But, from the point of systematic angle, is what you need to worry ADC noise —— not just all after all component (include amplifier, voltage fiducial, clock and power source) metropolis generation are these parts of an apparatus opposite —— of a few noise of systematic noise what is accumulating an influence? More important is, can your system solve the signal that you are interested in?

 

Understand systematic noise better to aid you and go to these intellectual application in your design, I am the closest compose a technical article series that the name settles signal ” for “ . This series discussed the common noise source in typical signal catenary, assist understanding through reducing noise and the method that maintain high accuracy to measure.

 

It is 10 the most crucial questions in this series and answer below, can help you begin to use accurate ADC to undertake designing.

 

Will you be in 1. why is the discovery in ADC planted the noise of the type?

 

Total ADC noise has two main component: Quantify noise and thermal noise. The imitate voltage map that quantifies noise to come from will infinite amount arrives the process of the several word code of limited amount (graph 1 left) . Accordingly, any single numbers are outputted but correspondence inputs voltage at counting an imitate, these voltage may differ the lowest of the half is effective (LSB) .

 

Move as a result of the physics of the charge inside conductance body (graph 1 on the right side of) , thermal noise is the inherent phenomenon in all electron component. Unfortunate is, ADC terminal user cannot interfere the thermal noise of parts of an apparatus, because it is a function of ADC design.

 

Graph 1: Quantify noise (left) with thermal noise (right)

 

Thermal noise and quantify noise to whether affect low resolution and high resolution ADC likewise? Read “Δ- of the 1st partΣThe noise brief introduction in ADC understands pertinent information ” .

 

 2.How be measured and to how be measured and appoint ADC noise?

 

ADC manufacturer uses two kinds of methods to measure ADC noise. The first kind of method receives the input weak point of ADC together, in order to measure the little change as a result of the output code that thermal noise brings about. The sine wave that the 2nd kind of method involves an input to have specific extent and frequency (1 VPP is below 1kHz for example) report how ADC quantifies sine wave. Graph the sound measurement of 2 a confusion of voices that showed these types.

 

Graph 2: Sine wave input checks a setting (left) with the input short circuit checks a setting (right)

 

Which kinds of measurement technique does every kinds of ADC use? Noise measurement technique and normative more information are concerned in reading the 2nd portion please.

 

3.How much is the optimal noise parameter that is used at systematic noise analysis?

 

To ADC noise analysis, I suggest to use input reference noise. I am added thick this phrase, because use an input,referenced noise defines ADC function and not common. Actually, most engineer talks about relevant parameter only, mix effectively for example the resolution that does not have noise, and when them cannot when changing these values greatly, can feel anxious most. After all, if you just use 24 ADC to implement the efficient resolution of 16 ADC, the feeling is in like you buy sheet for the ADC property that won’t use actually.

 

But, the efficient resolution of 16 ADC can not inform your ADC to will use how old full span range certainly (FSR) . That is to say, you may need 16 efficient resolution only, but if signal of the smallest input is 50 NV, cannot use 16 ADC to solve a problem. Accordingly, the real benefit of high resolution Δ-ΣADC is the low input that it can offer referenced noise level. It is not important that this does not mean effective solution – just it is not the optimal way that parameter changes a system.

 

The 3rd part uses the design example that consults without noise resolution and input noise defines systematic noise parameter to adopt these requirements further. Which kind of can you achieve the solution with the fastest, the strongest adaptability? Read an article to discover the answer.

 

4.What is ENBW, why is it very important?

 

In term of common signal processing, the effective noise bandwidth of filter (ENBW) the cut-off that is ideal actual filter frequency FC, its noise power is equal to the noise power H(f) of primitive filter approximately.

 

As analogy, you can consider the night in chill the circumstance in your home. Save fund to reduce energy cost, the cold air that you need to shut door window as far as possible to be entered in order to restrict is measured. Below this kind of circumstance, your home is a system, your door window is filter, cold air is noise, ENBW is the door window that measures you it is how to be opened (or shut) . Gap is bigger (ENBW) , in entering the home (system) cold air (noise) more, vice versa, if pursue,3 are shown.

 

Graph 3: Wide ENBW can produce more noise (left) ; Narrow ENBW produces fewer noise (right)

 

What system component has contribution to ENBW? Read the 4th portion in order to know more news.

 

5.How are you calculated systematic noise bandwidth?

 

If your signal catenary has many filter package, all and downstream filter in must adopting assorted signal chain will calculate the ENBW of every component. Want to combine filter, it is their scale extent please (it is an unit with decibel) the relation with frequency, next pointwise is added.

 

For example, want computation to pursue 4 in the noise contribution of amplifier, you must the bandwidth amplifier and fight mix the number that folds filter, ADC filter is united in wedlock with any aftertreatment filter. Below this kind of circumstance, you but oversight electromagnetism is disturbed (EMI) filter, because it is opposite,be located in upper reaches at amplifier.

 

Graph 4: Show the typical signal cable length of source of many filter wave

 

This may be very complex, read the 5th part to learn ENBW approximate method to be analysed in order to simplify please.

 

If 6. adds exterior amplifier the input end of ADC, how can this affect systematic noise performance?

 

Through mixing ADC amplifier and respective noise source departure can undertake noise is analysed easily. Below this kind of circumstance, you can build the system the model not to have noise ADC to be mixed without noise amplifier, buy condition is voltage source is equal to both input before referenced noise, if pursue,5 are shown.

 

Graph 5: “ passes the buy before reference inputs total noise without noise ”ADC and amplifier

 

Unfortunate is, measures output noise must consult afresh input, because input referenced noise,be the standard that uses in manual of most ADC data. Hypothesis amplifier and ADC noise are not relevant, use two values please with root (RSS) will always output referenced noise certainly. The gain GAMP that you still need to pass amplifier will adjust amplifier noise. Formula shows 1 times output referenced noise for what reach:

 

 

How to input its translate into referenced noise? What is the consequence of GAMP of gain scale factor? Read the 6th portion in order to know relevant news.

 

7.Whether to put in the circumstance with overmuch gain?

 

In article of the 7th series, I examined a give typical examples, this give typical examples added many exterior amplifier in the input end of ADS1261, measured final noise performance. Next, I use my compositive but the function of base line noise these combination and ADS1261 undertook amplifier of process designing gain compare. To be compared more easily, the scale below the different gain setting that I combine in every kinds noise, this offerred several view that add accurate ADC to affect function and function how to change along with gain about will exterior amplifier. Graph 6 described this give typical examples.

 

Graph 6: Compare the noise function of different amplifier and the relation with ADS1261 according to gain

 

This give typical examples and graph what crucial point do 6 chart have? Read noise of amplifier of “ of the 7th part to Δ-ΣThe influence ” of ADC knows more news.

 

8.How to calculate the lung-power of referenced a confusion of voices that passes into a system?

 

The size that consults one of features with the most interesting noise are the ADC FSR that it can use as you appears linear change: If input signal is very small, won’t observe too much and referenced noise – because this may use bigger noise,undertake reference. Or, the scale in if input signal,be more than, can anticipate referenced noise takes dominant place. Below this kind of circumstance, ensure ADC noise and referenced noise are had from beginning to end please can compare a gender. Graph scale of 7 qualitative ground the referenced noise that regards FSR utilization rate as function, ADC noise and total noise.

 

Graph 7: The referenced noise that regards FSR utilization rate as function, ADC noise and total noise

 

The crucial point on this graph – what do A, B and C represent? Change an input signal and how to change systematic gain to you can affect referenced noise? The solution of these problems is found in the 8th part

 

Origin: Heart state apparatus Author: Bryan Lizon