CN106936432A - The first order electric capacity calibration method of pipeline ADC - Google Patents

Abstract

The present invention provides a kind of first order electric capacity calibration method of pipeline ADC, possesses following steps：17 intervals are divided into INL curves first, linear fit is carried out to 17 intervals respectively, after slope and intercept that will be tried to achieve according to the slope and intercept of 17 fitting a straight lines of line segment, again fitting a straight line, so as to calculate INL hop values, and output according to INL hop values to pipeline ADC is compensated.The first order Capacitor Mismatch Calibration of the pipeline ADC based on integral nonlinearity curve of the invention, can be on the basis of chip area and electric capacity complexity not be increased, while the indexs such as chip SFDR and SNR can be improved.

Description

The first order electric capacity calibration method of pipeline ADC

Technical field

The present invention relates to a kind of first order electric capacity calibration method of pipeline ADC.

Background technology

At present, high-speed high-precision flow line ADC is the important component of Analogous Integrated Electronic Circuits. Due to manufacturing process, the sampling capacitance in ADC is constantly present unmatched problem, adopts The mismatch of sample electric capacity can cause the linearity of ADC to be deteriorated, and be shown as on frequency spectrum without spuious dynamic State scope (SFDR, Spurious Free Dynamic range) is deteriorated.

Although having the algorithm for proposing Foreground calibration electric capacity both at home and abroad, such as by force comparators Output obtains the saltus step of integral nonlinearity (INL), but these methods need to increase extra hard Part circuit, increases circuit complexity and chip area.

The calibration algorithm for improving SFDR has dynamic capacity matching technique (DEM, dynamic Element matching) technology, shake injection (dither injection) technology.Although they Have preferably improve SFDR effect, but DEM technologies can cause signal to noise ratio (SNR, Signal noise ratio) be deteriorated, that is to say, that DEM technologies be to sacrifice SNR as cost, To improve SFDR.Dither injection needs to inject a random signal so that input signal Amplitude is limited, and sacrifices the amplitude range of input signal.

In this regard, none of these methods in the prior art, can not increase chip area and electric capacity On the basis of complexity, while the indexs such as chip SFDR and SNR can be improved.

The content of the invention

To solve the above problems, the present invention provides a kind of based on integral nonlinearity curve (INL songs Line) pipeline ADC first order Capacitor Mismatch Calibration.

To achieve the above object, the first order electric capacity calibration side of a kind of pipeline ADC of the invention Method, comprises the following steps：

S10, detects the INL curves of the pipeline ADC；

S20, determines 17 intervals on the INL curves；

S30, carries out linear fit, and count respectively respectively to the INL curves in 17 intervals Calculate 17 slope ks of line segment₁, k₂... ..., k₁₇, then calculate 17 slopes except maximum and Outer other 15 average values of slope value of minimum value,

S40, according to the average value of slope in S30, re-searches for 17 intervals, Again the values of intercept b of each fitting a straight line is tried to achieve；

S50, according to the average value of slope, and values of intercept b, enters again to 17 intervals Row linear fit, calculates each section of INL hop value of line segment；

S60, the INL hop values in S50 add the INL to ADC export structures Hop value, so that the jump position of ADC transmission curves described in polishing；

Whether S70, the hop value value of the INL curves after detection polishing is more than 1LSB, if judging To be, S20 is repeated.

Specifically, the step S20 specifically includes following steps：

INL curves are divided into 17 hunting zone (X_i, X_i+1), and do not having a search model Enclose (X_i, X_i+1) middle determination last set point (S_i, S_i+1), the abscissa between the Searching point It is fixed apart from X, from S_i=X_iPoint starts, and the INL calculated between the two Searching points is poor Value, with latter two Searching point to one unit of right translation, calculates between the two Searching points INL differences, repeat this step, until S_i+1=X_i+1When, some INL differences can be obtained, really Determine S during INL differences maximum_iAnd S_i+1Position, and according to S in each interval_iAnd S_i+1's Position, repartitions 17 intervals.

The S40 specifically includes following steps：

S41, is set in (S₀, S₁) interval in intercept hunting zone (b₀, b₁), so as to obtain in (S₀, S₁) interval in fitting a straight line expression formula：

S42, is x in abscissa₀When, if the point on INL curves is P (x₀, f (x₀)), intend Close solid line on point P1 be

S43, defines evaluation criterion T：

S44, intercept b change to b1 from b0, obtain a series of evaluation criterion T, take evaluation mark Intercept b when quasi- T values are minimum is used as the interval (S₀, S₁) interval in fitting a straight line intercept.

S45, repeats step S41~S44 and obtains cutting for fitting a straight line in all 17 intervals Away from

The first of pipeline ADC based on integral nonlinearity curve (INL curves) of the invention Level Capacitor Mismatch Calibration, can on the basis of chip area and electric capacity complexity is not increased, The indexs such as chip SFDR and SNR can be improved simultaneously.

Brief description of the drawings

Fig. 1 is the first order electric capacity calibration method flow chart of pipeline ADC of the invention；

Fig. 2 is the INL curve maps of pipeline ADC；

Fig. 3 is the search results map of first region of search；

Fig. 4 is the result figure that first region of search determines；

Fig. 5 is the first time fitting a straight line figure in Fig. 3；

During Fig. 6 is for the first time fitting a straight line in Fig. 3, cut for first fitting a straight line Away from the schematic diagram of search；

Fig. 7 is that the schematic diagram of final result search is carried out for next fitting a straight line in Fig. 5；

Fig. 8 is the line segment schematic diagram after 17 second of interval fitting a straight lines；

Fig. 9 is the ADC input and output figures after compensation.

Specific embodiment

Below, with reference to accompanying drawing, structure of the invention and operation principle etc. are made further It is bright.

As shown in figure 1, the first order electric capacity calibration method of the pipeline ADC of present embodiment, Comprise the following steps：

S10, detects the INL curves of pipeline ADC, specially shown in Fig. 2；

S20, determines 17 interval (S on INL curves₀, S₁)(S₁, S₂)……(S₃₁, S₃₂)；

Specifically, step S20 is comprised the following steps：

As shown in Fig. 2 a hunting zone is set in INL curves, such as in Fig. 2 X₁~X₂, and determine last set point (S₁, S₂), in order to avoid the meter caused by dynamic deflection Error is calculated, the abscissa between the Searching point is fixed apart from X, from S₁=X₁Point starts, Calculate the INL differences d between the two Searching points, subsequent Searching point to one unit of right translation, In hunting zone (X₁, X₂), i.e. S_iFrom X₁Point movement, until S_i+1=X_i+1During, in Some INL differences d can be obtained, S during INL differences d maximums is found_iAnd S_i+1Value determine It is S₁And S₂, as shown in figure 3, in hunting zone X₁, X₂The two of middle INL differences d maximums Individual point is respectively S₁、S₂, after the same method, hunting zone is reselected, so as to carry out Search, 17 interval (S are reclassified as to INL curves according to the method₀, S₁)、(S₁, S₂)……(S₃₁, S₃₂)。

S30, linear fit, such as Fig. 4 are carried out to the INL curves in 17 intervals respectively, Obtain 17 slope ks₁, k₂... ..., k₁₇, and 17 slopes are calculated except maximum and minimum Outer other 15 average values of slope value of value,

17 intervals, according to the average value of slope in S30, are re-searched for by S40, are obtained Obtain the values of intercept b of fitting a straight line in each interval；

Specifically, S40 is comprised the following steps：

S41, is set in (S₀, S₁) interval in intercept hunting zone (b₀, b₁), so as to obtain in (S_0, S₁) interval in fitting a straight line expression formula：

S42, is x in abscissa₀When, if the point on INL curves is P (x₀, f (x₀)), intend Close the point P on solid line₁For

S43, defines evaluation criterion T：

S44, intercept b are from b₀Change to b₁, a series of evaluation criterion T are obtained, take evaluation criterion Intercept b when T values are minimum is used as the interval (S₀, S₁) interval in fitting a straight line intercept, Repeat the values of intercept that S41~S44 is found out in each interval.

S50, according to the average value of slope, and intercept, 17 more re-start linear fit As shown in fig. 7, calculating the INL hop values INL in each interval_{jump_i}；

S60, the INL hop values in S50, add to ADC export structures as shown in Figure 8 Upper INL hop values, so that the jump position of polishing ADC transmission curves；

Whether S70, the hop value value of the INL curves after detection polishing is more than 1LSB, if judging To be, S20 is repeated.

More than, schematic description only of the invention, it will be recognized by those skilled in the art that On the basis of without departing from operation principle of the invention, various improvement can be made to the present invention, this Belong to protection scope of the present invention.

Claims (3)

1. the first order electric capacity calibration method of a kind of pipeline ADC, it is characterised in that including Following steps：

S10, detects the INL curves of the pipeline ADC；

S20, determines 17 intervals on the INL curves；

S30, carries out linear fit, and count respectively respectively to the INL curves in 17 intervals Calculate 17 slope ks of line segment 1, k2 ... ..., k17, then calculate 17 slopes except maximum and Outer other 15 average values of slope value of minimum value

S40, according to the average value of slope in S3017 intervals are re-searched for, Again the values of intercept b of each fitting a straight line is tried to achieve；

S50, according to the average value of slopeAnd values of intercept b, to 17 intervals again Linear fit is carried out, each section of INL hop value of line segment is calculated；

S60, the INL hop values in S50 add the INL to ADC export structures Hop value, so that the jump position of ADC transmission curves described in polishing；

Whether S70, the hop value value of the INL curves after detection polishing is more than 1LSB, if judging To be, S20 is repeated.

2. the first order electric capacity calibration method of pipeline ADC as claimed in claim 1, its It is characterised by, the step S20 specifically includes following steps：

INL curves are divided into 17 hunting zone (X_i, X_i+1), and do not having a search model Enclose (X_i, X_i+1) middle determination last set point (S_i, S_i+1), the abscissa between the Searching point It is fixed apart from X, from S_i=X_iPoint starts, and the INL calculated between the two Searching points is poor Value, with latter two Searching point to one unit of right translation, calculates between the two Searching points INL differences, repeat this step, until S_i+1=X_i+1When, some INL differences can be obtained, really Determine S during INL differences maximum_iAnd S_i+1Position, and according to S in each interval_iAnd S_i+1's Position, repartitions 17 intervals.

3. the first order electric capacity calibration method of pipeline ADC as claimed in claim 1, its It is characterised by, the S40 specifically includes following steps：

S41, is set in (S₀, S₁) interval in intercept hunting zone (b₀, b₁), so as to obtain in (S₀, S₁) interval in fitting a straight line expression formula：

$y=\stackrel{\‾}{k}x+b,(S_0\≤x\≤S_1,b_0\≤b\≤b_1);$

S42, is x in abscissa₀When, if the point on INL curves is P (x₀, f (x₀)), intend Close solid line on point P1 be

S43, defines evaluation criterion T：

$T=\underset{x_o=S_1}{\overset{S_2}{\Σ}}|\stackrel{\‾}{k}{x}_0+b-f\left(x_0\right)|;$

S44, intercept b are from b₀Change to b₁, a series of evaluation criterion T are obtained, take evaluation criterion Intercept b when T values are minimum is used as the interval (S₀, S₁) interval in fitting a straight line intercept；

S45, in remaining 16 intervals, repeats step S41~S44 and obtains all 17 The intercept of fitting a straight line in individual interval.