Patent Publication Number: US-11641209-B2

Title: Time-interleaved analog to digital converter having randomization and signal conversion method

Description:
BACKGROUND 
     1. Technical Field 
     The present disclosure relates to an analog to digital converter. More particularly, the present disclosure relates to an analog to digital converter having randomization and a noise shaping function and a signal conversion method thereof. 
     2. Description of Related Art 
     In a mixed signal circuit, a capacitor is normally configured to transfer a signal that is stored in a previous phase. However, in practical applications, if mismatches exist in capacitors, the signal cannot be accurately transferred. As a result, the output of the mixed signal may be affected by noises having a harmonic tone, which results in a lower effective resolution of the mixed signal circuit. 
     SUMMARY 
     In some aspects of the present disclosure, a time-interleaved analog to digital converter includes a plurality of capacitor array circuits, at least one successive approximation register circuitry, and at least one noise shaping circuitry. The plurality of capacitor array circuits are configured to alternately sample an input signal, in order to generate a sampled input signal. The at least one successive approximation register circuitry is configured to perform an analog to digital conversion according to the sampled input signal and a residue signal, in order to generate at least one digital output. The at least one noise shaping circuitry is configured to utilize at least one first circuit in a plurality of switched-capacitor circuits to transfer the residue signal from a first capacitor array circuit in the plurality of capacitor array circuits, and randomly select at least one second circuit from the plurality of switched-capacitor circuits to cooperate with a second capacitor array circuit in the plurality of capacitor array circuits to sample the input signal. 
     In some aspects of the present disclosure, a signal conversion method includes the following operations: alternately sampling, by a plurality of capacitor array circuits, an input signal, in order to generate a sampled input signal; performing an analog to digital conversion according to the sampled input signal and a residue signal, in order to generate at least one digital output; utilizing at least one first circuit in a plurality of switched-capacitor circuits to transfer the residue signal from a first capacitor array circuit in the plurality of capacitor array circuits; and randomly selecting at least one second circuit from the plurality of switched-capacitor circuits to cooperate with a second capacitor array circuit in the plurality of capacitor array circuits to sample the input signal. 
     These and other objectives of the present disclosure will be described in detailed description with various figures and drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a schematic diagram of a time-interleaved analog to digital converter (ADC) according to some embodiments of the present disclosure. 
         FIG.  2 A  is a schematic diagram of the time-interleaved ADC in  FIG.  1    that operates during a first phase according to some embodiments of the present disclosure. 
         FIG.  2 B  is a schematic diagram of the time-interleaved ADC in  FIG.  1    that operates during phase k+1 according to some embodiments of the present disclosure. 
         FIG.  2 C  is a schematic diagram of the time-interleaved ADC in  FIG.  1    that operates during phase k+2 according to some embodiments of the present disclosure. 
         FIG.  2 D  is a schematic diagram of the time-interleaved ADC in  FIG.  1    that operates in phase k+3 according to some embodiments of the present disclosure. 
         FIG.  3    is a schematic diagram of a switched-capacitor circuit in  FIG.  2 A  according to some embodiments of the present disclosure. 
         FIG.  4    is a schematic diagram of the pseudo random number generator circuit in  FIG.  1    according to some embodiments of the present disclosure. 
         FIG.  5    is a schematic diagram showing waveforms of the clock signals and the predetermined clock signal in  FIG.  1    according to some embodiments of the present disclosure. 
         FIG.  6    is a flow chart of a signal conversion method according to some embodiments of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     The terms used in this specification generally have their ordinary meanings in the art and in the specific context where each term is used. The use of examples in this specification, including examples of any terms discussed herein, is illustrative only, and in no way limits the scope and meaning of the disclosure or of any exemplified term. Likewise, the present disclosure is not limited to various embodiments given in this specification. 
     In this document, the term “coupled” may also be termed as “electrically coupled,” and the term “connected” may be termed as “electrically connected.” “Coupled” and “connected” may mean “directly coupled” and “directly connected” respectively, or “indirectly coupled” and “indirectly connected” respectively. “Coupled” and “connected” may also be used to indicate that two or more elements cooperate or interact with each other. In this document, the term “circuitry” may indicate a system formed with one or more circuits. The term “circuit” may indicate an object, which is formed with one or more transistors and/or one or more active/passive elements based on a specific arrangement, for processing signals. 
     As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. Although the terms “first,” “second,” etc., may be used herein to describe various elements, these elements should not be limited by these terms. These terms are used to distinguish one element from another. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element, without departing from the scope of the embodiments. For ease of understanding, like elements in various figures are designated with the same reference number. 
       FIG.  1    is a schematic diagram of a time-interleaved analog to digital converter (ADC)  100  according to some embodiments of the present disclosure. In some embodiments, time-interleaved ADC  100  operates as a time-interleaved successive approximation register (SAR) ADC. 
     The time-interleaved ADC  100  includes a switch S 1 , a switch S 2 , a capacitor array circuit CT 1 , a capacitor array circuit CT 2 , at least one noise shaping circuitry  125 , and at least one SAR circuitry  145 . 
     The switch S 1  and the switch S 2  are turned on respectively according to a clock signal Φ S1  and a clock signal Φ S2 , such that an input signal V in  is alternately sampled by the capacitor array circuit CT 1  and the capacitor array circuit CT 2 , in order to generate a corresponding sampled input signal Vin(k). For example, during a phase k, the switch S 2  is turned on and the switch S 1  is not turned on. Under this condition, the capacitor array circuit CT 1  provides the input signal V in (k−1) (not shown), which is sampled in a previous phase k−1, to the at least one SAR circuitry  145  for analog to digital conversion, and the capacitor array circuit CT 2  samples the current input signal V in  to generate a sampled input signal V in (k). Afterwards, in phase k+1, the switch S 1  is turned on and the switch S 2  is not turned on. Under this condition, the capacitor array circuit CT 2  provides the sampled input signal V in (k) to the at least one SAR circuitry  145  for the analog to digital conversion, and the capacitor array circuit CT 1  samples the input signal V in , in order to generate a sampled input signal V in (k+1) (not shown). 
     The at least one noise shaping circuitry  125  is configured to receive a residue signal from the capacitor array circuit CT 1  or the capacitor array circuit CT 2 , in order to perform a noise shaping function. For example, during phase k, the capacitor array circuit CT 2  provides a residue signal Vres(k−1) generated in a previous phase k−1 to the at least one noise shaping circuitry  125 . Afterwards, during phase k+1, the capacitor array circuit CT 1  provides a residue signal Vres(k) (not shown) generated in the previous phase k to the at least one noise shaping circuitry  125 . In some embodiments, the noise shaping function is performed by integrating the residue signal Vres(k−1) and the sampled input signal V in (k). 
     In some embodiments, the at least one noise shaping circuitry  125  may include switched-capacitor circuits (e.g., switched-capacitor circuits Cex1-Cex8 in  FIG.  2 A ). These switched-capacitor circuits are configured to receive the residue signal from the capacitor array circuit CT 1  and the capacitor array circuit CT 2 , and may cooperate with the capacitor array circuit CT 1  or the capacitor array circuit CT 2  to sample the input signal V in . For example, the at least one noise shaping circuitry  125  may utilize at least one first circuit in the switched-capacitor circuits to transfer the residue signal from the capacitor array circuit CT 1  (or the capacitor array circuit CT 2 ), and randomly select at least one second circuit from the switched-capacitor circuits, in order to cooperate with the capacitor array circuit CT 2  (or the capacitor array circuit CT 1 ) to sample the input signal V in . The at least on first circuit is different from the at least one second circuit. The operations regarding herein will be described with reference to  FIG.  2 A  to  FIG.  2 D . 
     The at least one SAR circuitry  145  performs the analog to digital conversion based on the sampled input signal V in (k) and a residue signal Vres(k−1), in order to control a corresponding one of the capacitor array circuits CT 1  and CT 2  to receive a common voltage V refp  and a common mode voltage V refn  to generate at least one digital output (e.g., digital output D out1  and digital output D out2  in  FIG.  2 A ). 
     In some embodiments, time-interleaved ADC  100  further includes a pseudo random number generator circuit  160 , which is configured to generate a pseudo random number Q 4  according to a predetermined clock signal CLK. The at least one SAR circuitry  145  may perform a binary search algorithm based on the sampled input signal V in (k) and the residue signal Vres(k−1) to generate switching signals VS 1 . A first part VS 11  of the switching signals VS 1  is for controlling the capacitor array circuit CT 1  and the capacitor array circuit CT 2 , and a second part VS 12  of the switching signals VS 1  is for controlling switched-capacitor circuits in the at least one noise shaping circuitry  125 . The at least one SAR circuitry  145  further adjusts the second part VS 12  of the switching signals VS 1  according to pseudo random number Q 4 , in order to generate switching signals VS 2 . The at least one noise shaping circuitry  125  may random select the at least one second circuit from the switched-capacitor circuits according to the switching signals VS 2 . Operations regarding herein will be provided with reference to  FIG.  2 A  to  FIG.  2 D . 
     In some embodiments, the at least one SAR circuitry  145  includes at least one control logic circuit (e.g., a control logic circuit  140 B and a control logic circuit  142 B in  FIG.  2 A ) and a randomization circuit. The at least one control logic circuit may be configured to perform the binary search algorithm to generate the switching signals VS 1 . The randomization circuit may adjust the second part VS 12  according to the pseudo random number Q 4 , in order to generate the switching signals VS 2 . In some embodiments, each of the at least one control logic circuit and the randomization circuit may be, but not limited to, implemented with one or more logic circuits, a controller circuit, digital signal processor circuit. 
     In some embodiments, implementations of the time-interleaved ADC  100  can be further understood with reference to a first reference (U.S. Pat. No. 10,778,242) and/or a second reference (U.S. Pat. No. 10,790,843). For example, the capacitor array circuit CT 1  and the capacitor array circuit CT 2  may be the same as a capacitor CT 1  and a capacitor CT 2  in these references. In some embodiments, the at least one noise shaping circuitry  125  may include a switching circuitry  120  of the first reference, or may include noise shaping circuitries  120  and  122  in the second reference. In some embodiments, the at least one SAR circuitry  145  may include the SAR circuitry  140  of the first reference, or may include SAR circuitries  140  and  142  of the second reference. Implementations and operations about the at least one noise shaping circuitry  125  and at least one SAR circuitry  145  can be understood with reference to the above references, and thus the repetitious descriptions are not further given. 
     For ease of understanding, certain implementations and operations of the time-interleaved ADC  100  are described with some embodiments of the second reference, but the present disclosure is not limited thereto. It is understood that various time-interleaved SAR ADCs able to perform the noise shaping function are within the contemplated scope of the present disclosure. For example, in some other embodiments, a terminal (e.g., an electrode of a capacitor) of the at least second circuit, which is randomly selected from the switched-capacitor circuits, may generate a residue signal, and the at least one noise shaping circuitry  125  may perform the noise shaping function to this residue signal. 
       FIG.  2 A  is a schematic diagram of the time-interleaved ADC  100  in  FIG.  1    that operates during the phase k according to some embodiments of the present disclosure. Similar to the second reference, in this example, the at least one noise shaping circuitry  125  includes a noise shaping circuitry  120  and a noise shaping circuitry  122 , in which the noise shaping circuitry  120  includes a capacitor Cint1, and the noise shaping circuitry  122  includes a capacitor Cint2. The noise shaping circuitry  120  and the shaping circuitry  122  commonly includes switched-capacitor circuits Cex1-Cex8. Similar to the second reference, the at least one SAR circuitry  145  includes a SAR circuitry  140  and a SAR circuitry  142 , in which the SAR circuitry  140  includes a quantizer circuit  140 A and a control logic circuit  140 B, and the SAR circuitry  142  includes a quantizer circuit  142 A and a control logic circuit  142 B. Detailed operations about the above circuits can be understood with reference to the second reference, and thus the repetitious descriptions are not further given. 
     During the phase k, the switched-capacitor circuit Cex1 and the switched-capacitor circuit Cex2 are coupled between switches in the capacitor array circuit CT 1  and a node N 1  based on the switching signals VS 2 , in order to perform the analog to digital conversion. In response to this analog to digital conversion, the residue signal Vres(k) (not shown) will be stored in the switched-capacitor circuit Cex1 and the switched-capacitor circuit Cex2. Based on the switching signals VS 2 , the switched-capacitor circuit Cex5 and the switched-capacitor circuit Cex6 are coupled to in parallel with the capacitor Cint1 and capacitor Cint2, respectively, in order to transfer the residue signal Vres(k−1) (not shown) that is generated from the capacitor array circuit CT 2  in the previous phase k−1. 
     Compared with the second reference, the noise shaping circuitries  120  and  122  further includes switched-capacitor circuits Cex7-Cex8. In some embodiments, if the pseudo random number Q 4  is a first logic value (e.g., a logic value of 0), the at least one noise shaping circuitry  125  utilizes the at least one second circuit (which may be the switched-capacitor circuits Cex7-Cex8 in this example) to cooperate with the capacitor array circuit CT 2  to sample the input signal V in , in order to generate the sampled input signal V in (k). Alternatively, if the pseudo random number Q 4  is a second logic value (e.g., a logic value of 1), the at least one noise shaping circuitry  125  utilizes at least one predetermined circuit in the switched-capacitor circuits Cex1-Cex8 (which may be the switched-capacitor circuits Cex3 and Cex4 that are coupled to the at least one noise shaping circuitry  125  during the previous phase k−1; which can be understood with reference to the second reference) to cooperate with the capacitor array circuit CT 2  to sample the input signal V in , in order to generate the sampled input signal V in (k) (not shown). 
     As shown in  FIG.  2 A , in this example, the pseudo random number Q 4  is the logic value of 1. Under this condition, the at least one noise shaping circuitry  125  utilizes the predetermined switched-capacitor circuits Cex3 and Cex4. Accordingly, during phase k, the switched-capacitor circuits Cex3 and Cex4 are coupled between switches in the capacitor array circuit CT 2  and a node N 2  based on the switching signal VS 2 , in order to sample the input signal V in  to generate the sampled input signal V in (k) (not shown). On the other hand, as the switched-capacitor circuits Cex7 and Cex8 are not utilized in phase k (i.e., disconnected from the capacitor array circuit CT 1 , the capacitor array circuit CT 2 , and/or the at least one noise shaping circuitry  125 ), the switched-capacitor circuits Cex7 and Cex8 stand idle. 
       FIG.  2 B  is a schematic diagram of the time-interleaved ADC  100  in  FIG.  1    that operates during phase k+1 according to some embodiments of the present disclosure. It is understood that, phase k+1 is a phase that follows the phase k. 
     During phase k+1, the pseudo random number Q 4  has the logic value of 0. Under this condition, the at least one noise shaping circuitry  125  utilizes the switched-capacitor circuits Cex7 and Cex8 (i.e., the at least one second circuit) which previously stand idle. Accordingly, during phase k+1, the switched-capacitor circuits Cex7 and Cex8 are coupled between switches in the capacitor array circuit CT 1  and the node N 1  based on the switching signals VS 2 , in order to sample the input signal V in  to generate the sampled input signal V in (k+1) (not shown). On the other hand, the switched-capacitor circuits Cex5 and Cex6 are not utilized during phase k+1 and thus stand idle. 
     The switched-capacitor circuits Cex3 and Cex4 coupled between switches in the capacitor array circuit CT 2  and the node N 2 , in order to perform the analog to digital conversion. In response to this analog to digital conversion, the residue signal Vres(k+1) (not shown) will be stored in in the switched-capacitor circuits Cex3 and Cex4. Based on the switching signals VS 2 , the switched-capacitor circuit Cex1 and the switched-capacitor circuit Cex2 are coupled in parallel with the capacitor Cint1 and the capacitor Cint2, respectively, in order to transfer the residue signal Vres(k) (not shown) which is generated during the previous phase k. 
       FIG.  2 C  is a schematic diagram of the time-interleaved ADC  100  in  FIG.  1    that operates during phase k+2 according to some embodiments of the present disclosure. It is noted that, phase k+2 is a phase that follows phase k+1. 
     During phase k+2, the pseudo random number Q 4  has the logic value of 1. Under this condition, the at least one noise shaping circuitry  125  utilizes the predetermined switched-capacitor circuits Cex1 and Cex2 (i.e., the switched-capacitor circuits coupled to the at least one noise shaping circuitry  125  in the previous phase k+1). Accordingly, during phase k+2, the switched-capacitor circuits Cex1 and Cex2 are coupled between the switches in the capacitor array circuit CT 2  and the node N 2  based on the switching signals VS 2 , in order to sample the input signal V in  to generate the sampled input signal V in (k+2) (not shown). On the other hand, the switched-capacitor circuits Cex5 and Cex6 are not utilized in phase k+2 and thus continue standing idle. 
     Based on the switching signals VS 2 , the switched-capacitor circuits Cex7 and Cex8 are coupled between the switches in the capacitor array circuit CT 1  and the node N 1 , in order to perform the analog to digital conversion. In response to the analog to digital conversion, the residue signal Vres(k+2) (not shown) will be stored in the switched-capacitor circuits Cex7 and Cex8. In other words, the switched-capacitor circuits Cex7 and Cex8, which are randomly selected, are utilized to sample the input signal V in  during phase k+1, and are utilized to generate the residue signal Vres(k+2) in a next phase k+2. The switched-capacitor circuit Cex3 and the switched-capacitor circuit Cex4 are coupled in parallel with the capacitor Cint1 and the capacitor Cint2, respectively, based on the switching signals VS 2 , in order to transfer the residue signal Vres(k+1) (not shown) that is generated in the previous phase k+1. 
       FIG.  2 D  is a schematic diagram of the time-interleaved ADC  100  in  FIG.  1    that operates in phase k+3 according to some embodiments of the present disclosure. It is understood that, phase k+3 is a phase that follows phase k+2. 
     During phase k+3, the pseudo random number Q 4  is the logic value of 0. Under this condition, the at least one noise shaping circuitry  125  utilizes the switched-capacitor circuits Cex5 and Cex6 which previously stand idle. Accordingly, during phase k+3, based on the switching signals VS 2 , the switched-capacitor circuits Cex5 and Cex6 are coupled between the switches in the capacitor array circuit CT 1  and the node N 1 , in order to sample the input signal V in  to generate the sampled input signal V in (k+3) (not shown). On the other hand, the switched-capacitor circuits Cex3 and Cex4 are not utilized in phase k+3 and thus stand idle. 
     The switched-capacitor circuits Cex1 and Cex2 are coupled between the switches in the capacitor array circuit CT 2  and the node N 2  based on the switching signals VS 2 , in order to perform the analog to digital conversion. In response to the analog to digital conversion, the residue signal Vres(k+3) (not shown) will be stored in the switched-capacitor circuits Cex1 and Cex2. Based on the switching signals VS 2 , the switched-capacitor circuit Cex7 and the switched-capacitor circuit Cex8 are coupled in parallel with the capacitor Cint1 and the capacitor Cint2, respectively, in order to transfer the residue signal Vres(k+2) (not shown) that is stored in the previous phase k+2. 
     With reference to  FIG.  2 A  to  FIG.  2 D , it is understood that, the at least one noise shaping circuitry  125  may randomly select a group of switched-capacitor circuits according to the pseudo random number Q 4 . This group of switched-capacitor circuits may perform the sampling operation during the current phase, and may store (or generate) the residue signal in a next phase. In some approaches (e.g., second reference), the residue signal is transferred by switching capacitors (e.g., the switched-capacitor circuits Cex1-Cex6 in the second reference) in a predetermined sequence to perform the noise shaping function. In practical applications, if mismatch(es) exist in these capacitors due to non-ideal factors (e.g., process variations), the transfer of the residue signal would be inaccurate. As a result, the output of the analog to digital conversation will be affected by noise(s) having harmonic tone, which results in a lower resolution. Compared with the above approaches, in some embodiments, additional switched-capacitor circuits (e.g., the switched-capacitor circuits Cex7-Cex8) are arranged in the at least one noise shaping circuitry  125 , and one group of switched-capacitor circuits is randomly selected to perform the analog to digital conversion and the noise shaping function. As a result, it is able to avoid transferring the residue signal by utilizing the switched-capacitor circuits in a predetermined sequence in the operating progress, in order to lower impacts from noise(s) having harmonic tone. 
     It is understood that, the above arrangements are given with examples referred to the second reference, but the present disclosure is not limited thereto. For example, the above arrangements may be (but not limited to) replaced with other embodiments in the second reference (or the first reference). If the time-interleaved ADC  100  is implemented with reference to some embodiments in the first reference, each of the at least one first circuit, at least one second circuit, and at least one predetermined circuit is one switched-capacitor circuit. 
       FIG.  3    is a schematic diagram of the switched-capacitor circuit Cex8 in  FIG.  2 A  according to some embodiments of the present disclosure. The switched-capacitor circuits Cex1-Cex8 have the same architecture. Taking the switched-capacitor circuit Cex8 as an example, the switched-capacitor circuit Cex8 includes switches SW 1 -SW 8  and a capacitor C. A first terminal of the capacitor C is coupled to node N 1 , the node N 2 , the node N 1 , and the node N 2  in  FIG.  2 A  via the switch SW 1 , the switch SW 5 , and the switch SW 7  respectively. A second terminal of the capacitor C is coupled to the switches in the capacitor array circuit CT 1 , the switches in the capacitor array circuit CT 2 , a terminal of the capacitor Cint1, and a terminal of the capacitor Cint2 in  FIG.  2 A  via the switch SW 2 , the switch SW 4 , the switch SW 6 , and the switch SW 8  respectively. The switches SW 1 -SW 8  operate as a multiplexer circuit  310 , which may selectively couple the capacitor C to a corresponding circuit according to the switching signals VS 2 , or may set the capacitor C to be idle. 
     For example, when the switches SW 1  and SW 2  are turned on and the remaining switches SW 3 -SW 8  are not turned on, the switched-capacitor circuit Cex8 is coupled between the switches in the capacitor array circuit CT 1  and the node N 1 . When the switches SW 3  and SW 4  are turned on and the remaining switches SW 1 -SW 2  and SW 5 -SW 8  are not turned on, the switched-capacitor circuit Cex8 is coupled between the switches in the capacitor array circuit CT 2  and the node N 2 . When the switches SW 5  and SW 6  are turned on and the remaining switches SW 1 -SW 4  and SW 7 -SW 8  are not turned on, the switched-capacitor circuit Cex8 is coupled in parallel with the capacitor Cint1. When the switches SW 7  and SW 8  are turned on and the remaining switches SW 1 -SW 6  are not turned on, the switched-capacitor circuit Cex8 is coupled in parallel with the capacitor Cint2. 
       FIG.  4    is a schematic diagram of the pseudo random number generator circuit  160  in  FIG.  1    according to some embodiments of the present disclosure. The pseudo random number generator circuit  160  includes a XOR gate circuit  410  and flip flop circuits  420 - 423 . The XOR gate circuit  410  generate a signal Q 0  according to a signal REF 1  and the pseudo random number Q 4 . In some embodiments, each of the flip flop circuits  420 - 423  may be a D-type flip flop circuit. The flip flop circuits  420 - 423  are coupled in series, and sequentially transfer the signal Q 0  according to the predetermined clock signal CLK to generate the pseudo random number Q 4 . For example, the flip flop circuit  420  outputs the signal Q 0  to be a signal Q 1  according to the predetermined clock signal CLK. The flip flop circuit  421  outputs the signal Q 1  to be a signal Q 2  according to the predetermined clock signal CLK. The flip flop circuit  422  outputs the signal Q 2  to be a signal Q 3  according to the predetermined clock signal CLK. The flip flop circuit  423  outputs the signal Q 3  to be the pseudo random number Q 4  according to the predetermined clock signal CLK. In some embodiments, the signal REF 1  is a predetermined value. 
     The above arrangements about the switched-capacitor circuit Cex8 and/or the pseudo random number generator circuit  160  are given for illustrative purposes, and the present disclosure is not limited thereto. Various types of the switched-capacitor circuit Cex8 and/or the pseudo random number generator circuit  160  are within the contemplated scope of the present disclosure. 
       FIG.  5    is a schematic diagram showing waveforms of the clock signal Φ S1 , the clock signal Φ S2 , and the predetermined clock signal CLK in  FIG.  1    according to some embodiments of the present disclosure. During an interval of the clock signal Φ S1  being at a high level, the capacitor array circuit CT 1  samples the input signal V in . During an interval of the clock signal Φ S2  being at the high level, the capacitor array circuit CT 2  samples the input signal V in . During an interval of the predetermined clock signal CLK being at a high level, the pseudo random number generator circuit  160  outputs the pseudo random number Q 4 . As shown in  FIG.  5   , when the clock signal Φ S1  or the clock signal Φ S2  has the high level, the predetermined clock signal CLK has the high level. In other words, when each of the capacitor array circuits CT 1  and CT 2  samples the input signal V in , the pseudo random number generator circuit  160  outputs the pseudo random number Q 4 . 
       FIG.  6    is a flow chart of a signal conversion method  600  according to some embodiments of the present disclosure. In operation S 610 , an input signal is alternately sampled by capacitor array circuits, in order to generate a sampled input signal. In operation S 620 , an analog to digital conversion is performed according the sampled input signal and a residue signal, in order to generate at least one digital output. In operation S 630 , at least one first circuit in switched-capacitor circuits is utilized to transfer the residue signal from a first capacitor array circuit in capacitor array circuits. In operation S 640 , at least one second circuit is randomly selected from the switched-capacitor circuits to cooperate with a second capacitor array circuit in the capacitor array circuits to sample the input signal. 
     The above operations can be understood with reference to the above embodiments, and thus the repetitious descriptions are not further given. The above description of the signal conversion method  600  includes exemplary operations, but the operations are not necessarily performed in the order described above. Operations of the signal conversion method  600  may be added, replaced, changed order, and/or eliminated as appropriate, or the operations are able to be executed simultaneously or partially simultaneously as appropriate, in accordance with the spirit and scope of various embodiments of the present disclosure. 
     As described above, the time-interleaved ADC and the signal conversion method in some embodiments of the present disclosure are able to randomly select a capacitor to perform the noise shaping function, in order to lower impacts from mismatches in the capacitors. 
     Various functional components or blocks have been described herein. As will be appreciated by persons skilled in the art, in some embodiments, the functional blocks will preferably be implemented through circuits (either dedicated circuits, or general purpose circuits, which operate under the control of one or more processors and coded instructions), which will typically comprise transistors or other circuit elements that are configured in such a way as to control the operation of the circuitry in accordance with the functions and operations described herein. As will be further appreciated, the specific structure or interconnections of the circuit elements will typically be determined by a compiler, such as a register transfer language (RTL) compiler. RTL compilers operate upon scripts that closely resemble assembly language code, to compile the script into a form that is used for the layout or fabrication of the ultimate circuitry. Indeed, RTL is well known for its role and use in the facilitation of the design process of electronic and digital systems. 
     The aforementioned descriptions represent merely some embodiments of the present disclosure, without any intention to limit the scope of the present disclosure thereto. Various equivalent changes, alterations, or modifications based on the claims of present disclosure are all consequently viewed as being embraced by the scope of the present disclosure.