One of the many interesting architectures available is the dualslope integrator. An260a 20bit1 ppm linear slopeintegrating ad converter. What would a complete dual slope adc look like inside. It is pretty slow, but its ability to reject highfrequency noise and fixed low frequencies such as. 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. A dual slope adc dsadc integrates an unknown input voltage. 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 video, the working of dual slope and single slope integrating adc is explained. 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. 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. Slope adc analogtodigital converters can be created in a variety of ways. The peak value attained contains the only clue but that is unknown to this type of adc. Ha0118e introduction this example shows how the internal dual slope adc function in the ht46r7xd1 device is used. 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. However, to obtain the increase in resolution, the rate of conversion is increased when compared to the sar ad. 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.
As a minimum, each device contains the integrator, zero crossing comparator and proc essor interface logic. 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. An 8 bit dual slope adc using two2 cascaded 4 bit counters. 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. Using the dual slope ad converter function in the ht46r7xd1. This clever analogtodigital converter adc has been at the heart of the digital volt meter dvm for decades. The dualslope conversion improvement radojle radetic1, marijana pavlovkagadejev2, nikola milivojevic3 abstract. The slope of a line for eaps 0 001 planet earth, eaps 0 y01 planet earth online, eaps 19100 y01 planet earth laboratory online l. Apr 28, 2015 any type with high resolution is good. Well leave out the details of the countercontroller. The output is also extremely simple, just a pulse that needs to be timed which can be done with even the simplest micro controllers. An answer to this calibration drift dilemma is found in a design variation called the dual slope converter. A complete device list and corresponding data sheets or these products can be found at.
With a dualslope adc you effectively get free averaging as the runup integration phase will have this effect. For this application note, we will build a slope converter. Homework and lab assignments in these courses include graphing exercises that involve a best fit straight line approximation least squares fit calculated or estimated to a set of. A columnparallel analogtodigital converter was designed for use with cmos active pixel sensors aps. Using the dual slope ad converter function in the ht46r7xd1 rev. This greatly decreases the area necessary to implement the adc.
By watching this video, you will learn the following. A dualslope adc dsadc integrates an unknown input voltage v. The main purpose was to construct a 16bit dual slope ad converter with an input voltage of 5v. Precise calibration of dualslope adcs application note. Then a reference input is switched to the integrator, which integrates down from the level determined by the unknown until the starting level is reached. A single adc cell no control or bias circuitry objectives. An answer to this calibration drift dilemma is found in a design variation called the dualslope converter. A dual slope adc ds adc integrates an unknown input voltage v.
Figure5 depicts block diagram of dual slope integrating type adc. I have read up about the integrator circuit and think i know how it works. The ex input signal is directly coupled to the comparator input with no filtering. This paper presents an areaefficient and lowpower 12b successive approximation register single slope analogtodigital converter sarss adc for cmos image sensor cis applications. We now consider the single slope and the dual slope adcs. Both adcs make use of simple opamp circuits and control logic to do most of their work.
Since the single slope adc has a large noise margin, the design complexity can be significantly relaxed. An integrating adc in which the unknown signal is converted to a proportional time interval, which is then measured digitally. If a filter was placed at the input substantial time lag due to settling requirements. The single and dualslope analog to digital converters. This work adopts an ultralow power single slope adc scheme as shown in figure 6. A prototype imager using the mrss adc architecture was realized in a 0. Dual slope adcs are used in applications demanding high accuracy. 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. Adc converter technologies may occasionally convert a spike or dip because it captures the signal repeatedly at a single point in time. The sar adc a most modern adc ic and much faster than dual slope and flash adcs since it uses a digital logic that converges the analog input voltage to the closest value.
The advantage of the dualslope adc that the article failed to mention is that it uses the same components for the integrate cycle of the unknown voltage, and compares that against the. Dual slope or integrating type adc watch more videos at lecture by. Delta sigma converter dual slope adc is use for converting analog to digital value. Which types of adc have highest accuracy, flash type, sar. A dualslope adc dsadc integrates an unknown input voltage. You can think of this method as a stop watch of sorts. A fascinating question has always been how can you convert an analog voltage to an equivalent digital word. The timer is used to set a charge up time after which the same timer is used to. The tc500 is the base 16bit max device and requires both positive and negative power supplies. We explain why the slightly more complicated dualslope adc is generally a better choice of adc than the singleslope converter.
The smallest input step that can be resolved by the adc is the lsb least significant. Thetc500a510514 family are precision analog front ends that implement dual slope ad converters having a maximum resolution of 17 bits. Columnparallel dualslope integrating adc pdf version. 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. Precision analog front ends with dual slope adc microchip. Robert kiyosaki 2019 the speech that broke the internet keep them poor. This is done by integrating the unknown for a predetermined length of time.
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. 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. Comparision of different types of adc digital voltmeter 7. The advantages of using the single slope ad converter are increased resolution, which in the case of the 68hc705jp7 is 12 bits, and the simplicity of the design. Therefore, the columnparallel singleslope architecture fig. Elegant in its simplicity, a dsadc dualslope analogtodigital converter employs an analog integrator coupled to a comparator and control logic to accumulate integrate the input signal, v in, for a fixed interval, t1 comprising the first slope then to switch the integrators input to a fixed negative reference, v ref, to. A multichannel single slope adc using tdc scheme built in a lowcost fpga device is shown in fig. Adcs, integrating, multislope, multislope, lcd drivers, led. Inverted dualslope adc boosts dynamic range edn asia. Simply count the time it takes for the integrator voltage to ramp back down to zero volts. 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. 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. There are basically 4 types of analog to digital converter adc.
Write the disadvantage of single slope integrator adc and. Dual slope converter an integrating adc in which the unknown. An example of sh circuit is given below the role of the capacitor is to be charged. Ein analogdigitalumsetzer ist ein elektronisches gerat, bauelement oder teil eines.
The slope converter works by timing the rate that a capacitor charges to a specified voltage. Improving single slope adc and an example implemented in. 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. This note explains the use of offset flipping for onthefly calibration of the adc. The dual slope adc dsadc is a type of analogtodigital conversion with low input bandwidths. During the 2nd slope negative slope the input voltage is disconnected and the counter begins. 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. We now consider the singleslope and the dualslope adcs. We explain why the slightly more complicated dual slope adc is generally a better choice of adc than the single slope converter. The singleslope ad conversion utilizes several unique components. Precise calibration of dualslope adcs application note maxim. The dualslope converter, and variants on it, have been refined to a point where 16 and 17bit resolution units are available.
A quadslope adc multiplier article pdf available in international journal of electronics 552. May 05, 2016 the advantage of the dualslope adc that the article failed to mention is that it uses the same components for the integrate cycle of the unknown voltage, and compares that against the. Linear slopeintegrating ad converter texas instruments. Pdf twostep single slopesar adc with error correction for. Mar 31, 2018 robert kiyosaki 2019 the speech that broke the internet keep them poor. Differential input ports are available in most fpga families today which can be used as comparators in the single slope adc.
Therefore, the columnparallel single slope architecture fig. Dual slope integration converter the conversion begins with the electronic switch in the t 1 position, with the counter reset to zero and the capacitor fully discharged. 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. Difference between adc typescounter,flash,sar,dual slope. The single slope ad conversion utilizes several unique components. 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. 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. 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 dualslope adc dsadc is a type of analogtodigital conversion with low input bandwidths. The purpose of this work was to understudy the functionalities as well as the operations of the various converters adda converters with emphasis laid on the dual slope adcs. Dashed lines mean control to throw a switch or convey a pulse. The input voltage causes the capacitor connected to the opamp to charge at a rate dependent on. Twostep single slopesar adc with error correction for. 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. Integrating or dual slope adc electrical and electronics.
To overcome this sensitivity to the component values, the dualslope integrating architecture is used. Comparision of different types of adcdigital voltmeter 7. 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 a decided disadvantage because most real world signals require some smoothing. To overcome this sensitivity to the component values, the dual slope integrating architecture is used. In the dual slope 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. This is done twice, once with a reference source and once with a sensor. 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 dual slope adc is an analogtodigital converter that does its conversion using.
This circuit consists of a comparator, output latches, successive approximation register sar and da converter. However, it generally has a long conversion time, so we propose an innovative. Dual slope adc is slow but have high accuracy and have high resistance to noise. Each of the the types you have named is used for different application strengths. It is pretty slow, but its ability to reject highfrequency noise and fixed low frequencies such as 50 hz or 60 hz makes it. Two main input referred noise sources of the single slope adc include the ktc noise introduced by capacitor cos during reset phase s1 and the random noise of inverter transistors. Unlike a dualslope,this converter has no inherent noise rejection capability. Dual slope integration converter the block diagram of the dualslope integration converter is shown in figure 28. The design goals included simplicity, small size, moderate speed 10khz, current input. Dual slope converter an integrating adc in which the.
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