As a minimum, each device contains the integrator, zero crossing comparator and proc essor interface logic. 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. 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. The output of a microphone, the voltage at a photodiode or the signal of an accelerometer are the examples of the. The dual slope adc provides good accuracy and high resolution but it has sloe conversion time. Columnparallel dual slope integrating adc pdf version. Now the input is integrated for 300ms and the integrated value is 0. It is pretty slow, but its ability to reject highfrequency noise and fixed low frequencies such as. It is pretty slow, but its ability to reject highfrequency noise and fixed low frequencies such as 50 hz or 60 hz makes it.
An adc analogtodigital converter is used to convert an analog signal to the digital format. Slope integrating adc chapter digitalanalog conversion pdf version. The dualslope conversion improvement radojle radetic1, marijana pavlovkagadejev2, nikola milivojevic3 abstract. Slope integrating adc 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. A single adc cell no control or bias circuitry objectives. Precise calibration of dualslope adcs application note maxim. 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. Columnparallel single slope adcs for cmos image sensors martijn snoeij, albert theuwissen, kofi makinwa and johan huijsing. The dual slope adc dsadc is a type of analogtodigital conversion with low input bandwidths. Integrating and algorithmic adcs voltagetotime converters. 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. The basic working principle of slope ad resistance measurement is the charging and discharging of a known value capacitor cm through the. 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. Conventional twostep adc for cmos image sensor requires full resolution noise performance in the first stage single slope adc, leading to high power consumption and large chip area.
A prototype imager using the mrss adc architecture was realized in a 0. The basic function of an adc is to convert a voltage applied to its input into a number. Here, an unknown input voltage is integrated and the value compared against a known reference value. Lets take a look at two of them, single slope adc and deltasigma adc. Then a known reference voltage of opposite polarity is applied to the integrator and is allowed to ramp until the integrator output returns to zero the rundown period. In this work a dll based single slope adc is proposed which can increase the readout. Single slope adc with onchip accelerated continuoustime differential ramp generator for low noise columnparallel cmos image sensor dexue zhang, rami yassine, loc truong, jeff rysinski daniel van blerkom and barmak mansoorian forza silicon corporation, 2947. The time it takes for the integrator to trip the comparator is proportional to the unknown voltage tintvin. 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.
Dual slope converter an integrating adc in which the. This paper gives an overview of the development of columnparallel adcs that enable the highspeed, powerefficient readout of highresolution cmos imagers. One of the many ad techniques utilized in the late 50s and early 60s was the single slope integrating converter. So for a 2v full scale the lsb or the resolution is 1mv. Hence it is called a s dual slope a to d converter. An260a 20bit1 ppm linear slopeintegrating ad converter. How analogtodigital converter adc works integrator. By using a thermistor, temperature can be directly converted to a resistance. Ltc2309 2309fd block diagram features applications description 8channel, 12bit sar adc with i2c interface n industrial process control n motor control n accelerometer measurements n batteryoperated instruments n isolated andor remote data acquisition n power supply monitoring integral nonlinearity vs output code n 12bit resolution n low power. Processor causes the voltage at the input to the opamp circuit to go from 0 v to vref. An example of sh circuit is given below the role of the capacitor is to be charged. Dual slope converter an integrating adc in which the unknown. Like the integrating adc, this architecture can have excellent line rejection.
At the end of this interval, a known reference voltage v r of opposite polarity is applied to the integrator. A dual slope integration based analogtodigital convertor hasan krad department of computer science and engineering, college of engineering, qatar university, p. Timebased analog to digital converters by shahrzad naraghi a dissertation submitted in partial fulfillment of the requirements for the degree of doctor of philosophy. Dual slope adc using noninverting controlled bootstrap. This choice is nevertheless unusual because of single slope s reputation for long conversion time, normally taking 2nbits time steps, where n bits is the adc resolution.
We choose a single slope adc as a candidate for interleaving because of its simplicity, linearity, lowpower operation, small area, and small input capacitance. 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. The dual slope adc is an analogtodigital converter that does its conversion using quite low bandwidth as its input. A dualslope integration based analogtodigital convertor. With the advent of the advanced technology and the need for more. Single slope conversion or integrating conversion is a classical means of implementing an analogtodigital converter adc 1, and has the advantage of having a very simple implementation with minimal analog content. 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. Integrating adcs ece614 advanced analog ic design presented by antonio oblea may 7, 2008. An alternative ad conversion technique uses the single slope ad converter. The time it takes for the integrator to trip the comparator is proportional to the unknown voltage t int v in.
For example, a sound picked up by a microphone into a digital signal. Twostep single slopesar adc with error correction for cmos. 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 and algorithmic jose silvamartinez single slope integrating adc precision capacitor c and current source i are required. Speed improvements for dual slope ad converters article pdf available in ieee transactions on instrumentation and measurement im345. It is possible to avoid using a dac if we substitute an analog ramping circuit and a digital. But, to achieve a highspeed operation without using a highspeed clock is almost impossible. Us7924207b2 single slope analogtodigital converter. In single slope adc, using a gray code counter is a popular scheme for time digitization, in which the. Dual slope or integrating type adc watch more videos at lecture by.
This note explains the use of offset flipping for onthefly calibration of the adc. 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 possible to avoid using a dac if we substitute an analog ramping circuit and. This paper presents an 11bit twostep single slope successive approximation register sar adc scheme for cmos image sensor applications. Though the operation is quite slow, it has the ability to. However they also used a relatively low frequency for there reference modulation and thus had a slightly different jitter requirement from more modern integrating adcs that switch there currents more often. 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 characteristic to measure with a slope adc is resistance. Errors due to currentsource output impedance and leakage current comparator must handle large commonmode input.
In this video, ankit goyal cofounder at kreatryx and air 1 in gate 2014 explains the working of dual slope adc and the conversion time for this adc. 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 integrating adc in which the unknown signal is converted to a proportional time interval, which is then measured digitally. Ein analogdigitalumsetzer ist ein elektronisches gerat, bauelement oder teil eines. 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. One form of this circuit compares a linear reference ramp to the unknown voltage input see about integrating converters and capacitors. This is done by integrating the unknown for a predetermined length of time. If the output of the counter is a binary number, it will therefore be a binary representation of the input voltage. Feb 24, 2014 a video by jim pytel for renewable energy technology students at columbia gorge community college. Pdf dual slope adc design from power, speed and area. Ltc2309 8channel, 12bit sar adc with i2c interface. A plurality of ramp signals are generated which define nonoverlapping subranges of the full input range.
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. 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. 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. Many of us consider the adc to be a mysterious device. Request pdf dual slope adc using noninverting controlled bootstrap circuit this article presents the simple and inexpensive method to realize the dualslope analogtodigital converter adc. The tc500 is the base 16bit max device and requires both positive and negative power supplies. 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. Therefore, the columnparallel single slope architecture fig. Lowpower and compact successive approximation adc for bio. The old solartron dmms used a pll to lock to the power line frequency.
The single slope ss adc is a simplified architecture. It can, however, be considered very simply to be the instrument that it is. Measurements demonstrate that the conversion speed of an mrss adc is 3. A video by jim pytel for renewable energy technology students at columbia gorge community college. 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. 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. Measuring a thermistor is a good way to demonstrate the functions of a slope adc. When the ramp potential crosses the unknown input voltage a comparator changes state. It also allows input bandwidths in the low mhz range. For each adc channel, the subrange in which the voltage of the input signal falls is determined, and the corresponding ramp signal is selected for use in the a. Pdf r 46 12bit columnparallel singleslope adcs with. The dual slope integration type of ad conversion is a very popular method for digital voltmeter applications. The single slope adc suffers all the disadvantages.
The single slope adc suffers all the disadvantages of the digital ramp adc, with the added drawback of calibration drift. In order to achieve a high speed operation, using a very highspeed clock will increase the power consumption of the adc significantly. Improving single slope adc and an example implemented in fpga. The quad slope multiplier is a multiplying analoguetodigital converter based.
There are a few ways of designing analogtodigital converters using an integrator. Singleslope analogtodigital conversion technique using. The is the basic idea behind the socalled single slope, or integrating adc. The key operating principle of such structures is to translate an input voltage to a. A fascinating question has always been how can you convert an analog voltage to an equivalent digital word. A single slope adc, particularly suitable for use in a massiveparallel adc architecture in a readout circuit of a cmos imager. Temperature measurement, or control, is one of the more common applications of microprocessor systems. The paper deals with the design and construction of a fourquadrant hybrid multiplier using the quad slope technique. Another common adc is the dual slope converter, which relies on integration. Because the analogtodigital converter ad converter or adc has both analog and digital functions, it is a mixedsignal device. It also provides a very lowpower solution and it allows low level signals to be converted. Pdf working with a dualslope adc richard lao riclao. Abstract single slope adc is a common building block in many asci or fpga based frontend systems due to its simplicity, small silicon footprint, low noise interference and low power consumption.
Instead of using a dac with a ramped output, we use an opamp circuit called an integrator to generate a sawtooth waveform which is then compared against the analog input by a comparator. An analogtodigital converter adc is a system that converts an analog signal to a digital signal. Explain dual slope integration type adc with the help of a. Precise calibration of dualslope adcs application note. The dualslope adc dsadc is a type of analogtodigital conversion with low input bandwidths. One of the many interesting architectures available is the dualslope integrator. Introduction if one electronic component is to be nominated as the workhorse inside testandmeasurement equipment, it would be the analogtodigital converter adc. A columnparallel analogtodigital converter was designed for use with cmos active pixel sensors aps.
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