The parameters of dynamic comparators were simulated and surveyed by the cadence virtuoso xl and hspice software in nmcmos 180 technology. A novel lowpower, lowoffset, and highspeed cmos dynamic. Because of this reason, the inputreferred latch offset voltage is one of. The topology of the proposed comparator circuit as shown in fig. It consists of double tail latched comparator, offset cancellation capacitors. As a result, the proposed latch comparator is able to propagate as faster as 4. High speed and low offset comparator for ad converter.
The montecarlo simulation results for the designed comparator in 0. Design of high speed and low offset dynamic latch comparator in 0. This large output voltageis to overcome the latch offset voltage which in turn reduces the kickback noise 5. A novel high speed cmos comparator with low power dissipation, low offset, low noise and high speed is proposed. In a typical design, the mismatches between m 3 and m. A 500 mhz low offset fully differential latched comparator. Strong arm latch has been designed by koubashi in 1993 razavi, b. The proposed offset compensation technique for latch comparator enables the preamplifier design relaxation for highspeed and highresolution analogtodigital converters. The use of a track and latch minimizes the total number of gain stages required for. Differential reference m7, m8 operate in triode region preamp gain 10 input buffers suppress kickback. Design of high speed and low offset dynamic latch comparator in.
Keywords offset cancelation, sense amplifiers, clocked comparators, latch circuits. Different type of comparator circuits like latch type voltage sense comparator, dynamic two stage. My understanding is that varying the value of the potentiometer causes the opamp to saturate towards one of the rail voltages the first led lighting up with positive voltage, and the second led lighting up with negative voltage. Employing the negative resistance of regeneration latch to enhance the comparator gain in input tracking phase is the. According to the above analysis, the main offset voltage. Section 2 describes the different stages of comparator, section 3 represents the simulation result of comparator design along.
Vcm proposed comparator the proposed comparator using a new dynamic offset cancellation technique is shown in figure4 and figure5 shows its transient response obtained from simulation. An offset cancelation technique for latch type sense. High speed and low power dynamic latched comparator for ptl. Offset if operating as a sense amplifier or a comparator, the strongarm latch must achieve a sufficiently small inputreferred offset voltage. The designed comparator achieves zero setup time at a clock frequency of 1. Latched comparator eecs instructional support group. March 2014 design of double tail comparator for high speed adc. In order to decrease circuit complexity, a comparator should maintain power, speed, resolution and offset voltage properly.
For many applications, cmos dynamic latch comparators are very popular due to fastspeed, lowpower consumption, highinput impedance and fullswing output. A fully differential latched comparator using a new offset cancellation technique is presented. How can someone find out resolution of comparator in cadence. The opamp models in the ltspice library have their offset voltages and offset currents set to zero. Offset associated with a specific amp can be cancelled by storing it in series with either the input or the output of that stage offset can be cancelled by adding a pair of auxiliary inputs to the amplifier and storing the offset on capacitors connected to the aux. Based on preamplifier latch comparator, there is an ultra high speed and low offset comparator presented by the analysis of speed and offset voltage. Figure 6 doubletail latchtype voltage sense amplifier 7. Circuit intricacy, speed, low offset voltage, and resolution are essential factors for highspeed applications like analogtodigital converters adcs.
Employing the negative resistance of regeneration latch to enhance the comparator gain in input tracking phase is the key idea to reduce the latch input. The operation of this circuit can be explained as follow. However, an inputreferred latch offset voltage hence offset voltage, resulting from the device mismatches such as threshold voltage vth, current factor. I use output of that to enabledisable some other chips. The method relies on a montecarlosimulation with certain comparator input values and some postprocessing of the comparator output data. Graupner a 2006 a methodology for the offset simulation of comparators. Design and simulation of a high speed cmos comparator. Compared to the proposed dynamic latch comparator has less offset voltage. High speed and low power dynamic latched comparator for. The output of the flipflop q is the latched output. Also, the offset and noise of the latch and offset cancellation. Characterization of the comparator outline static characterization dynamic characterization summary lecture 360 characterization of comparators 4402 page 3602. Proposed comparator 1s result analysis is shown below. The circuit consists of constantgm railtorail commonmode operational transconductance amplifier followed by a regenerative latch in a track and latch configuration to achieve a relatively constant delay.
An input referred latch offset voltage, resulting from threshold voltage vth, current factor. I have designed a 10bit pipeline adc, the subadc need many comparator as you know. The simulation of the fig3 dynamic track and latch comparator circuit has been simulated in the cadence tools environment. The lt1016 is an ultrafast 10ns comparator that interfaces directly to ttlcmos logic while operating off either 5v or single 5v supplies. It consists of a preamplifier a 1, active on the tracking mode of operation, and a latch. Same size transistors are used in the conventional and the proposed.
Tight offset voltage specifications and high gain allow the lt1016 to be used in precision applications. We apply a small step to the comparator input at time. In this comparator, the offset voltage has two sessions, which can be expressed by equation 6. An improved low offset latch comparator for highspeed. Design of high performance cmos dynamic latch comparator. An improved low offset latch comparator for highspeed adcs. A new cmos differential latched comparator suitable for low voltage, lowpower application is presented. The simulation of the test bench of comparator window in fig 5. Effect of apparent offset in discretetime comparators. Ah 439444 objective the objective of this presentation is. Conventionally, to decrease the offset voltage, a preamplifier has been utilized. A simulation method for accurately determining dc and dynamic. A low offset dynamic comparator with morphing amplifier.
Transistors m 1 to m 4 are the input transistors that unbalanced the latch inverters. An offset cancelation technique for latch type sense amplifiers. Designing and simulation of low and rapid voltage comparator. Samid l, volz p, manoli y 2004 a dynamic analysis of a latched cmos comparator. Optimum design of a doubletail latch comparator on power. Pdf design of high speed and low offset dynamic latch. As it provides a larger voltage gain up to 22 vv to the regenerative latch, the inputreferred offset voltage of the latch is reduced and metastability is improved.
To reduce the simulation time during the offset evaluation, we have developed a closedloop method based on a binary search algorithm which shows a fast convergence to the actual comparator threshold. In fig4 sense amplifier was used to recover both voltage swing and performance. Design and analysis of low power and high speed dynamic latch comparator in 0. An ultralow voltage comparator with improved comparison time. Characterizing isf in simulation and measurement fig. Design techniques for highspeed, highresolution comparators. The performance has been analyzed using hspice simulator. In this paper, dynamic comparator offset is determined to the extent of high accuracy among the comparators studied the dynamic comparator which has a back to back latch stage has the. Design of low power preamplifier latch based comparator. Design and implementation of dynamic track and latch. The effect of kickback noise can be significantly reduced by using a preamplifier stage.
The comparator operates in both the track and latch. This in general is difficult as the output of a comparator is discrete valued. Research article a highspeed and lowoffset dynamic latch. The offset occurs due to the mismatch of cox and vth and also by parasitic capacitances. Simulation results of comparator design in this section simulation results are presented and the circuit is simulated using 90 nm cmos technology. The pre amplifier stage is used to decrease the latch offset voltage and it can also amplify a small input voltage difference to a large output voltage. In the cmos comparator offset cancellation is used in both a singlestage preamplifier and a subsequent latch to achieve an offset of less than 300 pv at comparison. The fig5 depicts the transient response of the track and latch dynamic comparator functionality. Now i want to know how to simulate the gain and offset of dynamic comparator.
Im trying to model a comparator circuit we had to build for a lab in my electronics and circuits course using an opamp and potentiometer. When the latch control signal is low, the comparator is on the reset cycle. Latched comparator eecs instructional support group home page. The simulated result shows that the designed comparator has 8bit resolution and dissipates 158. Low powerlow voltage high speed cmos differential track and. The pre amplifier stage is used to decrease the latch offset voltage and it can also. Latched comparator eecs instructional support group home.
Inputs are reconfigured from typical differential pair comparator such that near equal current distribution in the input transistors can be achieved for a metastable point of the comparator. Im using lm3419 as bargraph driver chip and i need a circuit that would latch when top graph led turns on and stay untill bottom led turns off. Engineering strategic research program under r263000a02731. The comparator is implemented with saed 32nm technology libraries. Circuit intricacy, speed, lowoffset voltage, and resolution are essential factors for highspeed applications like analogtodigital converters adcs. A novel dynamic latched comparator with offset voltage compensation is presented. The proposed comparator uses one phase clock signal for its operation and can drive a larger capacitive load with complementary version of the regenerative output latch stage. Comparator using an op amp not simulating properly modeling.
Comparator example used in a pipelined adc with digital correction. Jul 21, 2010 this paper presents a new highspeed and low offset latch comparator. Simulation results are given verifying the operation for sampling a 5 gbs signal dissipating only 360. Like the lt1016, lt1116 and lt1671, this comparator has complementary outputs designed to interface directly to ttl or cmos logic. In the future one can reduce the input referred latch offset voltage, power consumption, hysteresis response. A methodology for the offsetsimulation of comparators.
To achieve a lowpower, highspeed, low offset and, small size comparator, the multiobjective inclined. In this research, propagation delay sets the maximum frequency of operation for the latch signal of the proposed dynamic latch comparator. The comparator is designed and simulated by cadence specture in tsmc 0. A simple methodology for determining the input referred offset voltage of comparators is presented. In these conditions, reaching a 1mv precision during pvt variation characterization accuracy 1mv would need 400 cycles spanaccuracy per simulation run. This comparator is much better than other previous comparators. A lownoise selfcalibrating dynamic comparator for high. The circuit is a regenerative comparator where m 5m 10 and m 6m 11 are the two inverters of the latch net and m 7, m 8, m 9 and m 12 work as switches. Abstractthis paper presents a simulationbased method for evaluating the static offset in. A study on the offset voltage of dynamic comparators. Low powerlow voltage high speed cmos differential track. The bicmos comparator consists of a preamplifier followed by two regenerative stages and achieves an offset of 200 pv at a 1omhzclock rate while dissipating 1. Cadence virtuoso xl layout editing software is used for the layout.
By the analytical expression and simulation through bsim3 and spice level 1 it is reduced6. Inputs are reconfigured from typical differential pair comparator such that. This paper presents an optimum design of a doubletail latch comparator based on transistor sizing with a great certainty to reach the best possible design due to using hspice as a software simulator linked with a heuristic algorithm. Jul 09, 2014 the montecarlo simulation results for the designed comparator in 0. Low power and low offset comparator using latch load.
Latch comparator all the transistors should be properly matched in layout and biased in the saturation region to make a dynamic latch comparator more vigorous against mismatch and process variations. International journal of advanced research in electronics. The use of a track and latch minimizes the total number of. Lm3914 pulls constant current through leds, but i dont know what leds at what current i will use, hence arbitrary high and low levels. Introduction the two inputs of the differential input and sometimes could latch type sense amplifiers are commonly used in. Design of high speed and low offset dynamic latch comparator. Matched complementary outputs further extend the versatility of this comparator. The lt94 is an ultrafast 7ns comparator with complementary outputs and latch. This comparator is designed using 180nm cmos technology with a power supply of 1. Oct 09, 2014 the comparator is designed using differential input stages with regenerative sr latch to achieve lower offset, lower power, higher speed and higher resolution.
So the proposed comparator shows reduced delay and hence it will show better speed as compared to the comparators discussed in 4. Closedloop simulation method for evaluation of static offset. A comparative analysis of high speed dynamic comparator in. Transistor sizing is one of the most critical parts of comparator design which has a significant influence on comparator specifications. Closedloop simulation method for evaluation of static. A clocked comparator model based on the isf bandwidth is found from the fourier transform of the isf.
Comparator design largely depends on the target application. By using simulation algorithm of rf circuit simulation the sampling and decision operation of clock comparator random decision errors are removed. In this research, a novel topology of dynamic latch comparator is illustrated, which is able to. Offset voltage and offset current the ltspice opamps library contains linear technology opamp models, an ideal opamp opamp, and a generic nonideal opamp universalopamp2. Since you have a latch in the circuit, it is nonlinear. Tech students, department of ece, k l university vijayawada, india 2, 3, 4 department of ece, k l university vijayawada, india abstract comparators are basic. This paper presents a new highspeed and low offset latch comparator.
High speed and low power dynamic latched comparator for ptl circuit applications n. Design and implementation of high speed latched comparator m. Design of lowoffset voltage dynamic latched comparator. Summary last lecture university of california, berkeley. Several highspeed comparators like multistage open loop comparator.
The comparator circuit with preamplifier increases the power dissipation, as it requires higher amount of currents than the latch circuitry. I want the comparator to latch up when the input signal goes over 5v and keep latched until the circuit is powered off. Simulations show that this novel dynamic latch comparator designed in 0. A fully di erential dynamic latch comparator basedoncrosscoupleddi erentialpairsisshownin figure, which is based on the design of lewisgray dynamic. Latched comparator, strong arm latch, high speed, low power 1. As explained in the previous section, the precharge action of ss 14 in figure 1b keeps m 36m off initially, thereby reducing their offset contribution.
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