Category Archive : Flash adc in matlab

2 Oct, 2012 | Kazrakazahn | Comments

Flash adc in matlab

Documentation Help Center. Simulate and analyze performance metrics of analog to digital data converters. Modify ADC parameters until you reach your desired system specifications. Use Measurements and Testbenches to validate your design.

This simple ADC highlights some of the typical impairments introduced in an analog-to-digital converters such as aperture jitter, nonlinearity, quantization, and saturation. To better approximate real-world performance, you can individually enable the impairments in the model.

Model a 6-bit Subranging ADC with pipelining and an error correcting second stage. This interleaved ADC model highlights some of the typical impairments introduced by data converters and their effects on a larger system.

You can measure the metastability probability impairment to validate your implementation. The example also shows the effect of metastability on the dynamic performance of the flash ADC. When the digital output from a comparator is ambiguous neither zero nor onethe output is defined as metastable. The ambiguous output is expressed as NaN.

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Another subsystem reports the metastability probability on the fly. Choose a web site to get translated content where available and see local events and offers. Based on your location, we recommend that you select:. Select the China site in Chinese or English for best site performance. Other MathWorks country sites are not optimized for visits from your location.

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Off-Canvas Navigation Menu Toggle. Trials Trials Actualizaciones de productos Actualizaciones de productos. Blocks expand all Building Blocks. Sampling Clock Source Generate clock signal with aperture jitter.

ADC Reference Architectures. DAC Reference Architectures. Open Script. Open Model. Subranging ADC. Select a Web Site Choose a web site to get translated content where available and see local events and offers.

Select web site. Sampling Clock Source.It is formed of a series of comparators, each one comparing the input signal to a unique reference voltage. The comparator outputs connect to the inputs of a priority encoder circuit, which then produces a binary output. The following illustration shows a 3-bit flash ADC circuit:. V ref is a stable reference voltage provided by a precision voltage regulator as part of the converter circuit, not shown in the schematic. As the analog input voltage exceeds the reference voltage at each comparatorthe comparator outputs will sequentially saturate to a high state.

The priority encoder generates a binary number based on the highest-order active input, ignoring all other active inputs. When operated, the flash ADC produces an output that looks something like this:. And, of course, the encoder circuit itself can be made from a matrix of diodesdemonstrating just how simply this converter design may be constructed:. Not only is the flash converter the simplest in terms of operational theory, but it is the most efficient of the ADC technologies in terms of speed, being limited only in comparator and gate propagation delays.

flash adc in matlab

Unfortunately, it is the most component-intensive for any given number of output bits. This three-bit flash ADC requires seven comparators. A four-bit version would require 15 comparators. With each additional output bit, the number of required comparators doubles. Considering that eight bits is generally considered the minimum necessary for any practical ADC comparators needed! An additional advantage of the flash converter, often overlooked, is the ability for it to produce a non-linear output.

With equal-value resistors in the reference voltage divider network, each successive binary count represents the same amount of analog signal increase, providing a proportional response.

For special applications, however, the resistor values in the divider network may be made non-equal. This gives the ADC a custom, nonlinear response to the analog input signal. No other ADC design is able to grant this signal-conditioning behavior with just a few component value changes. Don't have an AAC account? Create one now. Forgot your password? Click here.Documentation Help Center.

The reference voltage of each comparator is 1 least significant bit LSB higher than the one below it in the ladder. As a result, all comparators below a certain point will have input voltage greater than the reference voltage, and a logic 1 output. All comparators above that point will have input voltage smaller than the reference voltage, and a logic 0 output.

The output of 2 N -1 comparators are passed through a priority encoder to produce the digital output.

This encoding scheme is called thermometer encoding. Since the analog input is applied to all the comparators at once, the flash ADC architecture is very fast. But the ADC has low resolution and high power requirements due to a large number of resistors required to implement the architecture. External conversion start clock, specified as a scalar. Data Types: fixed point single double int8 int16 int32 uint8 uint16 uint32 Boolean. Determines whether the analog to digital conversion is complete, returned as a scalar.

Number of physical output bits, specified as a unitless positive real integer in the range [1, 26]. Number of bits determines the resolution of the ADC. Select to connect to an external start conversion clock. By default, this option is selected. Frequency of internal start conversion clock, specified as a positive real scalar in hertz. Conversion start frequency Hz determines the rate of the ADC.

flash adc in matlab

This parameter is only available when Use external start clock is not selected. RMS aperture jitter added as an impairment to the start conversion clock, specified as a real nonnegative scalar in seconds.

Set RMS aperture jitter value to zero if you want a clean clock signal. Rising edge — the output is updated with the rising edge of the clock signal. Falling edge — the output is updated with the falling edge of the clock signal. Either edge — the output is updated with both the rising and the falling edge of the clock signal.

Data Converters

Inherit the output polarity and data type from the analog input signal to the ADC. If Output polarity is set to Autothe minimum and maximum values of the output are determined by the polarity of the Input range. If Output polarity is set to Bipolarthe outputs are between -2 Nbits-1 and 2 Nbits-1 If Output polarity is set to Unipolarthe outputs are between 0 and 2 Nbits This parameter is only editable when Match input scale option is deselected.Documentation Help Center.

The reference voltage of each comparator is 1 least significant bit LSB higher than the one below it in the ladder. As a result, all comparators below a certain point will have input voltage greater than the reference voltage, and a logic 1 output. All comparators above that point will have input voltage smaller than the reference voltage, and a logic 0 output. The output of 2 N -1 comparators are passed through a priority encoder to produce the digital output.

This encoding scheme is called thermometer encoding. Since the analog input is applied to all the comparators at once, the flash ADC architecture is very fast. But the ADC has low resolution and high power requirements due to a large number of resistors required to implement the architecture.

External conversion start clock, specified as a scalar. Data Types: fixed point single double int8 int16 int32 uint8 uint16 uint32 Boolean. Determines whether the analog to digital conversion is complete, returned as a scalar. Number of physical output bits, specified as a unitless positive real integer in the range [1, 26]. Number of bits determines the resolution of the ADC. Select to connect to an external start conversion clock.

By default, this option is selected. Frequency of internal start conversion clock, specified as a positive real scalar in hertz. Conversion start frequency Hz determines the rate of the ADC. This parameter is only available when Use external start clock is not selected. RMS aperture jitter added as an impairment to the start conversion clock, specified as a real nonnegative scalar in seconds.

Data Converters

Set RMS aperture jitter value to zero if you want a clean clock signal. Rising edge — the output is updated with the rising edge of the clock signal.

Falling edge — the output is updated with the falling edge of the clock signal. Either edge — the output is updated with both the rising and the falling edge of the clock signal. Inherit the output polarity and data type from the analog input signal to the ADC. If Output polarity is set to Autothe minimum and maximum values of the output are determined by the polarity of the Input range.

If Output polarity is set to Bipolarthe outputs are between -2 Nbits-1 and 2 Nbits-1 If Output polarity is set to Unipolarthe outputs are between 0 and 2 Nbits This parameter is only editable when Match input scale option is deselected.

Unsigned integers and fixed-point types fixdt 0,Nbits are not available when the Output polarity is set to Bipolar or Auto.Documentation Help Center. The reference voltage of each comparator is 1 least significant bit LSB higher than the one below it in the ladder. As a result, all comparators below a certain point will have input voltage greater than the reference voltage, and a logic 1 output.

All comparators above that point will have input voltage smaller than the reference voltage, and a logic 0 output. The output of 2 N -1 comparators are passed through a priority encoder to produce the digital output.

This encoding scheme is called thermometer encoding. Since the analog input is applied to all the comparators at once, the flash ADC architecture is very fast. But the ADC has low resolution and high power requirements due to a large number of resistors required to implement the architecture. External conversion start clock, specified as a scalar.

Data Types: fixed point single double int8 int16 int32 uint8 uint16 uint32 Boolean. Determines whether the analog to digital conversion is complete, returned as a scalar. Number of physical output bits, specified as a unitless positive real integer in the range [1, 26].

Number of bits determines the resolution of the ADC. Select to connect to an external start conversion clock. By default, this option is selected. Frequency of internal start conversion clock, specified as a positive real scalar in hertz.

Conversion start frequency Hz determines the rate of the ADC. This parameter is only available when Use external start clock is not selected. RMS aperture jitter added as an impairment to the start conversion clock, specified as a real nonnegative scalar in seconds. Set RMS aperture jitter value to zero if you want a clean clock signal.

Rising edge — the output is updated with the rising edge of the clock signal.Documentation Help Center. The reference voltage of each comparator is 1 least significant bit LSB higher than the one below it in the ladder.

As a result, all comparators below a certain point will have input voltage greater than the reference voltage, and a logic 1 output.

All comparators above that point will have input voltage smaller than the reference voltage, and a logic 0 output. The output of 2 N -1 comparators are passed through a priority encoder to produce the digital output.

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This encoding scheme is called thermometer encoding. Since the analog input is applied to all the comparators at once, the flash ADC architecture is very fast. But the ADC has low resolution and high power requirements due to a large number of resistors required to implement the architecture. External conversion start clock, specified as a scalar.

Data Types: fixed point single double int8 int16 int32 uint8 uint16 uint32 Boolean.

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Determines whether the analog to digital conversion is complete, returned as a scalar. Number of physical output bits, specified as a unitless positive real integer in the range [1, 26]. Number of bits determines the resolution of the ADC.

flash adc in matlab

Select to connect to an external start conversion clock. By default, this option is selected. Frequency of internal start conversion clock, specified as a positive real scalar in hertz. Conversion start frequency Hz determines the rate of the ADC. This parameter is only available when Use external start clock is not selected.

RMS aperture jitter added as an impairment to the start conversion clock, specified as a real nonnegative scalar in seconds. Set RMS aperture jitter value to zero if you want a clean clock signal. Rising edge — the output is updated with the rising edge of the clock signal. Falling edge — the output is updated with the falling edge of the clock signal. Either edge — the output is updated with both the rising and the falling edge of the clock signal.

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Inherit the output polarity and data type from the analog input signal to the ADC. If Output polarity is set to Autothe minimum and maximum values of the output are determined by the polarity of the Input range. If Output polarity is set to Bipolarthe outputs are between -2 Nbits-1 and 2 Nbits-1 If Output polarity is set to Unipolarthe outputs are between 0 and 2 Nbits This parameter is only editable when Match input scale option is deselected.

Unsigned integers and fixed-point types fixdt 0,Nbits are not available when the Output polarity is set to Bipolar or Auto. Signed integers and fixed-point types fixdt 1,Nbits are not available when the Output polarity is set to Unipolar. Select to enable impairments such as offset error and gain error in ADC simulation. By default, this option is deselected. This parameter is only available when Enable impairments is selected in the Impairments tab.

Flash Parallel type ADC

Position of the failed comparators, specified as a row vector with positive real values. This parameter is only available when Enable impairments is selected. Choose a web site to get translated content where available and see local events and offers.Documentation Help Center.

This example shows how to customize a flash Analog to Digital Converter ADC by adding the metastability probability as an impairment.

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You can measure the metastability probability impairment to validate your implementation. The example also shows the effect of metastability on the dynamic performance of the flash ADC. When the digital output from a comparator is ambiguous neither zero nor onethe output is defined as metastable.

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The ambiguous output is expressed as NaN. Another subsystem reports the metastability probability on the fly. Extract the inner structure of the flash ADC to add customized impairment. Look under the mask to find the flat structure of the ADC. Copy and paste the complete structure to another new blank canvas. Delete the Clock Generator block because it is not used to provide the start conversion clock.

An external Stimuli subsystem is used for that purpose. The flash ADC now consists of two major components:. An N -bit flash ADC uses comparators in parallel. Before the simulation starts, the comparators calculate the individual reference voltages and store them in a vector.

This generates thermometer code similar to the real flash ADC, without the lag from N individual comparator blocks in the model. Trigger type is kept at its default value Rising edge.

Real ADCs handle conversion from thermometer to binary through logic circuits. This subsystem takes the sum-of-elements of the vector stored by the comparators and applies that sum to a lookup table to simulate missing codes, otherwise known as bubbles.

The block resets the signals on the next relevant edge which is why a triggered subsystem is used. Use this code to implement the Metastability Impairment subsystem. Provide the metastability probability that you want to implement through a constant block connected to the Probability port. To measure metastability impairment, count the number of NaNs encountered and divide that by the number of total comparator outputs generated during the complete simulation.

A simple Simulink implementation of metastability probability measurement is:. Ready signal- Receives the ready signal which represents the rate at which the digital conversion is taking place.