The single and dualslope analog to digital converters. Integrating adc overview aka ramp and slope adc different flavors, e. Single slope and dual slope adc explained duration. Write the disadvantage of single slope integrator adc and. Columnparallel dualslope integrating adc pdf version. 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. The dualslopeconverter features high accuracy, since its performance is independenl of the exact values of rand e. A dualslope adc dsadc integrates an unknown input voltage v. 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. Explain dual slope integration type adc with the help of a. Integrating and algorithmic adcs voltagetotime converters. 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. Single slope adc architecture dual slope adc architecture. Precise calibration of dualslope adcs application note maxim.
The single slope adc suffers the disadvantage of calibration drift. By watching this video, you will learn the following topics. 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. Therefore, the columnparallel singleslope architecture fig. A key element of the dual slope adc is a capacitor. The singleslope adc suffers all the disadvantages of the digital ramp adc, with the added drawback of calibration drift. Single slope and dual slope adc explained in this video, the working of dual slope and single slope integrating adc is explained. All single slope converters are basically voltagetotime or currenttotime converters. 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. A dualslope integration based analogtodigital convertor hasan krad department of computer science and engineering, college of engineering, qatar university, p. Thetc500a510514 family are precision analog front ends that implement dual slope ad converters having a maximum resolution of 17 bits plus sign.
Jun 01, 2019 in this video, the working of dual slope and single slope integrating adc is explained. In this video, the working of dual slope and single slope integrating adc is explained. The time it takes for the integrator to trip the comparator is proportional to the unknown voltage t int v in. Adc converter technologies may occasionally convert a spike or dip because it captures the signal repeatedly at a single point in time. Slaae10c msp430c11x electricity meters circuit diagram for an electronic meter using msp430 mcu kwh meter ic msp430 emeter slaue10b msp430 slope example. As a minimum, each device contains the integrator, zero. Here, an unknown input voltage is integrated and the value compared against a known reference value. 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. All singleslope converters are basically voltagetotime or currenttotime converters. Figure5 depicts block diagram of dual slope integrating type adc. Ee247 lecture 19 university of california, berkeley.
We explain why the slightly more complicated dualslope adc is generally a better choice of adc than the singleslope converter. 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. 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. 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.
An alternative ad conversion technique uses the single slope ad converter. As the name suggests, a dual slope adc produces an equivalent digital output for a corresponding analog input by using two dual slope technique. Us10205463b1 dualgain singleslope adc with digital cds. Singleslope adc architecture the simplest form of an integrating adc uses a singleslope architecture. Although singleslopeintegrators were used in early ads and voltmeters their. The key advantage of this architecture over the single slope is. Dualslope and algorithmic jose silvamartinez singleslope integrating adc precision capacitor c and current source i are required.
If high resolution is desired, then the dual slope conversion technique can be employed. 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. 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. At the end of that time it is attached to the reference voltage sw1 down. Singleslope analogtodigital conversion technique using. The tc500 is the base 16bit max device and requires both positive and negative power supplies. The dual slope integration type of ad conversion is a very popular method for digital voltmeter applications. One of the many ad techniques utilized in the late 50s and early 60s was the singleslopeintegrating converter. Dual slope adc is the best example of an indirect type adc. Columnparallel dual slope integrating adc pdf version.
One form of this circuit compares a linear reference ramp to the unknown voltage input see about integrating converters and capacitors. N digital thermometer decoder circuit converts the compared. However, it generally has a long conversion time, so we propose an innovative. When the ramp potential crosses the unknown input voltage a comparator changes state. At the start of the conversion cycle, the capacitor is totally discharged i. A dual slope adc ds adc integrates an unknown input voltage v. A dualslope integration based analogtodigital convertor. 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. The key advantage of this architecture over the single slope. Dualslope integrating adc dual slope integrating adc. Preferably, the adc comprises a single slope adc, wherein each of said subranges of said ramp signals is substantially nonoverlapping.
At the end of this interval, a known reference voltage v r of opposite polarity is applied to the integrator. By watching this video, you will learn the following. Article pdf available in ieee transactions on instrumentation and measurement. The block diagram of a dual slope adc is shown in the following figure. 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. An example of sh circuit is given below the role of the capacitor is to be charged. Another common adc is the dualslope converter, which relies on integration. Difference between adc typescounter,flash,sar,dual slope. 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. 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. A columnparallel analogtodigital converter was designed for use with cmos active pixel sensors aps.
Us7924207b2 single slope analogtodigital 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 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 smallest input step that can be resolved by the adc is the lsb least significant. 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.
We explain why the slightly more complicated dual slope adc is generally a better choice of adc than the single slope converter. We explain why the slightly more complicated dualslope adc is. The basic working principle of slope ad resistance measurement is the charging and discharging of a known value capacitor cm through the. During autozero, the errors in the analog components buffer offset voltages, etc.
Simple dual slope ad converter dual slope ad converter output and timing dual slope 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. We now consider the singleslope and the dualslope adcs. Each ramp generator may comprise a digitaltoanalog converter configured to ramp the output voltage thereof up in steps. The key advantage of this architecture over the singleslope is that the final. Pdf the dualslope conversion improvement researchgate.
A separate ramp generator is preferably provided to generate each ramp signal. The circuit shown to the right is an example of a multi slope rundown. As mentioned previously, the single slope ad has many similarities to the sar ad. A single adc cell no control or bias circuitry objectives. Both adcs make use of simple opamp circuits and control logic to do most of their work. We now consider the single slope and the dual slope adcs. 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. 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. To understand the concepts of adcs, types of adc and its. The key advantage of this architecture over the singleslope is.
Pdf the dualslope adc dsadc is a type of analogtodigital. 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 note explains the use of offset flipping for onthefly calibration of the adc. The dualslope converter, and variants on it, have been refined to a point where. 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. Component values are selected on assumption that the licell voltage ranges from 2. Hence it is called a s dual slope a to d converter.
Errors due to currentsource output impedance and leakage current comparator must handle large commonmode input. These similarities can be seen in the conceptual diagram of a single slope system infigure 2. The key advantage of this architecture over the singleslope. 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. 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. Linear slopeintegrating ad converter texas instruments. Characteristics of different slope converters an2615 1237 6. The tc514 adds both a negative power supply converter and a 4input. 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.
A dual slope adc, on the other hand, averages together all the spikes and dips within the. These similarities can be seen in the conceptual diagram of a singleslope system infigure 2. As mentioned previously, the singleslope ad has many similarities to the sar ad. 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. Singleslope ad example the main components of the singleslope 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. The dualslope integration type of ad conversion is a very popular method for digital voltmeter applications. For n bit dual slop type of adc, vr 2 n n va total time for conversion of input va is expressed as follows. Precise calibration of dualslope adcs application note.
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. An260a 20bit1 ppm linear slopeintegrating ad converter. It is then charged for a certain set time by the input voltage. The design goals included simplicity, small size, moderate speed 10khz, current input.
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. Case 3 a businessman is talking to his sales office in rome. Dualslope converter timing diagram the advantage of a dualslope adc is that it is not dependent on the correction factor for the rc product. It has the added advantage of maintaining accuracy in a noisy environment. With the advent of the advanced technology and the need for more. Vin dualslope integration good accuracy without extreme requirements on components. Speed improvements for dualslope ad converters article pdf available in ieee transactions on instrumentation and measurement im345.
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