The key advantage of this architecture over the singleslope is that the final. Dual slope adc architecture a dual slope adc ds adc 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. By watching this video, you will learn the following topics. It has the added advantage of maintaining accuracy in a noisy environment. Us7924207b2 single slope analogtodigital converter. Dualslope integrating adc dual slope integrating adc. 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. However, it generally has a long conversion time, so we propose an innovative.
Precise calibration of dualslope adcs application note maxim. A dual slope integration based analogtodigital convertor hasan krad department of computer science and engineering, college of engineering, qatar university, p. An integrating adc is a type of analog todigital converter that converts an unknown input voltage into a digital representation through the use of an integrator. A key element of the dual slope adc is a capacitor. Simple dual slope ad converter dual slope ad converter output and timing dual slope adc consider this circuit. A dualslope integration based analogtodigital convertor hasan krad department of computer science and engineering, college of engineering, qatar university, p. 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 time it takes for the integrator to trip the comparator is proportional to the unknown voltage t int v in. One form of this circuit compares a linear reference ramp to the unknown voltage input see about integrating converters and capacitors. As mentioned previously, the single slope ad has many similarities to the sar ad. The block diagram of a dual slope adc is shown in the following figure. A dualslope adc dsadc integrates an unknown input voltage v.
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. Case 3 a businessman is talking to his sales office in rome. The simplest form of an integrating adc uses a singleslope architecture figures 1a and 1b. Singleslope analogtodigital conversion technique using. Article pdf available in ieee transactions on instrumentation and measurement. Explain dual slope integration type adc with the help of a. 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. A block diagram of the circuit figure 1 includes a single primary li cell, a millivoltoutput bridge sensor, a differential amplifier, and the dual slope adc, plus correction circuitry for offset, zero, and span.
Singleslope ad example the main components of the singleslope system are the comparator, the constant current source for the external capacitor, and the free. Precise calibration of dualslope adcs application note. A columnparallel dual gain single slope adc comprises an input for receiving a signal vin, a sample and hold stage which receives vin and outputs sampled signal vin,samp, a comparator, a counter, and a ramp generator which generates highgain hg and lowgain lg ramps, with the ratio of the lg ramp slope to the hg ramp slope being greater than 1. Write the disadvantage of single slope integrator adc and.
For the adcs discussed to this point, a timevarying signal was sampled or the adc operated so rapidly that, for practical purposes, the signal did not change during a single conversion. Characteristics of different slope converters an2615 1237 6. The design goals included simplicity, small size, moderate speed 10khz, current input. Adc converter technologies may occasionally convert a spike or dip because it captures the signal repeatedly at a single point in time. We now consider the singleslope and the dualslope adcs. Difference between adc typescounter,flash,sar,dual slope. Columnparallel dual slope integrating adc pdf version. N digital thermometer decoder circuit converts the compared. This note explains the use of offset flipping for onthefly calibration of the adc. A columnparallel analogtodigital converter was designed for use with cmos active pixel sensors aps. At the end of this interval, a known reference voltage v r of opposite polarity is applied to the integrator.
Us10205463b1 dualgain singleslope adc with digital cds. 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. Although singleslopeintegrators were used in early ads and voltmeters their. At the end of that time it is attached to the reference voltage sw1 down. Ee247 lecture 19 university of california, berkeley. 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. Figure5 depicts block diagram of dual slope integrating type adc. Therefore, the columnparallel single slope architecture fig. A dual slope adc, on the other hand, averages together all the spikes and dips within the. The key advantage of this architecture over the singleslope. We explain why the slightly more complicated dual slope adc is generally a better choice of adc than the single slope converter.
Integrating adc overview aka ramp and slope adc different flavors, e. Singleslope adc architecture the simplest form of an integrating adc uses a singleslope architecture. Hence it is called a s dual slope a to d converter. The dualslope converter, and variants on it, have been refined to a point where. The dualslopeconverter features high accuracy, since its performance is independenl of the exact values of rand e. The tc514 adds both a negative power supply converter and a 4input. Both adcs make use of simple opamp circuits and control logic to do most of their work. Single slope ad example the main components of the single slope system are the comparator, the constant current source for the external capacitor, and the free. One of the many ad techniques utilized in the late 50s and early 60s was the single slope integrating converter. To understand the concepts of adcs, types of adc and its. Pdf the dualslope adc dsadc is a type of analogtodigital. By watching this video, you will learn the following. An example of sh circuit is given below the role of the capacitor is to be charged. The dualslope integration type of ad conversion is a very popular method for digital voltmeter applications.
If the analog signal is noisy contains significant levels of spurious voltage spikesdips, one of the other adc converter technologies may occasionally convert a spike or dip because it captures the signal repeatedly at a single point in time. These similarities can be seen in the conceptual diagram of a singleslope system infigure 2. 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 circuit shown to the right is an example of a multi slope rundown. The single and dualslope analog to digital converters. Single slope and dual slope adc explained duration. When compared to other types of adc techniques, the dual slope method is slow but is quite adequate for a digital voltmeter used for laboratory measurements. An260a 20bit1 ppm linear slopeintegrating ad converter. Singleslope 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. 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 key advantage of this architecture over the singleslope is. A separate ramp generator is preferably provided to generate each ramp signal.
Single slope adc architecture dual slope adc architecture. 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. During autozero, the errors in the analog components buffer offset voltages, etc. Jun 01, 2019 in this video, the working of dual slope and single slope integrating adc is explained. For n bit dual slop type of adc, vr 2 n n va total time for conversion of input va is expressed as follows. With the advent of the advanced technology and the need for more. These similarities can be seen in the conceptual diagram of a single slope system infigure 2.
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. It is then charged for a certain set time by the input voltage. A dual slope adc ds adc integrates an unknown input voltage v. The dual slope integration type of ad conversion is a very popular method for digital voltmeter applications. All singleslope converters are basically voltagetotime or currenttotime converters.
We explain why the slightly more complicated dualslope adc is. Dualslope converter timing diagram the advantage of a dualslope adc is that it is not dependent on the correction factor for the rc product. The key advantage of this architecture over the single slope is. The single slope adc suffers the disadvantage of calibration drift. 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. In this video, the working of dual slope and single slope integrating adc is explained. 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. Therefore, the columnparallel singleslope architecture fig. Errors due to currentsource output impedance and leakage current comparator must handle large commonmode input. We explain why the slightly more complicated dualslope adc is generally a better choice of adc than the singleslope converter. The tc500 is the base 16bit max device and requires both positive and negative power supplies. As the name suggests, a dual slope adc produces an equivalent digital output for a corresponding analog input by using two dual slope technique. 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. 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.
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. 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. We now consider the single slope and the dual slope adcs. Dualslope and algorithmic jose silvamartinez singleslope integrating adc precision capacitor c and current source i are required. Dual slope adc is the best example of an indirect type adc. 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. A single adc cell no control or bias circuitry objectives. When the ramp potential crosses the unknown input voltage a comparator changes state. Linear slopeintegrating ad converter texas instruments. An alternative ad conversion technique uses the single slope ad converter. The smallest input step that can be resolved by the adc is the lsb least significant. Speed improvements for dualslope ad converters article pdf available in ieee transactions on instrumentation and measurement im345. Preferably, the adc comprises a single slope adc, wherein each of said subranges of said ramp signals is substantially nonoverlapping. The basic working principle of slope ad resistance measurement is the charging and discharging of a known value capacitor cm through the.
One of the many ad techniques utilized in the late 50s and early 60s was the singleslopeintegrating 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. Each ramp generator may comprise a digitaltoanalog converter configured to ramp the output voltage thereof up in steps. A dualslope integration based analogtodigital convertor. The key advantage of this architecture over the single slope. Columnparallel dualslope integrating adc pdf version. Another common adc is the dualslope converter, which relies on integration. 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. As mentioned previously, the singleslope ad has many similarities to the sar ad.
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. Simple dual slope ad converter dual slope ad converter output and timing dualslope adc consider this circuit. Pdf this article illustrates four techniques applied to the wellknown dualslope analogtodigital converter adc in order to improve its speed of. Here, an unknown input voltage is integrated and the value compared against a known reference value. Vin dualslope integration good accuracy without extreme requirements on components. Slaae10c msp430c11x electricity meters circuit diagram for an electronic meter using msp430 mcu kwh meter ic msp430 emeter slaue10b msp430 slope example. 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. 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. The dual slope 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. Component values are selected on assumption that the licell voltage ranges from 2. All single slope converters are basically voltagetotime or currenttotime converters.
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