During autozero, the errors in the analog components buffer offset voltages, etc. At the start of the conversion cycle, the capacitor is totally discharged i. The key advantage of this architecture over the single slope. By watching this video, you will learn the following. Dualslope and algorithmic jose silvamartinez singleslope integrating adc precision capacitor c and current source i are required. Singleslope analogtodigital conversion technique using.
The tc500 is the base 16bit max device and requires both positive and negative power supplies. Characteristics of different slope converters an2615 1237 6. Vin dualslope integration good accuracy without extreme requirements on components. An example of sh circuit is given below the role of the capacitor is to be charged. The single and dualslope analog to digital converters.
We now consider the single slope and the dual slope adcs. Although singleslopeintegrators were used in early ads and voltmeters their. Dual slope adc is the best example of an indirect type adc. Pdf the dualslope conversion improvement researchgate. Here, an unknown input voltage is integrated and the value compared against a known reference value.
Each ramp generator may comprise a digitaltoanalog converter configured to ramp the output voltage thereof up in steps. Slaae10c msp430c11x electricity meters circuit diagram for an electronic meter using msp430 mcu kwh meter ic msp430 emeter slaue10b msp430 slope example. For n bit dual slop type of adc, vr 2 n n va total time for conversion of input va is expressed as follows. 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 single slope adc suffers the disadvantage of calibration drift. 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. N digital thermometer decoder circuit converts the compared. 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. To understand the concepts of adcs, types of adc and its.
As a minimum, each device contains the integrator, zero. A key element of the dual slope adc is a capacitor. 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. One of the many ad techniques utilized in the late 50s and early 60s was the singleslopeintegrating converter. Single slope and dual slope adc explained in this video, the working of dual slope and single slope integrating adc is explained. The design goals included simplicity, small size, moderate speed 10khz, current input. As the name suggests, a dual slope adc produces an equivalent digital output for a corresponding analog input by using two dual slope technique. Another common adc is the dualslope converter, which relies on integration. One of the many ad techniques utilized in the late 50s and early 60s was the single slope integrating converter. 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. 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.
The singleslope adc suffers all the disadvantages of the digital ramp adc, with the added drawback of calibration drift. Case 3 a businessman is talking to his sales office in rome. All singleslope converters are basically voltagetotime or currenttotime converters. 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 circuit shown to the right is an example of a multi slope rundown. It has the added advantage of maintaining accuracy in a noisy environment. It is then charged for a certain set time by the input voltage. At the end of this interval, a known reference voltage v r of opposite polarity is applied to the integrator. Thetc500a510514 family are precision analog front ends that implement dual slope ad converters having a maximum resolution of 17 bits plus sign. Speed improvements for dualslope ad converters article pdf available in ieee transactions on instrumentation and measurement im345. By watching this video, you will learn the following topics. These similarities can be seen in the conceptual diagram of a single slope system infigure 2. 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. 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. Simple dual slope ad converter dual slope ad converter output and timing dual slope adc consider this circuit.
A single adc cell no control or bias circuitry objectives. A dual slope integration based analogtodigital convertor hasan krad department of computer science and engineering, college of engineering, qatar university, p. 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 block diagram of a dual slope adc is shown in the following figure. 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 and dual slope adc explained duration. 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. This note explains the use of offset flipping for onthefly calibration of the adc.
Errors due to currentsource output impedance and leakage current comparator must handle large commonmode input. 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. Precise calibration of dualslope adcs application note maxim. 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. As a minimum, each device contains the integrator, zero crossing comparator and proc essor interface logic. The simplest form of an integrating adc uses a singleslope architecture figures 1a and 1b. Adc converter technologies may occasionally convert a spike or dip because it captures the signal repeatedly at a single point in time. The smallest input step that can be resolved by the adc is the lsb least significant.
As mentioned previously, the single slope ad has many similarities to the sar ad. Dualslope integrating adc dual slope integrating adc. 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. Columnparallel dual slope integrating adc pdf version. Simple dual slope ad converter dual slope ad converter output and timing dualslope adc consider this circuit. 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. The dualslope integration type of ad conversion is a very popular method for digital voltmeter applications. Pdf this article illustrates four techniques applied to the wellknown dualslope analogtodigital converter adc in order to improve its speed of. One form of this circuit compares a linear reference ramp to the unknown voltage input see about integrating converters and capacitors. 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. The key advantage of this architecture over the singleslope is. 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.
Linear slopeintegrating ad converter texas instruments. 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. 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. A dualslope integration based analogtodigital convertor hasan krad department of computer science and engineering, college of engineering, qatar university, p. 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. Columnparallel dualslope integrating adc pdf version. 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. We explain why the slightly more complicated dualslope adc is. If high resolution is desired, then the dual slope conversion technique can be employed. 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. We now consider the singleslope and the dualslope adcs. However, it generally has a long conversion time, so we propose an innovative. An260a 20bit1 ppm linear slopeintegrating ad converter. Singleslope adc architecture the simplest form of an integrating adc uses a singleslope architecture.
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. Explain dual slope integration type adc with the help of a. 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. Figure5 depicts block diagram of dual slope integrating type adc. 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. Hence it is called a s dual slope a to d converter. The key advantage of this architecture over the single slope is.
Component values are selected on assumption that the licell voltage ranges from 2. The key advantage of this architecture over the singleslope is that the final. Us10205463b1 dualgain singleslope adc with digital cds. Difference between adc typescounter,flash,sar,dual slope. Single slope adc architecture dual slope adc course hero. Write the disadvantage of single slope integrator adc and. A dualslope adc dsadc integrates an unknown input voltage v. 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. An alternative ad conversion technique uses the single slope ad converter. When the ramp potential crosses the unknown input voltage a comparator changes state. Preferably, the adc comprises a single slope adc, wherein each of said subranges of said ramp signals is substantially nonoverlapping. Integrating adc overview aka ramp and slope adc different flavors, e.
We explain why the slightly more complicated dualslope adc is generally a better choice of adc than the singleslope converter. With the advent of the advanced technology and the need for more. The time it takes for the integrator to trip the comparator is proportional to the unknown voltage t int v in. Both adcs make use of simple opamp circuits and control logic to do most of their work. Dualslope converter timing diagram the advantage of a dualslope adc is that it is not dependent on the correction factor for the rc product. At the end of that time it is attached to the reference voltage sw1 down. Single slope adc architecture dual slope adc architecture. We explain why the slightly more complicated dual slope adc is generally a better choice of adc than the single slope converter. A dualslope integration based analogtodigital convertor. A dual slope adc ds adc integrates an unknown input voltage v.
Jun 01, 2019 in this video, the working of dual slope and single slope integrating adc is explained. The tc514 adds both a negative power supply converter and a 4input. In this video, the working of dual slope and single slope integrating adc is explained. 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. As mentioned previously, the singleslope ad has many similarities to the sar ad.
The dual slope integration type of ad conversion is a very popular method for digital voltmeter applications. 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. 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. 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.
A columnparallel analogtodigital converter was designed for use with cmos active pixel sensors aps. 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. Therefore, the columnparallel singleslope architecture fig. Therefore, the columnparallel single slope architecture fig. The key advantage of this architecture over the singleslope. Us7924207b2 single slope analogtodigital converter. Article pdf available in ieee transactions on instrumentation and measurement. Pdf the dualslope adc dsadc is a type of analogtodigital. Ee247 lecture 19 university of california, berkeley.
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