Abstract:
An analog to digital converter (ADC) converts an analog signal to a digital signal. The ADC includes an input channel, a sampling circuit coupled to the input channel, an integrator coupled to the sampling circuit, and a feedback circuit coupled to the integrator. The input channel receives the analog signal. The sampling circuit samples the analog signal. The integrator receives the sampled analog signal and a feedback signal and integrates a superposition of the sampled analog signal and the feedback signal. The feedback circuit generates the digital signal according to an output of the integrator and sends the feedback signal indicative of the digital signal to the integrator.

Description:
RELATED APPLICATION 
       [0001]    This application claims priority to U.S. provisional application, titled “Multi-channel Analog to Digital Converters”, Ser. No. 61/063,744, filed on Feb. 6, 2008, which is incorporated herein by reference in its entirety. 
     
    
     BACKGROUND 
       [0002]    In data acquisition application fields, sometimes multiple analog signals are captured and converted to digital signals over a given time frame simultaneously or parallelly. 
         [0003]    In one of the conventional architectures, a sample/hold block is employed for each input channel. All analog signals from the input channels are sampled simultaneously and then enter hold states. During the hold time period, an analog to digital converter (ADC) can be used to convert the sampled analog values to digital signals sequentially until the sampled signals from all the input channels are converted to digital signals. Some drawbacks exist in this architecture. For instance, multiple sample/hold blocks may be required for multiple channels and the sample/hold blocks can be sensitive to high frequency noises without low-pass filtering capabilities. 
         [0004]    In another conventional architecture, each input channel employs an individual ADC. Therefore, multiple ADCs are required in a data acquisition system with multiple input channels. Averaging-type ADCs can be used in this architecture to implement synchronization among multiple input channels. However, power consumption, die area and cost of the data acquisition system can be increased if multiple ADCs are employed. In addition, different ADCs may cause mismatch among multiple input channels. 
       SUMMARY 
       [0005]    An analog to digital converter (ADC) converts an analog signal to a digital signal. The ADC includes an input channel, a sampling circuit coupled to the input channel, an integrator coupled to the sampling circuit, and a feedback circuit coupled to the integrator. The input channel receives the analog signal. The sampling circuit samples the analog signal. The integrator receives the sampled analog signal and a feedback signal and integrates a superposition of the sampled analog signal and the feedback signal. The feedback circuit generates the digital signal according to an output of the integrator and sends the feedback signal indicative of the digital signal to the integrator. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]    Advantages of the present invention will be apparent from the following detailed description of exemplary embodiments thereof, which description should be considered in conjunction with the accompanying drawings, in which: 
           [0007]      FIG. 1  illustrates a block diagram of a multi-channel analog to digital converter (ADC), in accordance with one embodiment of the present invention. 
           [0008]      FIG. 2  illustrates a timing diagram of signals generated by a multi-channel ADC, in accordance with one embodiment of the invention. 
           [0009]      FIG. 3  illustrates a flowchart of operations performed by a multi-channel ADC, in accordance with one embodiment of the present invention. 
           [0010]      FIG. 4  illustrates a block diagram of an electronic system, in accordance with one embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0011]    Reference will now be made in detail to the embodiments of the present invention, examples of which are illustrated in the accompanying drawings. While the invention will be described in conjunction with the embodiments, it will be understood that they are not intended to limit the invention to these embodiments. On the contrary, the invention is intended to cover alternatives, modifications and equivalents, which may be included within the spirit and scope of the invention as defined by the appended claims. Furthermore, in the following detailed description of embodiments of the present invention, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be recognized by one of ordinary skill in the art that the present invention may be practiced without these specific details. In other instances, well-known methods, procedures, components, and circuits have not been described in detail as not to unnecessarily obscure aspects of the embodiments of the present invention. 
         [0012]    Embodiments described herein may be discussed in the general context of computer-executable instructions residing on some form of computer-usable medium, such as program modules, executed by one or more computers or other devices. Generally, program modules include routines, programs, objects, components, data structures, etc., that perform particular tasks or implement particular abstract data types. The functionality of the program modules may be combined or distributed as desired in various embodiments. 
         [0013]    By way of example, and not limitation, computer-usable media may comprise computer storage media and communication media. Computer storage media includes volatile and nonvolatile, removable and non-removable media implemented in any method or technology for storage of information such as computer-readable instructions, data structures, program modules or other data. Computer storage media includes, but is not limited to, random access memory (RAM), read only memory (ROM), electrically erasable programmable ROM (EEPROM), flash memory or other memory technology, compact disk ROM (CD-ROM), digital versatile disks (DVDs) or other optical storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to store the desired information. 
         [0014]    A multi-channel analog to digital converter (ADC) can convert multiple analog signals from multiple input channels to multiple digital output signals, e.g., multiple analog voltages to multiple digital output voltages, in an interleaved mode. The multi-channel ADC can be used in various data processing applications, such as video systems, audio systems, signal sensors, etc., which may require analog to digital conversions. 
         [0015]      FIG. 1  illustrates a block diagram of an ADC, e.g., a multi-channel ADC  100 , in accordance with one embodiment of the present invention. The multi-channel ADC  100  can be a first-order delta-sigma ADC, in one embodiment. 
         [0016]    The multi-channel ADC  100  can have multiple input channels, e.g., four input channels including channel  1 , channel  2 , channel  3 , and channel  4  for converting analog signals, e.g., analog voltage signals V 1 , V 2 , V 3  and V 4  respectively to digital signals in an interleaved mode, in one embodiment. Each input channel is coupled to an associated switch, e.g., S 1A  associated with channel  1 , S 2A  associated with channel  2 , S 3A  associated with channel  3 , and S 4A  associated with channel  4 . The switches S 1A , S 2A , S 3A , and S 4A  can be controlled by a system clock signal S CLK , in one embodiment. In one embodiment, one input channel is selected during a clock cycle according to the system clock signal S CLK . The switch associated with the selected input channel is turned on and other switches are turned off in one clock cycle, in one embodiment. 
         [0017]    The multi-channel ADC  100  includes a modulator  110  for converting analog signals (e.g., the analog voltage signals V 1 , V 2 , V 3  or V 4 ) to digital signals. The modulator  110  can be a first-order delta-sigma modulator, or a second-order modulator, etc., according to different application requirements. 
         [0018]    The modulator  110  can receive an analog signal from a selected input channel and provide a corresponding digital signal to a filter (e.g., a digital filter F 1 , F 2 , F 3 , or F 4 ) associated with the input channel. The analog signal can be various types of signals, e.g., current or voltage signals. 
         [0019]    The modulator  110  can sample the received analog signal at a predetermined sampling frequency, e.g., a frequency equal to FS*OSR, where Fs is a Nyquist frequency and OSR is an over sampling ratio to the Nyquist frequency. For example, the sampling frequency is 65536 Hz when Fs is 16 Hz and OSR is 4096. The analog signal can be translated to a digital signal at the sampling frequency by the modulator  110 . In one embodiment, the digital signal can be a continuous 1-bit data stream including logic 1 and logic 0 at a rate determined by the sampling frequency (e.g., Fs*OSR). 
         [0020]    In one embodiment, the modulator  110  includes a sampling circuit  130  for sampling the analog signal. The sampling circuit  130  can include an energy storage unit (e.g., sampling capacitor)  120  coupled to the selected input channel for storing charges from the selected input channel, and can include a switch array including switches  122 ,  124 ,  126 , and  128  for controlling the energy storage unit  120 . Switches  122  and  124  are controlled by a signal PH 2 , and switches  126  and  128  are controlled by a signal PH 1 . The signals PH 1  and PH 2  are non-overlapping clock signals, in one embodiment. For example, when the signal PH 2  is at a high level and the signal PH 1  is at a low level, switches  122  and  124  can be turned on and switches  126  and  128  can be turned off. When the signal PH 1  is at a high level and the signal PH 2  is at a low level, switches  122  and  124  can be turned off and switches  126  and  128  can be turned on. 
         [0021]    The modulator  110  can further include an integrator  150  coupled to the sampling circuit  130  for receiving the sampled analog signal and a feedback signal  111  and for integrating a superposition of the sampled analog signal and the feedback signal  111  and generating an output. In the example of  FIG. 1 , the integrator  150  includes a group of integrating capacitors (e.g., integrating capacitors C i1 , C i2 , C i3 , and C i4 ) and an error amplifier  102 . 
         [0022]    The integrating capacitors C i1 , C i2 , C i3 , and C i4  are coupled in parallel. The integrating capacitors C i1 , C i2 , C i3 , and C i4  can accumulate charges from channel  1 , channel  2 , channel  3 , and channel  4  respectively. Each integrating capacitor C i1 , C i2 , C i3 , or C i4  can be coupled to a switch in series, e.g., the integrating capacitor C i1  is coupled to a switch S iB , the integrating capacitor C i2  is coupled to a switch S 2B , the integrating capacitor C i3  is coupled to a switch S 3B , and the integrating capacitor C i4  is coupled to a switch S 4B . 
         [0023]    In one embodiment, the modulator  110  can complete an analog to digital conversion for each input channel sequentially during a conversion cycle. In one embodiment, the integrating capacitors can be randomly allocated to the input channels at the beginning of a conversion cycle. For example, the integrating capacitor C i1  can store charges from channel  2 , the integrating capacitor C i2  can store charges from channel  3 , the integrating capacitor C i3  can store charges from channel  4 , and the integrating capacitor C 41  can store charges from channel  1 , etc. The flexible configuration of the input channels and the integrating capacitors can reduce mismatch between different channels caused by mismatch of the integrating capacitors. In one embodiment, the output of the integrator  150  can include the previous charges stored in a corresponding integrating capacitor during a previous conversion cycle and an integration result of the superposition of the sampled analog signal and the feedback signal  111 . 
         [0024]    In one embodiment, the error amplifier  102  has two input terminals (e.g., an inverting input terminal and a non-inverting input terminal) and an output terminal. The error amplifier  102  can receive an input signal through the inverting input terminal and a first reference signal through the non-inverting input terminal. In one embodiment, the input signal can be a superposition of the sampled analog signal of an input channel and the feedback signal  111 . In one embodiment, the non-inverting input terminal is connected to ground such that a voltage level of the first reference signal is substantially equal to zero. The error amplifier  102  can generate an error signal according to a difference between the input signal (e.g., the superposition of the sampled analog signal and the feedback signal  111 ) and the first reference signal. In one embodiment, the error signal is a voltage signal. 
         [0025]    The modulator  110  further includes a feedback circuit for generating a digital signal according to an output of the integrator  150  and for sending the feedback signal  111  indicative of the digital signal to the integrator  150 . In the example of  FIG. 1 , the feedback circuit can include a comparator  104 , a multiplexer  108 , and a digital to analog converter (DAC)  106 . In other words, the integrator  150 , the comparator  104 , the multiplexer  108 , and the DAC  106  together form a feedback loop. The feedback loop includes a feed forward path including the integrator  150 , the comparator  104  and the multiplexer  108 , and a feed backward path including the DAC  106 . 
         [0026]    The comparator  104  coupled to the integrator  150  can compare the output of the integrator  150  with a second reference signal and for generating a comparator output signal according to the comparison result. In one embodiment, the output of the integrator  150  can include the previous charges stored in a corresponding integrating capacitor during a previous conversion cycle and an integration result of the superposition of the sampled analog signal and the feedback signal  111 . 
         [0027]    The comparator  104  can be controlled by the signal PH 2  and can operate when the signal PH 2  is at a high level. In one embodiment, a non-inverting terminal of the comparator  104  is connected to ground. Thus, a voltage level of the second reference signal is substantially zero. The comparator  104  can generate a 1-bit digital signal (e.g., logic 1 or logic 0) according to the comparison result. The comparator output signal, e.g., a 1-bit digital signal, is further sent to the multiplexer  108 . 
         [0028]    In one embodiment, the multiplexer  108  can be a barrel shift register controlled by a system clock signal S CLK . The multiplexer  108  can pass the digital signal from the comparator  104 , e.g., a 1-bit digital signal, to an output channel, e.g., a digital filter associated with the selected input channel according to the system clock signal S CLK . The output channels can include digital filters F 1 , F 2 , F 3 , and F 4 , such as decimation filters to decimate the digital signals (e.g., the 1-bit digital signals from the comparator  104 ) to multi-bit digital output signals. Therefore, multiple digital output signals associated with the multiple input channels can be obtained from the digital filters (e.g., F 1 , F 2 , F 3 , and F 4 ), respectively. 
         [0029]    Additionally, the multiplexer  108  can latch the 1-bit digital signal from the comparator  104  associated with each input channel. Consequently, during a current conversion cycle, the 1-bit digital signal of each input channel generated in a previous conversion cycle is latched in the multiplexer  108  until a new 1-bit digital signal is generated. When one input channel is selected according to the system clock signal S CLK  in the current conversion cycle, the multiplexer  108  can transfer the 1-bit digital signal of the selected input channel which is generated in a previous conversion cycle to the DAC  106 . During the first conversion cycle, the multiplexer  108  can transfer a 1-bit digital, e.g., logic 0 to the DAC  106 , in one embodiment. 
         [0030]    The DAC  106  can be a 1-bit digital to analog converter, in one embodiment. The DAC  106  can receive the 1-bit digital signal from the multiplexer  108  and convert the 1-bit digital signal to an analog signal (e.g., a voltage signal) according to a reference voltage V REF . The analog signal generated by the DAC  106  can be used as the feedback signal  111  sent to the integrator  150 . The DAC  106  can set the feedback signal  111  equal to −V REF  when the 1-bit digital signal is logic 1 and equal to V REF  when the 1-bit digital signal is logic 0, in one embodiment. The DAC  106  can be controlled by signals PH 1  and PH 2 . Thus, the value of the feedback signal  111  can be set according to the 1-bit digital signal from the multiplexer  108 . 
         [0031]    More specifically, when channel  1  is selected according to the system clock signal S CLK  in a clock cycle during a current conversion cycle, the modulator  110  can receive the analog signal from channel  1  (e.g., the analog voltage signal V 1 ) and a feedback signal  111  from the DAC  106 , and generate a 1-bit digital signal. In one embodiment, the feedback signal  111  from the DAC  106  is generated according to a 1-bit digital signal of channel  1  generated in a previous conversion cycle and according to a reference voltage V REF . The comparator  104  can generate a 1-bit digital signal to the multiplexer  108 . As such, the previous 1-bit digital signal in the multiplexer  108  associated with channel  1  can be replaced by the new 1-bit digital signal generated in the current conversion cycle. The multiplexer  108  can output the 1-bit digital signal generated in the current conversion cycle to the corresponding digital filter F 1 . A next input channel, e.g., channel  2 , can be selected during a next clock cycle of the system clock signal S CLK  and a corresponding 1-bit digital signal can be received by an associated filter. For example, channel  1 , channel  2 , channel  3 , and channel  4  are selected sequentially and 1-bit digital signals corresponding to channel  1 , channel  2 , channel  3 , and channel  4  can be received by the digital filter F 1 , the digital filter F 2 , the digital filter F 3 , and the digital filter F 4  sequentially. The digital filters (e.g., F 1 , F 2 , F 3 , and F 4 ) can accumulate the 1-bit digital signals for several conversion cycles for corresponding input channels and then can generate multi-bit digital output signals. 
         [0032]    Although  FIG. 1  shows a multi-channel analog to digital converter  100 , the invention is not so limited. For example, the modulator  110  can also be used in a single channel analog to digital converter. 
         [0033]    Operations of the multi-channel ADC  100  will be described herein with reference to a timing diagram in  FIG. 2  as an example.  FIG. 2  illustrates waveforms of the system clock signal S CLK , states of the switches S 1A , S 2A , S 3A , S 4A , S 1B , S 2B , S 3B , and S 4B , and the signal PH 2  and the signal PH 1  during operations of the multi-channel ADC  100 , in one embodiment.  FIG. 2  is only for illustrative purposes, and the present invention is not limited to the operation shown in  FIG. 2 . In the example of  FIG. 2 , a switch is turned on when a corresponding state waveform is at a high level and the switch is turned off when the corresponding state waveform is at a low level. 
         [0034]    In the example of  FIG. 2 , a clock cycle of the system clock signal S CLK  is divided into two phases including phase S 1  when the system clock signal S CLK  is at a low level and phase S 2  when the system clock signal S CLK  is at a high level. For instance, each clock cycle, e.g., T 1 , T 2 , T 3 , T 4 , T 5 , etc., includes phase S 1  and phase S 2 . The signal PH 1  is set to a high level and the signal PH 2  is set to a low level during phase S 1  of each clock cycle. Similarly, the signal PH 1  is set to a low level and the signal PH 2  is set to a high level during phase S 2  of each clock cycle. Because the signal PH 1  and the signal PH 2  are non-overlapping clock signals, widths of pulses of the signal PH 1  and the signal PH 2  can be smaller than the widths of the pulses of the system clock signal S LCK  to avoid overlapping, in one embodiment. 
         [0035]    In one embodiment, channel  1  is first selected after the multi-channel ADC  100  is powered on during the clock cycle T 1 . The switches S 1A  and S 1B  associated with channel  1  are turned on and switches associated with other input channels (e.g., channel  2 , channel  3 , and channel  4 ) are turned off. In one embodiment, the switch S 1B  is turned on after a delay of half of a clock cycle, e.g., the switch S 1A  is turned on during the clock cycle T 1  and the switch S 1B  is turned on during phase S 2  of the clock cycle T 1  and phase S 1  of the clock cycle T 2 . The switches  122  and  124  are turned on during phase S 2  of the clock cycle T 1  according to a high level of the signal PH 2 . Simultaneously, the switches  126  and  128  are turned off according to a low level of the signal PH 1  during phase S 2  of the clock cycle T 1 . Therefore, the analog signal from channel  1  (e.g., the analog voltage signal V 1 ) can be transferred to the sampling capacitor  120  via the closed switches S 1A ,  124  and  122 , and can be sampled. Charges from channel  1  corresponding to the analog voltage signal V 1  can be stored in the sampling capacitor  120 . 
         [0036]    During phase S 1  of the clock cycle T 2 , the switches  122  and  124  are turned off according to a low level of the signal PH 2 , and the switches  126  and  128  are turned on according to a high level of the signal PH 1 . Consequently, the charges stored in the sampling capacitor  120  can be transferred to the integrating capacitor C i1  via the closed switches  126 ,  128  and S 1B . 
         [0037]    Additionally, the DAC  106  generates a feedback signal  111  to the integrator  150  according to a 1-bit digital signal of channel  1  in a previous conversion cycle. The output of the integrator  150  can be compared with the second reference signal by the comparator  104  when the signal PH 2  is at a high level during phase S 2  of the clock cycle T 2 . A 1-bit digital signal of channel  1  can be generated by the comparator  104  and be latched in the multiplexer  108 . The digital filter F 1  can receive the 1-bit digital signal. 
         [0038]    Channel  2  is selected during the clock cycle T 2 . The operating sequence associated with channel  2  is similar to the operating sequence associated with channel  1 . Switches S 2A ,  122 , and  124  are turned on and the switches  126  and  128  are turned off according to a high level of the signal PH 2  during phase S 2  of the clock cycle T 2 . An analog signal of channel  2  (e.g., an analog voltage signal V 2 ) can be transferred to the sampling capacitor  120  and be sampled. During phase S 1  of the clock cycle T 3 , the switches  122  and  124  are turned off and the switches  126  and  128  are turned on according to a high level of the signal PH 1 . Because the switch S 1B  is turned off after phase S 1  of the clock cycle T 2  and the switch S 2B  is turned on during phase S 2  of the clock cycle T 2  and phase S 1  of the clock cycle T 3 , charges stored in the sampling capacitor  120  can be transferred to the integrating capacitor C i2  during phase S 1  of the clock cycle T 3 . Then, the comparator  104  can operate during phase S 2  of the clock cycle T 3  and generate a 1-bit digital signal of channel  2  to the multiplexer  108 . The digital filter F 2  can receive the 1-bit digital signal. 
         [0039]    Similarly, channel  3  can be selected during the clock cycle T 3  and can generate a 1-bit digital signal during phase S 2  of the clock cycle T 4 . Channel  4  can be selected during the clock cycle T 4  and can generate a 1-bit digital signal during phase S 2  of the clock cycle T 5 . If more input channels are available, the input channels can be selected sequentially during sequential clock cycles. Thus, the analog signals from the input channels can be converted to digital signals sequentially and circularly. For example, if four input channels exist, at least four clock cycles (e.g., T 1 , T 2 , T 3 , and T 4 ) can be used to accomplish one conversion cycle for all the input channels. The digital filters (e.g., F 1 , F 2 , F 3 , or F 4 ) can receive the 1-bit digital signals for the associated input channels (e.g., channel  1 , channel  2 , channel  3 , or channel  4 ) during each conversion cycle. Then a next conversion cycle starts from the clock cycle T 5 . Similarly, each input channel is selected sequentially and each analog signal is sampled sequentially. Consequently, each digital filter can accumulate the 1-bit digital signals of the associated input channel during multiple conversion cycles and decimate the 1-bit digital signals to generate a multi-bit digital output signal at a predetermined rate, e.g., Fs. 
         [0040]    Assume that the over sampling ratio is OSR, then the time required for a conversion cycle is N*OSR clocks, where N represents the total number of channels, in one embodiment. Advantageously, in one conversion cycle, the analog signals from the input channels can be sampled and converted to 1-bit digital signals respectively and sequentially, in one embodiment. Thus, multi-bit digital output signals of the multiple input channels can be obtained during multiple conversion cycles in a synchronized way. As a result, the multi-channel ADC  100  has an improved efficiency and reduced power consumption, in one embodiment. 
         [0041]    Additionally, in order to speed up the conversions, double sampling technique can be used by adding another switch array (e.g., similar to the switches  122 ,  124 ,  126  and  128 ) and a sampling capacitor (e.g., similar to the sampling capacitor  120 ) with complementary control clock signals (e.g., PH 1  and PH 2 ). In this topology, the speed of the ADC conversion can be doubled without increasing static power consumption. Other sampling techniques, e.g., triple sampling technique can also be used to further speed up the conversions of the ADC  100 . 
         [0042]      FIG. 3  illustrates a flowchart  300  of operations performed by an ADC, e.g., the multi-channel ADC, in accordance with one embodiment of the present invention. Descriptions of  FIG. 3  will be made in combination with  FIG. 1 . One input channel (e.g., channel  1 , channel  2 , channel  3 , or channel  4 ) is selected to receive an analog signal by the multi-channel ADC  100  during a clock cycle of the system clock signal S CLK . In block  310 , the analog signal from the selected input channel is sampled by a sampling circuit  130  during the same clock cycle under the control of a switch array. In block  320 , charges from the sampling capacitor  120  can be transferred to one of the integrating capacitors (e.g., C i1 , C i2 , C i3  or C i4 ) under the control of an associate switch (e.g., S 1B , S 2B , S 3B , or S 4B ). The integrator  150  can integrate a superposition of the sampled analog signal and a feedback signal. The integrating capacitors can be randomly allocated to the input channels at the beginning of a conversion cycle. Advantageously, the flexible configuration of the input channels and the integrating capacitors can reduce mismatch among different channels caused by mismatch of the integrating capacitors. 
         [0043]    In block  330 , a comparator (e.g., the comparator  104 ) can generate a 1-bit digital signal according to an integration result of the superposition. More specifically, the comparator  104  can compare an integrator output with a reference signal (e.g., the voltage level zero) to generate the 1-bit digital signal, and can send the 1-bit digital signal to the multiplexer  108 . The integrator output is generated according to previous charges stored in the corresponding integrating capacitor and according to an integration result of the sampled analog signal and the feedback signal. In block  340 , the multiplexer  108  can output the 1-bit digital signal to the DAC  106  and a corresponding digital filter (e.g., F 1 , F 2 , F 3 , or F 4 ). Hence, the feedback signal  111  can be provided to indicate the 1-bit digital signal. In block  350 , the corresponding digital filter can generate a multi-bit digital output signal according to the 1-bit digital signal. More specifically, the corresponding digital filter can accumulate the 1-bit digital signals for several conversion cycles for a corresponding input channel and then can generate the multi-bit digital output signal. 
         [0044]    Advantageously, multiple input channels can be selected sequentially and corresponding analog signals thereof can be sampled in block  310 . Similarly, the analog signals from other input channels can be converted to digital output signals sequentially via block  310  to block  340 . Advantageously, the traditional sample/hold blocks in the multiple input channels due to synchronization sampling can be avoided such that the whole cost of the circuitry can be reduced. 
         [0045]      FIG. 4  illustrates a block diagram of an electronic system  400 , in accordance with one embodiment of the present invention. The electronic system  400  employs the multi-channel ADC  100  disclosed hereinabove, in one embodiment. The multi-channel ADC  100  has multiple input channels (e.g., channel  1 , channel  2 , channel  3 , . . . , channel N) for receiving analog signals from multiple devices (e.g., devices  402 ,  404 ,  406 , . . . ,  408 ), and for converting the analog signals to digital output signals (e.g., output  1 , output  2 , output  3 , . . . , output N) respectively. The digital output signals can be received by various receivers (e.g., receivers  422 ,  424 ,  426 , . . . ,  428 ). The multi-channel ADC  100  includes a modulator, e.g., the modulator  110 , for converting the analog signals to 1-bit digital signals, and multiple digital filters, e.g., F 1 , F 2 , F 3 , and F 4 , for generating multi-bit digital output signals according to the 1-bit digital signals. The multiple devices (e.g., the devices  402 ,  404 ,  406 , . . . ,  408 ) can be various types of devices, e.g., audio systems, video systems, etc., which can generate analog signals. The receivers (e.g., the receivers  422 ,  424 ,  426 , . . . ,  428 ) can be various types of devices which can receive digital signals. For example, the multi-channel ADC  100  can be used for converting analog voltage monitoring signals indicating battery/cell voltages to digital signals. A battery management system can receive the digital signals and control the battery. 
         [0046]    Accordingly, an ADC (e.g., the multi-channel ADC)  100  for converting an analog signal to a digital signal can include multiple input channels (e.g., channel  1 , channel  2 , channel  3 , channel  4 , etc.), a sampling circuit  130  coupled to the multiple input channels, an integrator  150  coupled to the sampling circuit  130 , and a feedback circuit coupled to the integrator  150 , in one embodiment. The multiple input channels can receive an analog signal when the associated switch is turned on. The sampling circuit  130  includes an energy storage unit  120  for sampling the analog signal from the selected input channel and includes a switch array for controlling the energy storage unit  120 . The integrator  150  can include multiple capacitors (e.g., integrating capacitors) coupled in parallel and an error amplifier  102  coupled to the sampling circuit  130 . The integrating capacitors are coupled to multiple switches respectively. One of the integrating capacitors can store charges from the sampling capacitor  120  when the associate switch is turned on. 
         [0047]    The feedback circuit can include a comparator  104  coupled to the integrator  150 , a multiplexer  108  coupled to the comparator  104 , and a DAC  106  coupled to the sampling circuit  130 . The comparator  104  can compare an output of the integrator  150  with a reference signal (e.g., zero volts) and generate a comparator output signal according to the comparison result. The multiplexer  108  can provide the digital signal according to the comparator output signal. The DAC  106  can generate a feedback signal  111  according to the digital signal. The multi-channel ADC  110  can further include output channels to provide multi-bit digital output signals. 
         [0048]    Advantageously, the multi-channel ADC  100  can perform analog to digital conversions for the multiple input channels in a synchronized and interleaved mode. Multiple sample/hold blocks or multiple ADCs are not required for converting analog signals from multiple input channels, in one embodiment. Hence, the cost of the circuitry can be reduced and the efficiency of the circuitry can be improved. Additionally, the mismatch between multiple ADCs can be reduced/avoided. 
         [0049]    The aforementioned embodiments can also be used in a single channel ADC, when one integrating capacitor and an associated switch coupled in series are included in the integrator  150  and one input channel and one digital filter are included in  FIG. 1 . 
         [0050]    The embodiments that have been described herein, however, are some of the several that utilize this invention and are set forth here by way of illustration but not of limitation. It is obvious that many other embodiments, which will be readily apparent to those skilled in the art, may be made without departing materially from the spirit and scope of the invention as defined in the appended claims. Furthermore, although elements of the invention may be described or claimed in the singular, the plural is contemplated unless limitation to the singular is explicitly stated.