation etc.
Abstract a lowpower singleslope analogtodigital converter. At the end of this interval, a known reference voltage v r of opposite polarity is applied to the. I have a project on doing simple dual slope adc using only our lab kit component. Slaae10c msp430c11x electricity meters circuit diagram for an electronic meter using msp430 mcu kwh meter ic msp430 emeter slaue10b msp430 slope example. The proposed adc consists of an analog part including an integrator and a comparator and a digital part including a controller, counter and 8bit register. About dual slope calculation is software msp lowpower. A dual slope adc ds adc integrates an unknown input voltage v. The dualslope adc dsadc is a type of analogtodigital conversion with low input bandwidths. This is a decided disadvantage because most real world signals require some smoothing. The dualslope adc dsadc is a type of analogtodigital conversion which converts an unknown input voltage u x into a digital representation through the use of an integrator, fig. However the dual slope version is usually higher noise and limited in.
It is essential that the engineering geologist be intimately familiar with all of these methods because they provide ways of determining, relatively unambiguously, whether a. The single slope adc suffers all the disadvantages. For this application note, we will build a slope converter. 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. With the advent of the advanced technology and the need for more. The ex input signal is directly coupled to the comparator input with no filtering.
Two principal advantages of the dualslope adc are its. Dual slope adcs are used in applications demanding high accuracy. During the first slope positive slope the sampling time is a fixed value and therefore the duration gives no clue about what the input voltage is. 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. Using the dual slope ad converter function in the ht46r7xd1. Numericalintegration techniques speed dualslope ad. Thus in a production environment, slight differences in each components value change the conversion result and make measurement repeatability quite difficult to attain. Why charging time is same and discharge time is different for two inputs in dual slope integrating adc. In the dualslope converter, an integrator circuit is driven positive and negative in alternating cycles to ramp down and then up, rather than being reset to 0 volts. Both adcs make use of simple opamp circuits and control logic to do most of their work. The dual slope adc is an analog todigital converter that does its conversion using quite low bandwidth as its input. Single slope 8bit adc datasheet cypress semiconductor.
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. Combine and organize your pdf from any browser with the acrobat pdf merger tool. In the dualslope converter, an integrator circuit is driven positive and negative in alternating cycles to ramp down and then up, rather than being reset to 0 volts at the end of every cycle. Dual slope adc design from power, speed and area perspectives. We now consider the singleslope and the dualslope adcs. Introduction if one electronic component is to be nominated as the workhorse inside testandmeasurement equipment, it would be the analogtodigital converter adc. 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.
The required resolution in number of bits shows minimum length of the rundown period for a fullscale input. An260a 20bit1 ppm linear slopeintegrating ad converter. Dashed lines mean control to throw a switch or convey a pulse. Explain dual slope integration type adc with the help of a.
The output is also extremely simple, just a pulse that needs to be timed which can be done with even the simplest micro controllers. Precise calibration of dualslope adcs application note. Integrating adc overview aka ramp and slope adc different flavors, e. A good circuit to look at, building a dual slope adc, could be the datron 1061 dmm, that used a dual slope like adc though with an additional slow slope. 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. An integrating adc in which the unknown signal is converted to a proportional time interval, which is then measured digitally. This is the most popular method of analog to digital conversion. We now consider the single slope and the dual slope adcs. Dual slope adc the dual, dchop dsrr dopao figure 5 dsrc dscc dual slope adc internal structure diagram 6, dual slope adc control registers using the ht46r71d1 as an example. Single slope adc architecture dual slope adc architecture. 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. A dualslope ad converter operates by charging a capacitor from the input voltage during a fixed time, then discharging it to zero. Single slope analog todigital ad conversion by stephen ledford csic product engineering austin, texas introduction the most common implementation for analog todigital ad conversion among motorola microcontrollers is the successive approximation sar method. Can anyone help me how should find the gain of the amplifier of the integrator so that i can design op amp accordingly.
Jan 26, 2018 dual slope or integrating type adc watch more videos at lecture by. 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. The advent of the dual slope converter see about integrating converters and capacitors solved the problem of integrating capacitor. Nevertheless, when considering measurement of noisy signals, as long as conversion rates of no more than 10 times per second are adequate, this is an approach that is well worth considering. It is pretty slow, but its ability to reject highfrequency noise and fixed low frequencies such as. The sampling rate is determined by the users configuration of the clock sources and is limited to a maximum of 8. Columnparallel single slope adcs for cmos image sensors martijn snoeij, albert theuwissen, kofi makinwa and johan huijsing. We are using ti msp430 for our io module cards and we have a spi adc driver for the data acquisition from field transducers. For n bit dual slop type of adc, vr 2 n n va total time for conversion of input va is expressed as follows. Using the dual slope ad converter function in the ht46r7xd1 rev. The single and dualslope analog to digital converters.
Adc dual slope integrator circuit a fascinating question has always been how can you convert an analog voltage to an equivalent digital word. 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. How analogtodigital converter adc works integrator. Dual slope adc is slow but have high accuracy and have high resistance to noise. The dualslope conversion improvement radojle radetic1, marijana pavlovkagadejev2, nikola milivojevic3 abstract. The smallest input step that can be resolved by the adc is the lsb least significant. One of the many interesting architectures available is the dual slope integrator. Delta sigma converter dual slope adc is use for converting analog to digital value. Ht46r7xd1 ha0118e ht46r7xd1 dual slope adc dual slope adc ic operation of 16 bit dual slope adc ht46r74d1 application of dual slope adc 2002 analog devices single phase energy meter abstract.
The everincreasing resolution of such imagers has had a profound impact on the analog readout electronics, and, in particular, the adc architecture. I wanted to know how to do the dual slope calculation in adc code. For a 16bit adc it would take up to 65,535 clock cycles to convert one sample. The dual slope adc dsadc is a type of analog todigital conversion with low input bandwidths. 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. Dmm basics dualslope adc posted on february 8, 20 by modemhead this is the first in a series of posts looking at how a digital multimeter actually works.
In this paper, the design optimization of a 8bit dualslope adc from power, speed and area perspectives is proposed. Slope adc analogtodigital converters can be created in a variety of ways. It uses a possible alternative way for auto zero, combined with the integrator reset. In the lecture part of this course we will discuss a variety of methods of analysis of slope stability and instability.
However, to obtain the increase in resolution, the rate of conversion is increased when compared to the sar ad. 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. This is done by integrating the unknown for a predetermined length of time. The slope converter works by timing the rate that a capacitor charges to a specified voltage. A dual slope adc ds adc integrates an unknown input voltage v hope it helps. This note explains the use of offset flipping for onthefly calibration of the adc. The dualslope integration type of ad conversion is a very popular method for digital voltmeter applications. Another common adc is the dualslope converter, which relies on integration.
Unlike a dualslope,this converter has no inherent noise rejection capability. A complete device list and corresponding data sheets or these products can be found at. An alternative ad conversion technique uses the single slope ad converter. Write the disadvantage of single slope integrator adc. Numericalintegration techniques speed dualslope ad conversion figure 1.
Difference between adc typescounter,flash,sar,dual slope. As shown in figures 410a and 410b, the voltage to be measured v x is input to an integrator, charging the capacitor for a fixed time interval t 1, which corresponds to a certain number of clock cycles. Actually, there is already adc code existing out of which i need to determine if. We explain why the slightly more complicated dualslope adc is generally a better choice of adc than the singleslope converter. There are basically 4 types of analog to digital converter adc.
Dualslope adcs are used in applications demanding high accuracy. If a filter was placed at the input substantial time lag due to settling requirements. To overcome this sensitivity to the component values, the dual slope integrating architecture is used. A dualslope integration based analogtodigital convertor. This analogtodigital converter adc has been at the heart of the digital volt meter. In this lecture, we have discussed the operation of dual slope integrating type adc. Theory of slope stability portland state university. Ss adc is presented that uses an ultralowpower reference current to achieve scription. The singleslope ad conversion utilizes several unique components. The disadvantage of a single slope integrator adc is the calibration trift dilemma and the solution to this problem is found in a design variation called the dualslope converter. Mar 22, 2014 the single slope analogtodigital converter ss adc 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. The main problem i am having is that i dont know how to solve for the required precision and the stability. Pdf working with a dualslope adc richard lao riclao.
An example of sh circuit is given below the role of the capacitor is to be charged. Integrating or dual slope adc electrical and electronics. 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. Dualslope adc architecture 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 see figure 2. 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. When compared to other types of adc techniques, the dualslope method is slow but is quite adequate for a digital voltmeter used for laboratory measurements. Usually the dual slope adc is thus a little simpler and needs less precision resistors. Pdf dual slope adc design from power, speed and area. Dual slope adc architecture a dual slope adc ds adc 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 see figure 2. 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 peak value attained contains the only clue but that is unknown to this type of adc. Thetc500a510514 family are precision analog front ends that implement dual slope ad converters having a maximum resolution of 17 bits plus sign.
This is about as good as an dual slope adc could get. The number of clock periods in the discharge time corresponds to the analog input voltage. What would a complete dual slope adc look like inside. The proposed dualslope adc can be used for applications requiring an optimum chip area, minimum power consumption and excellent performance. In the ramp techniques, the noise can cause large errors but in dual slope method the noise is averaged out by the positive and. Hello, i will have to design a dual slope adc with 11 bits. Dual slope converter an integrating adc in which the unknown. This greatly decreases the area necessary to implement the adc.
For an eightbit adc, it would take up to 255 clock cycles to convert a single sample. The tc500 is the base 16bit max device and requires both positive and negative power supplies. During the 2nd slope negative slope the input voltage is disconnected and the counter begins. We explain why the slightly more complicated dual slope adc is generally a better choice of adc than the single slope converter. I have read up about the integrator circuit and think i know how it works.
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