Multi-channel sampling circuit and method and analog-to-digital converter

Abstract

The embodiment of the invention provides a multi-channel sampling circuit and method and an analog-to-digital converter, and the circuit comprises a capacitor, a control module, and a first switch of a first channel, a first switch of a second channel and a voltage output module which are connected with the control module, the control module is used for controlling the first switch of the first channel to be switched on, controlling the first end of the first switch to be connected with the input source of the first channel, controlling the first switch of the second channel to be switched off and controlling the first end of the first switch of the second channel to be connected with preset stable voltage under the condition that the input source of the first channel is sampled. The preset stable voltage is generated according to the input source of the first channel. According to the circuit provided by the embodiment of the invention, errors caused by sampling switch communication cross leakage are reduced, and the sampling accuracy is improved.

Description

Technical Field

[0001] The embodiments of the present application relate to the field of integrated circuit technology, and in particular to a multi-channel sampling circuit, method and analog-to-digital converter. Background Art

[0002] Sampling circuits are mainly used to convert continuous-time analog signals into discrete-time digital signals for processing and analysis by computers or other digital devices. Multi-channel sampling circuits usually include sampling switches for multiple channels and sampling capacitors shared by multiple channels.

[0003] In the related art, the sampling switch usually adopts a Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET).

[0004] However, in the process of implementing the present application, the inventors found that there are at least the following problems in the prior art: MOS tubes have the problem of channel cross leakage, and when the potential difference between the two ends of the sampling switch is too large, it will affect the accuracy of sampling. Summary of the invention

[0005] Embodiments of the present application provide a multi-channel sampling circuit, method, and analog-to-digital converter to improve sampling accuracy.

[0006] In a first aspect, an embodiment of the present application provides a multi-channel sampling circuit, comprising: a capacitor, a control module, and a first switch of a first channel, a first switch of a second channel, and a voltage output module for outputting a preset stable voltage connected to the control module; wherein a first end of the first switch of the first channel is used to be connected to an input source of the first channel or the preset stable voltage, and a second end is connected to the capacitor; a first end of the first switch of the second channel is used to be connected to an input source of the second channel or the preset stable voltage, and a second end is connected to the capacitor;

[0007] The control module is used to control the first switch of the first channel to be turned on and the first end of the first switch to be connected to the input source of the first channel, control the first switch of the second channel to be turned off, and control the first end of the first switch of the second channel to be connected to the preset stable voltage, so as to clamp the first end of the first switch of the second channel when sampling the input source of the first channel; the preset stable voltage is generated according to the input source of the first channel.

[0008] In a possible design, the control module is specifically used to: when sampling the input source of the first channel, control the first switch of the first channel to be turned on, control the first switch of the second channel to be turned off, and control the first end of the first switch of the first channel and the first end of the first switch of the second channel to be connected to the preset stable voltage, so as to pre-charge the capacitor through the preset stable voltage, and clamp the first end of the first switch of the second channel through the preset stable voltage; the preset stable voltage is generated according to the input source of the first channel, and the charging capacity of the preset stable voltage is greater than the charging capacity of the input source of the first channel;

[0009] The control module is also specifically used to: after pre-charging is completed, control the first end of the first switch of the first channel to become connected to the input source of the first channel through the control module, and control the first end of the first switch of the second channel to continue to maintain connection with the preset stable voltage, so as to correct the voltage formed by the pre-charging of the capacitor through the input source of the first channel, thereby realizing sampling of the input source of the first channel.

[0010] In a possible design, the control module is also used to: while maintaining the input source of the first channel, control the first switch of the first channel to be disconnected, control the first switch of the second channel to be disconnected, and control the first end of the first switch of the first channel and the first end of the first switch of the second channel to be connected to the preset stable voltage.

[0011] In a possible design, the multi-channel sampling circuit further includes: a second switch and a third switch of the first channel connected to the control module, wherein one end of the second switch of the first channel is used to be connected to the input source of the first channel, and the other end is connected to the first end of the first switch of the first channel; one end of the third switch of the first channel is connected to the preset stable voltage, and the other end is connected to the first end of the first switch of the first channel;

[0012] When controlling the first end of the first switch to be connected to the input source of the first channel, the control module is specifically used to control the second switch of the first channel to be turned on.

[0013] In a possible design, the multi-channel sampling circuit further includes: a second switch and a third switch of a second channel connected to the control module, wherein the first end of the first switch controlling the second channel is connected to the preset stable voltage, wherein one end of the second switch of the second channel is used to be connected to an input source of the second channel, and the other end is connected to the first end of the first switch of the second channel; one end of the third switch of the second channel is connected to the preset stable voltage, and the other end is connected to the first end of the first switch of the second channel;

[0014] When controlling the first end of the first switch of the second channel to be connected to the preset stable voltage, the control module is specifically used to: control the third switch of the second channel to be turned on, and control the second switch to be turned off.

[0015] In one possible design, the voltage output module includes a first amplifier;

[0016] The control module is further used to control the non-phase input terminal of the first amplifier to be connected to the input source of the first channel while sampling and / or holding the input source of the first channel; and control the output terminal of the first amplifier to be connected to the inverting input terminal and the first terminal of the first switch of the second channel to generate the preset stable voltage.

[0017] In a possible design, the voltage output module further includes: a fourth switch of the first channel and a fourth switch of the second channel connected to the control module; one end of the fourth switch of the first channel is used to be connected to the input source of the first channel, and the other end is connected to the non-inverting input terminal of the first amplifier; one end of the fourth switch of the second channel is used to be connected to the input source of the second channel, and the other end is connected to the non-inverting input terminal of the first amplifier;

[0018] When controlling the non-inverting input terminal of the first amplifier to be connected to the input source of the first channel, the control module is specifically used to: control the fourth switch of the first channel to be turned on, and control the fourth switch of the second channel to be turned off.

[0019] In a second aspect, an embodiment of the present application provides an analog-to-digital converter, comprising: a multi-channel sampling circuit as described in the above-mentioned first aspect and various possible designs of the first aspect.

[0020] In a third aspect, an embodiment of the present application provides a multi-channel sampling method, which is applied to a multi-channel sampling circuit; the multi-channel sampling circuit includes: a capacitor, a control module, and a first switch of a first channel, a first switch of a second channel, and a voltage output module for outputting a preset stable voltage connected to the control module; wherein the first end of the first switch of the first channel is used to be connected to an input source of the first channel or the preset stable voltage, and the second end is connected to the capacitor; the first end of the first switch of the second channel is used to be connected to an input source of the second channel or the preset stable voltage; the second end is connected to the capacitor; the method includes:

[0021] When sampling the input source of the first channel, the control module controls the first switch of the first channel to be turned on, and controls the first end of the first switch of the first channel to be connected to the input source of the first channel, controls the first switch of the second channel to be disconnected, and controls the first end of the first switch of the second channel to be connected to the preset stable voltage, so as to clamp the first end of the first switch of the second channel; the preset stable voltage is generated according to the input source of the first channel.

[0022] In a possible design, controlling the first switch of the first channel to be turned on by the control module, controlling the first end of the first switch of the first channel to be connected to the input source of the first channel, controlling the first switch of the second channel to be turned off, and controlling the first end of the first switch of the second channel to be connected to the preset stable voltage to achieve clamping of the first end of the first switch of the second channel includes:

[0023] Controlling the first switch of the first channel to be turned on and the first switch of the second channel to be turned off by the control module, controlling the first end of the first switch of the first channel and the first end of the first switch of the second channel to be connected to the preset stable voltage, so as to pre-charge the capacitor by the preset stable voltage, and clamp the first end of the first switch of the second channel by the preset stable voltage; the preset stable voltage is generated according to the input source of the first channel, and the charging capacity of the preset stable voltage is greater than the charging capacity of the input source of the first channel;

[0024] After pre-charging is completed, the control module controls the first end of the first switch of the first channel to be connected to the input source of the first channel, and controls the first end of the first switch of the second channel to continue to be connected to the preset stable voltage, so as to correct the voltage formed by the pre-charging of the capacitor through the input source of the first channel, thereby realizing sampling of the input source of the first channel.

[0025] In one possible design, the method further includes:

[0026] While maintaining the input source of the first channel, the control module controls the first switch of the first channel to be disconnected, controls the first switch of the second channel to be disconnected, and controls the first end of the first switch of the first channel and the first end of the first switch of the second channel to be connected to the preset stable voltage.

[0027] The multi-channel sampling circuit, method and analog-to-digital converter provided in the present embodiment include: a capacitor, a control module, and a first switch of the first channel, a first switch of the second channel and a voltage output module for outputting a preset stable voltage connected to the control module, wherein the first end of the first switch of the first channel is used to connect to the input source of the first channel or the preset stable voltage, and the second end is connected to the capacitor, the first end of the first switch of the second channel is used to connect to the input source of the second channel or the preset stable voltage, and the second end is connected to the capacitor, and the control module is used to control the first switch of the first channel to be turned on and the first end of the first switch to be connected to the input source of the first channel, control the first switch of the second channel to be disconnected, and control the first end of the first switch of the second channel to be connected to the preset stable voltage when sampling the input source of the first channel, and the preset stable voltage is generated according to the input source of the first channel. The circuit provided in the embodiment of the present application clamps one end of the switch by the preset stable voltage output by the voltage output module, so that the potential difference between the two ends of the switch is as small as possible, reducing the error introduced by the cross leakage of the sampling switch, and improving the accuracy of sampling. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, a brief introduction will be given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0029] Figure 1 A schematic diagram of a multi-channel sampling circuit provided for related technologies;

[0030] Figure 2 Schematic diagram of the process of the multi-channel sampling method provided in the embodiment of the present application Figure 1 ;

[0031] Figure 3 Schematic diagram of the process of the multi-channel sampling method provided in the embodiment of the present application Figure 2 ;

[0032] Figure 4 A schematic diagram of the structure of the multi-channel sampling circuit provided in the embodiment of the present application Figure 1 ;

[0033] Figure 5 Schematic diagram of the process of the multi-channel sampling method provided in the embodiment of the present application Figure 2 ;

[0034] Figure 6 A schematic diagram of the structure of the multi-channel sampling circuit provided in the embodiment of the present application Figure 2 ;

[0035] Figure 7 Schematic diagram of the switching timing of the multi-channel sampling method provided in the embodiment of the present application Figure 1 ;

[0036] Figure 8 Schematic diagram of the switching timing of the multi-channel sampling method provided in the embodiment of the present application Figure 2 ;

[0037] Fig. 9 A schematic diagram of the structure of the multi-channel sampling circuit provided in the embodiment of the present application Figure 3 . DETAILED DESCRIPTION

[0038] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0039] It should be noted that the multi-channel sampling circuit, method and analog-to-digital converter provided in the present application can be used in the field of integrated circuits, and can also be used in any field other than the field of integrated circuits. The application field of the multi-channel sampling circuit, method and analog-to-digital converter provided in the present application is not limited.

[0040] In applications such as analog-to-digital converters, sampling circuits are essential parts that can sample and hold analog signals for further conversion.

[0041] like Figure 1 As shown in FIG. 1 , the multi-channel sampling circuit is composed of a switch and a sampling capacitor, and its working state is divided into a sampling state and a holding state. The multi-channel sampling circuit shares the same sampling capacitor. For the Nth channel, when it works in the sampling state, the switch S of the Nth channel N When the switch of other channels is turned on, the upper plate of the sampling capacitor is charged by the input source, and its voltage rises to IN N ; When working in the hold state, switch S NDisconnect, the capacitor is in a suspended state, the voltage on the capacitor remains unchanged, and the next conversion begins.

[0042] Generally, the basic unit constituting the switch is an N-type MOS tube or a P-type MOS tube. However, even when the switch is turned off, the MOS tube still has channel cross leakage, which becomes worse as the potential difference between the two ends of the switch increases.

[0043] For example, for Figure 1 In the circuit shown, when the Nth channel is in the sampling state, the voltage on the capacitor is equal to the input source of the Nth channel, and the input sources of other channels are uncertain. In extreme cases, there is a large voltage difference with the Nth channel. The (M-1) switches are connected in parallel and are in the disconnected state. The cross leakage of the channels affects the linear superposition and the accuracy of sampling. When it is in the holding state, the cross leakage of the sampling switch channels continues to affect the accuracy of the holding due to the floating capacitor, and the longer the holding time, the greater the impact on the accuracy.

[0044] In order to solve the above technical problems, the inventors of the present application have found that the essence of the cross leakage of the sampling switch channel is caused by the structural characteristics of the MOS tube, which cannot be avoided; the voltage difference across the sampling switch is determined by the specific conditions when the sampling circuit is working, which is difficult to control. Therefore, ensuring that the potential difference across the switch on the sampling capacitor is as small as possible is the key to significantly reducing the error introduced by the cross leakage of the sampling switch channel. How to ensure that the potential difference across the switch is small? The voltage across the switch can be made the same by clamping. Based on this, the embodiment of the present application provides a multi-channel sampling method.

[0045] The technical solution of the present application is described in detail with specific embodiments below. The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described in detail in some embodiments.

[0046] Figure 2 Schematic diagram of the process of the multi-channel sampling method provided in the embodiment of the present application Figure 1 .like Figure 2 As shown, the method is applied to a multi-channel sampling circuit; the multi-channel sampling circuit comprises: a capacitor, a control module, and a first switch of a first channel, a first switch of a second channel and a voltage output module for outputting a preset stable voltage connected to the control module; wherein the first end of the first switch of the first channel is used to be connected to the input source of the first channel or the preset stable voltage, and the second end is connected to the capacitor; the first end of the first switch of the second channel is used to be connected to the input source of the second channel or the preset stable voltage, and the second end is connected to the capacitor; the method comprises:

[0047] 201. When sampling the input source of the first channel, the control module controls the first switch of the first channel to be turned on, and controls the first end of the first switch of the first channel to be connected to the input source of the first channel, controls the first switch of the second channel to be disconnected, and controls the first end of the first switch of the second channel to be connected to the preset stable voltage, so as to clamp the first end of the first switch of the second channel; the preset stable voltage is generated according to the input source of the first channel.

[0048] In this embodiment, the sampling switches such as the first switch of the first channel and the second switch of the second channel may be P-type MOS tubes or N-type MOS tubes.

[0049] Specifically, the first end of the first switch of each channel is used to connect to a preset stable voltage or a corresponding input source. Figure 3 As shown, the voltage output module 901 generates a preset stable voltage VC, and the first switch (S (M+1)～2M ) can be connected to the preset stable voltage VC or input source (IN 1～M ) connection. It should be noted that the number of preset stable voltages can be one or more. In one achievable manner, in order to simplify the circuit, each channel can share a preset stable voltage. In another achievable manner, considering the load capacity of the preset stable voltage output by the voltage output module, some channels can also share a preset stable voltage. For example, assuming there are 5 channels, the first to third channels can share a preset stable voltage, and the fourth to fifth channels can share a preset stable voltage.

[0050] Wherein, the input of the voltage output module may include an input source of a first channel and an input source of a second channel. When sampling the input source of the first channel, the voltage output module may generate a preset stable voltage according to the input source of the first channel to be connected to the first end of the first switch of the second channel, so that the potential difference between the two ends of the first switch of the second channel in the disconnected state tends to 0 and is reduced as much as possible. When sampling the input source of the second channel, the voltage output module may generate a preset stable voltage according to the input source of the second channel. To be connected to the first end of the first switch of the first channel, so that the potential difference between the two ends of the first switch of the first channel in the disconnected state tends to 0 and is reduced as much as possible.

[0051] In this embodiment, the size of the preset stable voltage is related to the voltage of the input source of the channel to be sampled. For example, when the channel to be sampled is the first channel, the size of the preset stable voltage is related to the voltage of the input source of the first channel. For example, the difference between the preset stable voltage and the voltage of the input source of the first channel can be less than the preset threshold value, or even 0, that is, the preset stable voltage can be equal to the voltage of the input source of the first channel.

[0052] It should be noted that the multi-channel sampling circuit may also include a third channel, a fourth channel, and up to the Nth channel (N is a natural number greater than 4). In the process of sampling a target channel among the multiple channels, the first switch of the target channel is controlled to be turned on, and the first end of the first switch is controlled to be connected to the input source so as to sample the input source of the target channel. For non-target channels, that is, channels other than the target channel to be sampled among the multiple channels, the first switch of the non-target channel is controlled to be turned off. In order to avoid the influence of channel cross leakage after the first switch of the non-target channel is turned off, the first end of the first switch of the non-target channel is connected to a preset stable voltage so that the potential difference across the first switch is small enough to reduce the influence of channel cross leakage.

[0053] The multi-channel sampling method provided in this embodiment clamps one end of the switch through a preset stable voltage output by a voltage output module, so that the potential difference between the two ends of the switch is as small as possible, reducing the error introduced by cross-leakage of the sampling switch and improving the accuracy of sampling.

[0054] In some embodiments, when it is necessary to sample multiple channels simultaneously, multiple multi-channel sampling circuits can be used for sampling. For example, if there are 9 channels, and channels 1, 4, and 7 are sampled in advance, three three-channel sampling circuits can be used, one for channels 1-3, one for channels 4-6, and one for the remaining channels 7-9. Each three-channel sampling circuit includes a first switch for the first channel, the second channel, and the third channel, and also includes a sampling capacitor and a voltage output module. For the specific working process and connection relationship, please refer to the above Figure 2 The embodiments shown will not be described in detail here.

[0055] In some embodiments, the inventors of the present application have discovered that in the process of the input source charging the sampling capacitor, the input source will be affected by the sampling capacitor. The larger the capacitance of the sampling capacitor, the greater the impact. For a multi-channel sampling circuit, the charging capabilities of different input sources are different. The minimum sampling time of the sampling circuit depends on the input source with the minimum charging capability, which limits the sampling efficiency of the sampling circuit. In order to solve this problem, the inventors of the present application have further discovered that a preset stable voltage with a strong charging capability related to the input source can be specially provided to pre-charge the sampling capacitor. When the difference between the voltage charged to the input source is small, the voltage obtained by pre-charging the sampling capacitor through the input source is corrected, thereby improving the sampling efficiency. Based on this, if Figure 3 As shown, based on the above embodiment, for example Figure 2 Based on the illustrated embodiment, step 201 specifically includes:

[0056] 301. Control the first switch of the first channel to be turned on and the first switch of the second channel to be turned off through the control module, and control the first end of the first switch of the first channel and the first end of the first switch of the second channel to be connected to the preset stable voltage, so as to pre-charge the capacitor through the preset stable voltage, and clamp the first end of the first switch of the second channel through the preset stable voltage; the preset stable voltage is generated according to the input source of the first channel, and the charging capacity of the preset stable voltage is greater than the charging capacity of the input source of the first channel.

[0057] 302. After pre-charging is completed, the control module controls the first end of the first switch of the first channel to be connected to the input source of the first channel, and controls the first end of the first switch of the second channel to continue to be connected to the preset stable voltage, so as to correct the voltage formed by the pre-charging of the capacitor through the input source of the first channel, thereby realizing sampling of the input source of the first channel.

[0058] In this embodiment, the sampling switches such as the first switch of the first channel and the second switch of the second channel may be P-type MOS tubes or N-type MOS tubes.

[0059] Specifically, the voltage output module generates a preset stable voltage according to the input source of the channel to be sampled. The voltage difference between the preset stable voltage and the corresponding input source is less than the preset threshold, and the charging capacity of the preset stable voltage is relatively stable, and the charging efficiency is higher than that of directly charging the capacitor by the input source of different channels.

[0060] Specifically, the first end of the first switch of each channel is used to connect to a preset stable voltage or a corresponding input source. Figure 4 As shown, the voltage output module 401 generates a preset stable voltage VC, and the first switch (S (M+1)～2M ) can be connected to the preset stable voltage VC or input source (IN 1～M ) connection. It should be noted that the number of preset stable voltages can be one or more. In one achievable manner, in order to simplify the circuit, each channel can share a preset stable voltage. In another achievable manner, considering the load capacity of the preset stable voltage output by the voltage output module, some channels can also share a preset stable voltage. For example, assuming there are 5 channels, the first to third channels can share a preset stable voltage, and the fourth to fifth channels can share a preset stable voltage.

[0061] Wherein, the input of the voltage output module may include an input source of a first channel and an input source of a second channel. When sampling the input source of the first channel, the voltage output module may generate a preset stable voltage according to the input source of the first channel to be connected to the first end of the first switch of the second channel, so that the potential difference between the two ends of the first switch of the second channel in the disconnected state tends to 0 and is reduced as much as possible. When sampling the input source of the second channel, the voltage output module may generate a preset stable voltage according to the input source of the second channel. To be connected to the first end of the first switch of the first channel, so that the potential difference between the two ends of the first switch of the first channel in the disconnected state tends to 0 and is reduced as much as possible.

[0062] In this embodiment, the size of the preset stable voltage is related to the voltage of the input source of the channel to be sampled. For example, when the channel to be sampled is the first channel, the size of the preset stable voltage is related to the voltage of the input source of the first channel. For example, the difference between the preset stable voltage and the voltage of the input source of the first channel can be less than the preset threshold value, or even 0, that is, the preset stable voltage can be equal to the voltage of the input source of the first channel.

[0063] It should be noted that the multi-channel sampling circuit may also include a third channel, a fourth channel, and up to the Nth channel (N is a natural number greater than 4). In the process of sampling a target channel among the multiple channels, the first switch of the target channel is controlled to be turned on, and the first end of the first switch is controlled to be connected to the input source so as to sample the input source of the target channel. For non-target channels, that is, channels other than the target channel to be sampled among the multiple channels, the first switch of the non-target channel is controlled to be turned off. In order to avoid the influence of channel cross leakage after the first switch of the non-target channel is turned off, the first end of the first switch of the non-target channel is connected to a preset stable voltage so that the potential difference across the first switch is small enough to reduce the influence of channel cross leakage.

[0064] The multi-channel sampling method provided in this embodiment can not only make the potential difference between the two ends of the switch as small as possible through the voltage output module, reduce the error introduced by the cross-leakage of the sampling switch, and improve the accuracy of sampling, but also pre-charge the sampling capacitor through the voltage output module, thereby improving the sampling efficiency.

[0065] In some embodiments, when it is necessary to sample multiple channels simultaneously, multiple multi-channel sampling circuits can be used for sampling. For example, if there are 9 channels, and channels 1, 4, and 7 are sampled in advance, three three-channel sampling circuits can be used, one for channels 1-3, one for channels 4-6, and one for the remaining channels 7-9. Each three-channel sampling circuit includes a first switch for the first channel, the second channel, and the third channel, and also includes a sampling capacitor and a voltage output module. For the specific working process and connection relationship, please refer to the above Figure 3 The embodiments shown will not be described in detail here.

[0066] In some embodiments, Figure 2 On the basis of the embodiment shown, in order to improve the accuracy of the holding stage, during the holding stage, multiple switches with one end connected to the capacitor can have their other ends clamped by the same preset stable voltage to reduce the potential difference across the switches. Figure 5 As shown, after step 201, the following steps may also be included:

[0067] 202. While maintaining the input source of the first channel, the control module controls the first switch of the first channel to be disconnected, controls the first switch of the second channel to be disconnected, and controls the first end of the first switch of the first channel and the first end of the first switch of the second channel to be connected to the preset stable voltage.

[0068] Specifically, after the sampling is completed, the holding phase is entered, and in the holding phase, the first switches of each channel are disconnected. At this time, in order to avoid the first switches of each channel being affected by the cross-channel leakage after being disconnected, the first ends of the first switches of each channel can be connected to a preset stable voltage, so that the potential difference between the two ends of the first switch is small enough to reduce the influence of the cross-channel leakage.

[0069] The multi-channel sampling method provided in this embodiment can make the potential difference between the two ends of the first switch as small as possible by controlling the first end of the first switch of each channel in the disconnected state to be connected to a preset stable voltage during the holding stage, thereby avoiding the influence of channel cross leakage and improving the holding accuracy.

[0070] In some embodiments, the multi-channel sampling circuit further includes: a second switch and a third switch of the first channel connected to the control module, wherein one end of the second switch of the first channel is used to connect to the input source of the first channel, and the other end is connected to the first end of the first switch of the first channel; one end of the third switch of the first channel is connected to the preset stable voltage, and the other end is connected to the first end of the first switch of the first channel; controlling the first end of the first switch of the first channel to be connected to the input source of the first channel may include: controlling the second switch of the first channel to be turned on, and controlling the third switch of the first channel to be turned off.

[0071] Specifically, the preset stable voltage can be connected to the first switch through the third switch, and the input source of the first channel can be connected to the first switch through the second switch. Based on this, if the first channel is sampling, the second switch can be turned on and the third switch can be turned off. If the second channel, or a channel other than the first channel, is sampling, the third switch can be turned on and the second switch can be turned off.

[0072] In some embodiments, the multi-channel sampling circuit further includes: a second switch and a third switch of the second channel connected to the control module, the first end of the first switch controlling the second channel being connected to the preset stable voltage, wherein one end of the second switch of the second channel is used to connect to the input source of the second channel, and the other end is connected to the first end of the first switch of the second channel; one end of the third switch of the second channel is connected to the preset stable voltage, and the other end is connected to the first end of the first switch of the second channel; the control of connecting the first end of the first switch of the second channel to the preset stable voltage may include: controlling the third switch of the second channel to be turned on, and controlling the second switch of the second channel to be turned off.

[0073] Specifically, the preset stable voltage can be connected to the first switch through the third switch, and the input source of the second channel can be connected to the first switch through the second switch. Based on this, if the second channel is sampling, the second switch can be turned on and the third switch can be turned off. If the first channel, or a channel other than the second channel, is sampling, the third switch can be turned on and the second switch can be turned off.

[0074] In some embodiments, the voltage output module includes a first amplifier; the method further includes: when sampling the input source of the first channel, controlling the non-phase input terminal of the first amplifier to be connected to the input source of the first channel through the control module; controlling the output terminal of the first amplifier to be connected to the inverting input terminal and the first end of the first switch of the second channel to generate the preset stable voltage.

[0075] Specifically, the first amplifier can be a voltage amplifier, and the output terminal of the first amplifier is connected to the inverting input terminal to form a voltage follower structure, thereby making the output terminal follow the voltage inputted by the non-inverting input terminal. That is, when the first channel is sampled and held, a preset stable voltage equal to the input source of the first channel can be generated.

[0076] In some embodiments, the voltage output module also includes: a fourth switch of the first channel and a fourth switch of the second channel connected to the control module; one end of the fourth switch of the first channel is used to connect to the input source of the first channel, and the other end is connected to the positive input terminal of the first amplifier; one end of the fourth switch of the second channel is used to connect to the input source of the second channel, and the other end is connected to the positive input terminal of the first amplifier; controlling the positive input terminal of the first amplifier to be connected to the input source of the first channel may include: controlling the fourth switch of the first channel to be turned on, and controlling the fourth switch of the second channel to be turned off.

[0077] In this embodiment, since the preset stable voltages required when the input sources of different channels are sampled may be different, the input source can be selected for the positive input terminal of the first amplifier by turning on and off the fourth switch. When the input source of the Nth channel is sampled, the fourth switch of the Nth channel can be turned on and the fourth switch of the non-Nth channel can be turned off, so that the input source of the Nth channel is input to the positive input terminal of the first amplifier.

[0078] The following combination Figure 6 The multi-channel sampling circuit shown and Figure 7 The switch on and off timing shown Figure 1 , the multi-channel sampling method is explained in detail.

[0079] like Figure 6 As shown, the multi-channel sampling circuit includes: first switches of M channels (M+1 switch, M+2 switch, ..., 2M switch), second switches of M channels (1 switch, 2 switch, ..., M switch), third switches of M channels (2M+1 switch, 2M+2 switch, ..., 3M switch), fourth switches of M channels (3M+1 switch, 3M+2 switch, ..., 4M switch), sampling capacitors and voltage amplifiers. The voltage amplifier AMP and the fourth switches of M channels (3M+1 switch, 3M+2 switch, ..., 4M switch) constitute a voltage output module 901, wherein one end of the M second switches is connected to input sources IN1 to IN2. M , the other end is connected to one end of the M first switches and the M third switches, the other end of the M first switches is connected to the upper plate of the sampling capacitor, the other end of the M third switches is connected to the negative input end of the voltage amplifier, and one end of the M fourth switches is connected to the input source IN1~INM The other end is connected to the positive input of the voltage amplifier, the lower plate of the sampling capacitor is connected to the common mode voltage VCM, and the output and negative input of the voltage amplifier are connected together. The state of each switch depends on which channel is being sampled and the working state of the sampling circuit.

[0080] The channel to be sampled is the first channel. In the specific working process, if Figure 7 As shown, the sampling phase begins at time t1, and switches S1 and S M+1 On, switch S 2M+1 Keep it disconnected, IN1 of the first channel charges the capacitor C, and the switch S 3M+1 On, switch S (2+3M)～4M The input end of the voltage output module is connected to IN1 of the first channel to generate a preset stable voltage related to IN1. The switch S (2+2M)～3M On, switch S 2～M Keep disconnected, and avoid too large a potential difference between the two ends of the switch by presetting a stable voltage. At time t2, the switch S1 and S M+1 Disconnect, switch S after a certain delay 2M+1 The preset stable voltage clamps the switch of the first channel, and the switch S 3M+1 Keep conducting, switch S (2+3M)～4M The input end of the voltage output module is connected to IN1 of the first channel to generate a preset stable voltage related to IN1. The switch S (2+2M)～3M On, switch S 2～M Keep it disconnected and avoid too large a potential difference across the switch from the 2nd channel to the Mth channel by presetting a stable voltage.

[0081] The following combination Figure 6 The multi-channel sampling circuit shown and Figure 8 The switch on and off timing shown Figure 2 , the multi-channel sampling method is explained in detail.

[0082] like Figure 6 As shown, the multi-channel sampling circuit includes: first switches of M channels (M+1 switch, M+2 switch, ..., 2M switch), second switches of M channels (1 switch, 2 switch, ..., M switch), third switches of M channels (2M+1 switch, 2M+2 switch, ..., 3M switch), fourth switches of M channels (3M+1 switch, 3M+2 switch, ..., 4M switch), sampling capacitors and voltage amplifiers. The voltage amplifier AMP and the fourth switches of M channels (3M+1 switch, 3M+2 switch, ..., 4M switch) constitute a voltage output module 401. Among them, one end of the M second switches is connected to the input sources IN1 to IN2. M, the other end is connected to one end of the M first switches and the M third switches, the other end of the M first switches is connected to the upper plate of the sampling capacitor, the other end of the M third switches is connected to the negative input end of the voltage amplifier, and one end of the M fourth switches is connected to the input source IN1~IN M The other end is connected to the positive input of the voltage amplifier, the lower plate of the sampling capacitor is connected to the common mode voltage VCM, and the output and negative input of the voltage amplifier are connected together. The state of each switch depends on which channel is being sampled and the working state of the sampling circuit.

[0083] The channel to be sampled is the first channel. In the specific working process, if Figure 8 As shown, at time t1, the pre-charging phase begins, switch S1 is disconnected, and switch S M+1 On, switch S 2M+1 The preset stable voltage is used to pre-charge the sampling capacitor C, and the switch S 3M+1 Keep conducting, switch S (2+3M)～4M The input end of the voltage output module is connected to IN1 of the first channel to generate a preset stable voltage related to IN1. The switch S (2+2M)～3M On, switch S 2～M Keep it disconnected and avoid too large a potential difference across the switch from the 2nd channel to the Mth channel by presetting a stable voltage.

[0084] At t2, the sampling phase begins and the switch S M+1 Continue to keep conducting, switch S1 is turned on after a delay, and switch S 2M+1 Disconnect, IN1 of the first channel charges capacitor C, switch S 3M+1 Continue to keep on, switch S (2+3M)～4M The input end of the voltage output module is connected to IN1 of the first channel to generate a preset stable voltage related to IN1. The switch S (2+2M)～3M Keep conducting, switch S 2～M Keep it open and avoid too large a potential difference across the switch by presetting a stable voltage.

[0085] At time t3, the holding phase begins and switches S1 and S M+1 Disconnect, switch S after a certain delay 2M+1 The preset stable voltage clamps the switch of the first channel, and the switch S 3M+1 Keep conducting, switch S (2+3M)～4M The input end of the voltage output module is connected to IN1 of the first channel to generate a preset stable voltage related to IN1. The switch S (2+2M)～3M On, switch S 2～M Keep it disconnected and avoid too large a potential difference across the switch from the 2nd channel to the Mth channel by presetting a stable voltage.

[0086] Fig. 9 A schematic diagram of the structure of the multi-channel sampling circuit provided in the embodiment of the present application Figure 3 .like Fig. 9 As shown, the multi-channel sampling circuit includes a capacitor, a control module 902, and a first switch S of a first channel connected to the control module 902. M+1 , the first switch S of the second channel M+2 and a voltage output module 901 for outputting a preset stable voltage VC; wherein the first switch S of the first channel M+1 The first end of the first switch S of the second channel is used to be connected to the input source IN1 of the first channel or the preset stable voltage VC, and the second end is connected to the capacitor; M+2 The first end is used to be connected to the input source IN2 of the second channel or the preset stable voltage VC; the second end is connected to the capacitor;

[0087] The control module 902 is used to control the first switch S of the first channel when sampling the input source IN1 of the first channel. M+1 The first end of the first switch is turned on and connected to the input source IN1 of the first channel, and the first switch S of the second channel is controlled. M+2 disconnect, control the first switch of the second channel SM+2 The first end is connected to the preset stable voltage VC; the preset stable voltage VC is generated according to the input source IN1 of the first channel.

[0088] The multi-channel sampling circuit provided in this embodiment clamps one end of the switch through the preset stable voltage output by the voltage output module, so that the potential difference between the two ends of the switch is as small as possible, reducing the error introduced by the cross leakage of the sampling switch communication and improving the sampling accuracy.

[0089] In some embodiments, the control module 902 is specifically used to: when sampling the input source of the first channel, control the first switch of the first channel to be turned on, control the first switch of the second channel to be turned off, and control the first end of the first switch of the first channel and the first end of the first switch of the second channel to be connected to the preset stable voltage, so as to pre-charge the capacitor through the preset stable voltage, and clamp the first end of the first switch of the second channel through the preset stable voltage; the preset stable voltage is generated according to the input source of the first channel, and the charging capacity of the preset stable voltage is greater than the charging capacity of the input source of the first channel;

[0090] The control module 902 is also specifically used for: after pre-charging is completed, after pre-charging is completed, controlling the first end of the first switch of the first channel to become connected to the input source of the first channel through the control module 902, and controlling the first end of the first switch of the second channel to continue to maintain connection with the preset stable voltage, so as to correct the voltage formed by the pre-charging of the capacitor through the input source of the first channel, thereby realizing sampling of the input source of the first channel.

[0091] In some embodiments, the control module 902 is also used to: while maintaining the input source of the first channel, control the first switch of the first channel to be disconnected, control the first switch of the second channel to be disconnected, and control the first end of the first switch of the first channel and the first end of the first switch of the second channel to be connected to the preset stable voltage.

[0092] In some embodiments, the multi-channel sampling circuit further includes: a second switch and a third switch of the first channel connected to the control module 902, wherein one end of the second switch of the first channel is used to be connected to the input source of the first channel, and the other end is connected to the first end of the first switch of the first channel; one end of the third switch of the first channel is connected to the preset stable voltage, and the other end is connected to the first end of the first switch of the first channel;

[0093] When controlling the first end of the first switch to be connected to the input source of the first channel, the control module 902 is specifically configured to control the second switch of the first channel to be turned on.

[0094] In some embodiments, the multi-channel sampling circuit further includes: a second switch and a third switch of the second channel connected to the control module 902, wherein the first end of the first switch of the second channel is connected to the preset stable voltage, wherein one end of the second switch of the second channel is used to be connected to the input source of the second channel, and the other end is connected to the first end of the first switch of the second channel; one end of the third switch of the second channel is connected to the preset stable voltage, and the other end is connected to the first end of the first switch of the second channel;

[0095] When controlling the first end of the first switch of the second channel to be connected to the preset stable voltage, the control module 902 is specifically used to: control the third switch of the second channel to be turned on, and control the second switch to be turned off.

[0096] In some embodiments, the voltage output module 901 includes a first amplifier;

[0097] The control module 902 is also used to control the non-phase input terminal of the first amplifier to be connected to the input source of the first channel while sampling and / or holding the input source of the first channel; and control the output terminal of the first amplifier to be connected to the inverting input terminal and the first terminal of the first switch of the second channel to generate the preset stable voltage.

[0098] In some embodiments, the voltage output module 901 further includes: a fourth switch of the first channel and a fourth switch of the second channel connected to the control module 902; one end of the fourth switch of the first channel is used to be connected to the input source of the first channel, and the other end is connected to the non-inverting input terminal of the first amplifier; one end of the fourth switch of the second channel is used to be connected to the input source of the second channel, and the other end is connected to the non-inverting input terminal of the first amplifier;

[0099] When controlling the non-inverting input terminal of the first amplifier to be connected to the input source of the first channel, the control module 902 is specifically used to: control the fourth switch of the first channel to be turned on, and control the fourth switch of the second channel to be turned off.

[0100] The multi-channel sampling circuit provided in the embodiment of the present application can be used to execute the above-mentioned method embodiment. Its implementation principle and technical effect are similar, and this embodiment will not be repeated here.

[0101] An embodiment of the present application further provides an analog-to-digital converter, comprising the multi-channel sampling circuit described in the above embodiment.

[0102] The analog-to-digital converter provided in this embodiment sets a voltage output module in the sampling circuit to minimize the potential difference between the two ends of the switch, thereby reducing the error introduced by cross-leakage of the sampling switch and improving the sampling accuracy.

[0103] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A multi-channel sampling circuit, characterized in that: include: A capacitor, a control module, and a first switch of a first channel, a first switch of a second channel connected to the control module, and a voltage output module for outputting a preset stable voltage; wherein a first end of the first switch of the first channel is used to be connected to an input source of the first channel or the preset stable voltage, and a second end is connected to the capacitor; a first end of the first switch of the second channel is used to be connected to an input source of the second channel or the preset stable voltage, and a second end is connected to the capacitor; The control module is used to control the first switch of the first channel to be turned on and the first end of the first switch to be connected to the input source of the first channel, control the first switch of the second channel to be turned off, and control the first end of the first switch of the second channel to be connected to the preset stable voltage, so as to clamp the first end of the first switch of the second channel when sampling the input source of the first channel; the preset stable voltage is generated according to the input source of the first channel.

2. The circuit according to claim 1, characterized in that The control module is specifically used to: when sampling the input source of the first channel, control the first switch of the first channel to be turned on, control the first switch of the second channel to be turned off, and control the first end of the first switch of the first channel and the first end of the first switch of the second channel to be connected to the preset stable voltage, so as to pre-charge the capacitor through the preset stable voltage, and clamp the first end of the first switch of the second channel through the preset stable voltage; the preset stable voltage is generated according to the input source of the first channel, and the charging capacity of the preset stable voltage is greater than the charging capacity of the input source of the first channel; The control module is also specifically used to: after pre-charging is completed, control the first end of the first switch of the first channel to become connected to the input source of the first channel through the control module, and control the first end of the first switch of the second channel to continue to maintain connection with the preset stable voltage, so as to correct the voltage formed by the pre-charging of the capacitor through the input source of the first channel, thereby realizing sampling of the input source of the first channel.

3. The circuit according to claim 1, characterized in that The control module is also used to: while maintaining the input source of the first channel, control the first switch of the first channel to be disconnected, control the first switch of the second channel to be disconnected, and control the first end of the first switch of the first channel and the first end of the first switch of the second channel to be connected to the preset stable voltage.

4. The circuit according to any one of claims 1 to 3, characterized in that: The multi-channel sampling circuit further includes: a second switch and a third switch of the first channel connected to the control module, wherein one end of the second switch of the first channel is used to be connected to the input source of the first channel, and the other end is connected to the first end of the first switch of the first channel; one end of the third switch of the first channel is connected to the preset stable voltage, and the other end is connected to the first end of the first switch of the first channel; When controlling the first end of the first switch to be connected to the input source of the first channel, the control module is specifically used to control the second switch of the first channel to be turned on.

5. The circuit according to claim 4, characterized in that The multi-channel sampling circuit further includes: a second switch and a third switch of the second channel connected to the control module, wherein the first end of the first switch controlling the second channel is connected to the preset stable voltage, wherein one end of the second switch of the second channel is used to be connected to the input source of the second channel, and the other end is connected to the first end of the first switch of the second channel; one end of the third switch of the second channel is connected to the preset stable voltage, and the other end is connected to the first end of the first switch of the second channel; When controlling the first end of the first switch of the second channel to be connected to the preset stable voltage, the control module is specifically used to: control the third switch of the second channel to be turned on, and control the second switch to be turned off.

6. The circuit according to any one of claims 1 to 3, characterized in that: The voltage output module includes a first amplifier; The control module is further used to control the non-phase input terminal of the first amplifier to be connected to the input source of the first channel while sampling and / or holding the input source of the first channel; and control the output terminal of the first amplifier to be connected to the inverting input terminal and the first terminal of the first switch of the second channel to generate the preset stable voltage.

7. The circuit according to claim 6, characterized in that The voltage output module further includes: a fourth switch of the first channel and a fourth switch of the second channel connected to the control module; one end of the fourth switch of the first channel is used to be connected to the input source of the first channel, and the other end is connected to the non-inverting input terminal of the first amplifier; one end of the fourth switch of the second channel is used to be connected to the input source of the second channel, and the other end is connected to the non-inverting input terminal of the first amplifier; When controlling the non-inverting input terminal of the first amplifier to be connected to the input source of the first channel, the control module is specifically used to: control the fourth switch of the first channel to be turned on, and control the fourth switch of the second channel to be turned off.

8. An analog-to-digital converter, characterized in that: It comprises the multi-channel sampling circuit as described in any one of claims 1 to 7.

9. A multi-channel sampling method, characterized in that: Applied to a multi-channel sampling circuit; the multi-channel sampling circuit comprises: a capacitor, a control module, and a first switch of a first channel, a first switch of a second channel connected to the control module, and a voltage output module for outputting a preset stable voltage; wherein the first end of the first switch of the first channel is used to be connected to the input source of the first channel or the preset stable voltage, and the second end is connected to the capacitor; the first end of the first switch of the second channel is used to be connected to the input source of the second channel or the preset stable voltage, and the second end is connected to the capacitor; the method comprises: When sampling the input source of the first channel, the control module controls the first switch of the first channel to be turned on, and controls the first end of the first switch of the first channel to be connected to the input source of the first channel, controls the first switch of the second channel to be disconnected, and controls the first end of the first switch of the second channel to be connected to the preset stable voltage, so as to clamp the first end of the first switch of the second channel; the preset stable voltage is generated according to the input source of the first channel.

10. The method according to claim 9, characterized in that The control module controls the first switch of the first channel to be turned on, controls the first end of the first switch of the first channel to be connected to the input source of the first channel, controls the first switch of the second channel to be turned off, controls the first end of the first switch of the second channel to be connected to the preset stable voltage, and implements clamping of the first end of the first switch of the second channel, including: Controlling the first switch of the first channel to be turned on and the first switch of the second channel to be turned off by the control module, controlling the first end of the first switch of the first channel and the first end of the first switch of the second channel to be connected to the preset stable voltage, so as to pre-charge the capacitor by the preset stable voltage, and clamp the first end of the first switch of the second channel by the preset stable voltage; the preset stable voltage is generated according to the input source of the first channel, and the charging capacity of the preset stable voltage is greater than the charging capacity of the input source of the first channel; After pre-charging is completed, the control module controls the first end of the first switch of the first channel to be connected to the input source of the first channel, and controls the first end of the first switch of the second channel to continue to be connected to the preset stable voltage, so as to correct the voltage formed by the pre-charging of the capacitor through the input source of the first channel, thereby realizing sampling of the input source of the first channel.

11. The method according to claim 9 or 10, characterized in that: The method further comprises: While maintaining the input source of the first channel, the control module controls the first switch of the first channel to be disconnected, controls the first switch of the second channel to be disconnected, and controls the first end of the first switch of the first channel and the first end of the first switch of the second channel to be connected to the preset stable voltage.

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