Analog-to-digital converter driving stage control circuit

Abstract

The invention provides an analog-to-digital converter driving stage control circuit, which comprises an in-phase and out-phase input end, a capacitance coupling closed-loop amplifier, a level lifting capacitance loop and an in-phase and out-phase output end, wherein the non-inverting input end is connected with the input end of the capacitance coupling closed-loop amplifier and the input end of the level lifting capacitance loop; the capacitance coupling closed-loop amplifier is connected in parallel with the level lifting capacitance loop; the non-inverting output end is connected with the analog-to-digital converter; in each period of the analog-to-digital converter, the input voltage of the analog-to-digital converter is adjusted by opening and closing a switch in the level lifting capacitor loop. Related level lifting is carried out on the sampling capacitor of the analog-to-digital converter successively by adopting the level lifting capacitor loop and the sampling period of the analog-to-digital converter, so that the voltage swing output by the amplifier is greatly reduced, the linearity of the output of the amplifier is improved, and the amplifier can be applied to a high-precision signal chain scene.

Description

Technical Field

[0001] The present invention relates to the technical field of analog-to-digital converter driving, and in particular to an analog-to-digital converter driving stage control circuit. Background Art

[0002] In order to realize a high-precision and high-linearity analog-to-digital converter (ADC), a high-performance pre-driver stage is usually required. Specifically, the performance requirements for the pre-driver stage are mainly strong driving capability and high linearity. Usually, the pre-driver stage circuit of the ADC requires a higher power supply voltage than the ADC, so as to ensure that the output tube of the driver stage does not enter the linear region when the ADC is fully input, and meet the high linearity requirements of the ADC. On the other hand, the strong drive and low noise requirements of the ADC driver stage generally require the ADC driver stage to consume a large amount of current, which leads to a huge power consumption overhead of the ADC driver stage.

[0003] The existing ADC driver stage usually adopts the circuit structure of source follower. On this basis, some driver stage circuit technologies that can achieve rail-to-rail high linearity are proposed. Many signal chain application scenarios require the driver stage to provide programmable gain. In this case, the existing source follower circuit structure is no longer applicable. How to use the analog-to-digital converter driver stage control circuit (Programmable Gain Amplifier, PGA) with capacitive coupling closed-loop amplification as the pre-stage driver of the ADC is a solution that needs to be implemented urgently. Summary of the invention

[0004] The present invention provides an analog-to-digital converter driving stage control circuit, which is used to solve the defect that the existing ADC driving stage control circuit cannot provide programmable voltage gain, and realize the programmable voltage gain of the ADC driving stage.

[0005] The present invention provides an analog-to-digital converter driving stage control circuit, comprising in-phase and inverting input terminals, a capacitive coupling closed-loop amplifier, a level-lifting capacitor loop and in-phase and inverting output terminals, wherein: The in-phase and inverting input terminals are connected to the input terminals of the capacitive coupling closed-loop amplifier, and the in-phase and inverting input terminals are also connected to the input terminals of the level-raising capacitor loop; The in-phase and inverting output terminals are connected to the output terminal of the capacitive coupling closed-loop amplifier, and the in-phase and inverting output terminals are also connected to the output terminal of the level-raising capacitor loop; The capacitive coupling closed-loop amplifier is connected in parallel with the level-raising capacitive loop; The in-phase and inverting output terminals are connected to an analog-to-digital converter; During each period of the analog-to-digital converter, the input voltage of the analog-to-digital converter is adjusted by opening and closing the switch in the level-lifting capacitor circuit.

[0006] According to an analog-to-digital converter drive stage control circuit provided by the present invention, the level-lifting capacitor circuit includes a DC servo circuit, a variable-capacitance capacitor, a plurality of capacitor switches, a converter switch, and a level-lifting capacitor, wherein: The DC servo circuit is connected in parallel with the variable-capacitance capacitor, and the DC servo circuit is also connected in parallel with the capacitive coupling closed-loop amplifier; During each period of the analog-to-digital converter, the input voltage of the analog-to-digital converter is adjusted by changing the switch states of the capacitor switch and the converter switch.

[0007] According to an analog-to-digital converter drive stage control circuit provided by the present invention, during each period of the analog-to-digital converter, the capacitive coupling closed-loop amplifier is connected to the non-inverting / inverting output terminal through the converter switch, or the capacitive coupling closed-loop amplifier is connected to the non-inverting / inverting output terminal through the level-lifting capacitor.

[0008] According to an analog-to-digital converter drive stage control circuit provided by the present invention, the DC servo circuit includes a pseudo-resistor and a target amplifier, wherein: The pseudo-resistor is connected to the non-inverting / inverting input terminal, and the pseudo-resistor is also connected to the input terminal of the capacitive coupling closed-loop amplifier; The target amplifier is connected to the output node of the capacitive coupling closed-loop amplifier.

[0009] According to an analog-to-digital converter drive stage control circuit provided by the present invention, during each period of the analog-to-digital converter, the output node is connected to the non-inverting / inverting output terminal through the converter switch, or the output node is connected to the non-inverting / inverting output terminal through the level-lifting capacitor.

[0010] According to an analog-to-digital converter drive stage control circuit provided by the present invention, when the analog-to-digital converter is in the conversion period, the first capacitor switch and the second capacitor switch among the plurality of capacitor switches are disconnected, the third capacitor switch, the fourth capacitor switch, and the converter switch among the plurality of capacitor switches are closed, and the capacitive coupling closed-loop amplifier is connected to the non-inverting / inverting output terminal through the converter switch; The plurality of capacitor switches and the converter switch are disposed between the capacitive coupling closed-loop amplifier and the non-inverting / inverting output terminal; the first capacitor switch and the second capacitor switch are connected in parallel, and the third capacitor switch and the fourth capacitor switch are connected in series.

[0011] According to an ADC driver stage control circuit provided by the present invention, when the ADC is in the first sampling period, the second capacitor switch, the third capacitor switch, and the converter switch are disconnected, the first capacitor switch and the fourth capacitor switch are closed, and the capacitive coupling closed-loop amplifier is connected to the non-inverting output terminal through the level-shifting capacitor.

[0012] According to an ADC driver stage control circuit provided by the present invention, when the ADC is in the second sampling period, the first capacitor switch, the third capacitor switch, the fourth capacitor switch, and the converter switch are disconnected, the second capacitor switch is closed, and the capacitive coupling closed-loop amplifier is connected to the non-inverting output terminal through the level-shifting capacitor.

[0013] According to an ADC driver stage control circuit provided by the present invention, when the ADC is in the conversion period, the level-shifting capacitor is connected to the output terminal of the capacitive coupling closed-loop amplifier.

[0014] According to an ADC driver stage control circuit provided by the present invention, when the ADC is in the first sampling period, the level-shifting capacitor is connected across the output terminal of the capacitive coupling closed-loop amplifier and the sampling capacitor of the ADC.

[0015] In the scenario of the ADC driver stage, since the input of the ADC driver stage is a continuously changing signal, the existing related level-shifting schemes can only play a role in boosting the open-loop gain when the input is DC constant. Therefore, they cannot be applied to the target scenario (programmable voltage gain amplification for continuous input). The ADC driver stage control circuit provided by the present invention adopts a level-shifting capacitor loop to perform relevant level-shifting on the ADC sampling capacitor successively during the ADC sampling period, thereby greatly reducing the voltage swing at the output of the amplifier, improving the linearity of the output voltage of the amplifier. Reducing the output voltage swing realizes programmability, and improving the output voltage linearity realizes voltage gain, which can be applied to high-precision signal chain scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0017] Figure 1 It is a schematic diagram of the ADC driver stage circuit provided by the present invention.

[0018] Figure 2 It is a schematic diagram of the signal instantaneous state of the ADC driving stage circuit provided by the present invention.

[0019] Figure 3 It is a schematic diagram of the signal timing of the ADC driving stage circuit provided by the present invention.

[0020] Figure 4 It is a schematic diagram of the circuit connection of each working state of the ADC driving stage circuit provided by the present invention. Specific Embodiments

[0021] To make the objectives, technical solutions and advantages of the present invention clearer, the technical solutions in the present invention will be clearly and completely described below with reference to the accompanying drawings in the present invention. Apparently, the described embodiments are some but not all of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present invention without creative efforts shall fall within the protection scope of the present invention.

[0022] The following is combined with Figures 1-4 to describe the analog-to-digital converter driving stage control circuit of the present invention.

[0023] Figure 1 It is a schematic diagram of the ADC driving stage circuit provided by the present invention. As Figure 1 shown, the analog-to-digital converter driving stage control circuit includes a non-inverting / inverting input terminal, a capacitive-coupled closed-loop amplifier, a level-shifting capacitor circuit, and a non-inverting / inverting output terminal, where: The non-inverting / inverting input terminal is connected to the input terminal of the capacitive-coupled closed-loop amplifier, and the non-inverting / inverting input terminal is also connected to the input terminal of the level-shifting capacitor circuit; The non-inverting / inverting output terminal is connected to the output terminal of the capacitive-coupled closed-loop amplifier, and the non-inverting / inverting output terminal is also connected to the output terminal of the level-shifting capacitor circuit; The capacitive-coupled closed-loop amplifier is connected in parallel with the level-shifting capacitor circuit; The non-inverting / inverting output terminal is connected to the analog-to-digital converter; During each period of the analog-to-digital converter, the input voltage of the analog-to-digital converter is adjusted by opening and closing the switch in the level-shifting capacitor circuit.

[0024] Specifically, as Figure 1 shown, Figure 1 the schematic diagrams of each component and node in DC servo loop: DC servo loop; : non-inverting input terminal; : inverting input terminal; : non-inverting amplifier output node; : Inverting amplifier output node; : Non-inverting output terminal; : Inverting output terminal; : Common-mode reference voltage; : Variable capacitor with adjustable capacitance. Pseudo R: Pseudo resistor; 、 、 、 : Capacitor switch; : Converter switch; 、 : Level-shifting capacitor; A: Capacitively coupled closed-loop amplifier; : Capacitor.

[0025] By adopting Figure 1 the upper and lower groups of level-shifting capacitors in

[0026] during the ADC sampling period, the relevant level of the ADC sampling capacitor is gradually lifted, thereby greatly reducing the voltage swing at the output of the capacitively coupled closed-loop amplifier and improving the linearity of the output of the capacitively coupled closed-loop amplifier.

[0027] In one embodiment, the level-shifting capacitor circuit provided by the embodiments of the present application includes a DC servo circuit, a variable capacitor, a plurality of capacitor switches, a converter switch, and a level-shifting capacitor, wherein: The DC servo circuit is connected in parallel with the variable capacitor, and the DC servo circuit is also connected in parallel with the capacitively coupled closed-loop amplifier; During each period of the analog-to-digital converter, by changing the switch states of the capacitor switch and the converter switch, the input voltage of the analog-to-digital converter is adjusted.

[0028] In the analog-to-digital converter driving stage control circuit provided by the embodiments of the present application, during each period of the analog-to-digital converter, the capacitively coupled closed-loop amplifier is connected to the non-inverting and inverting output terminals through the converter switch, or the capacitively coupled closed-loop amplifier is connected to the non-inverting and inverting output terminals through the level-shifting capacitor.

[0029] Specifically, the level-lifting capacitor loop in this embodiment includes a first level-lifting capacitor loop and a second level-lifting capacitor loop. Among them, the first level-lifting capacitor loop is Figure 1 the loop between the non-inverting input terminal and the non-inverting output terminal in Figure 1 the loop above the capacitive-coupled closed-loop amplifier in Figure 1 the loop between the inverting input terminal and the inverting output terminal in Figure 1 the loop below the capacitive-coupled closed-loop amplifier in

[0030] In one embodiment, the DC servo loop provided by the embodiment of the present application includes a pseudo-resistor and a target amplifier, where: The pseudo-resistor is connected to the non-inverting and inverting input terminals, and the pseudo-resistor is also connected to the input terminal of the capacitive-coupled closed-loop amplifier; The target amplifier is connected to the output node of the capacitive-coupled closed-loop amplifier.

[0031] For the analog-to-digital converter drive stage control circuit provided by the embodiment of the present application, at each stage of the analog-to-digital converter, the output node is connected to the non-inverting and inverting output terminals through the converter switch, or the output node is connected to the non-inverting and inverting output terminals through the level-lifting capacitor.

[0032] For the analog-to-digital converter drive stage control circuit provided by the embodiment of the present application, when the analog-to-digital converter is in the conversion stage, the first capacitor switch and the second capacitor switch among the multiple capacitor switches are disconnected, and the third capacitor switch, the fourth capacitor switch and the converter switch among the multiple capacitor switches are closed. The capacitive-coupled closed-loop amplifier is connected to the non-inverting and inverting output terminals through the converter switch; The multiple capacitor switches and the converter switch are arranged between the capacitive-coupled closed-loop amplifier and the non-inverting and inverting output terminals; the first capacitor switch and the second capacitor switch are in parallel, and the third capacitor switch and the fourth capacitor switch are in series.

[0033] For the analog-to-digital converter drive stage control circuit provided by the embodiment of the present application, when the analog-to-digital converter is in the conversion stage, the level-lifting capacitor is connected to the output terminal of the capacitive-coupled closed-loop amplifier.

[0034] Specifically, when the ADC is in the conversion stage, that is, Figure 4 in the AMP Tracking-Conversion period in Figure 1 the switch connection state in the overall circuit diagram of and the switch is disconnected, 、 and The switch is closed, where is the first capacitance switch in this embodiment; is the second capacitance switch in this embodiment; is the third capacitance switch in this embodiment; is the fourth capacitance switch in this embodiment; is the converter switch in this embodiment. The overall simplified circuit connection state is as shown in Figure 4 the circuit corresponding to the AMP Tracking-Conversion period in Figure 1 The upper and lower groups of level-lifting capacitors in and are connected to the output end of the amplifier for rough amplification and following. Since the output swing of the capacitive-coupled closed-loop amplifier is rail-to-rail, when the input is close to the power supply or ground, the rough amplified output voltages on the level-lifting capacitors and have large distortion and saturation.

[0035] Figure 4 The corresponding part of each cycle in the schematic diagram of the signal instantaneous state during the AMP Tracking-Conversion period in Figure 2 The corresponding part of each cycle in the schematic diagram of the signal instantaneous state during the AMP Tracking-Conversion period in corresponding part. Figure 2 The curve in and represents the differential signal amount between Figure 2 The curve in and represents the differential signal amount between Figure 2 The curve in and represents the differential signal amount between Figure 2 The in is the power supply voltage; Signal Swing: signal swing; AMP Swingin CLS2: swing of the AMP signal in CLS2;

[0036] In one embodiment, for the analog-to-digital converter drive stage control circuit provided by the embodiments of the present application, when the analog-to-digital converter is in the first sampling period, the second capacitor switch, the third capacitor switch, and the converter switch are disconnected, the first capacitor switch and the fourth capacitor switch are closed, and the capacitive coupling closed-loop amplifier is connected to the non-inverting output terminal through the level-lifting capacitor.

[0037] For the analog-to-digital converter drive stage control circuit provided by the embodiments of the present application, when the analog-to-digital converter is in the first sampling period, the level-lifting capacitor is connected across the output terminal of the capacitive coupling closed-loop amplifier and the sampling capacitor of the analog-to-digital converter.

[0038] Specifically, when the ADC enters the sampling stage, that is, Figure 4 during the CLS1-Sampling (CLS1 sampling) period in Figure 1 the switch connection states in the overall circuit diagram are as follows: 、 and the switches are disconnected, and the switches are closed. Thus, the overall simplified circuit connection is as shown in the circuit corresponding to the CLS1-Sampling period in Figure 4 The capacitance CLS1 changes its connection method and is connected across the output of the capacitive coupling closed-loop amplifier and the ADC sampling capacitor. Its function of lifting the level can reduce the output voltage swing of the capacitive coupling closed-loop amplifier, and at the same time make the capacitance CLS2 and the ADC sampling capacitor more accurately follow the input signal. However, since the input signal changes continuously, after sampling and following for a period of time, the voltage swing at the output node of the capacitive coupling closed-loop amplifier will become larger, which will change the overall linearity to a certain extent.

[0039] In one embodiment, for the analog-to-digital converter drive stage control circuit provided by the embodiments of the present application, when the analog-to-digital converter is in the second sampling period, the first capacitor switch, the third capacitor switch, the fourth capacitor switch, and the converter switch are disconnected, the second capacitor switch is closed, and the capacitive coupling closed-loop amplifier is connected to the non-inverting output terminal through the level-lifting capacitor.

[0040] Specifically, after a period of time, the capacitive coupling closed-loop amplifier enters the second stage of related level-lifting, that is, Figure 4 during the CLS2-Sampling (CLS2 sampling) period in Figure 1 the switch connection states in the overall circuit diagram are as follows: 、 、 and the switches are disconnected, The switch is closed, and the overall simplified circuit connection is as Figure 4 shown in the circuit corresponding to the CLS2 - Sampling period. CLS1 is disconnected from the overall circuit, and CLS2 is cross - connected to achieve the second level boost. After this boost, the voltage swing at the output node of the capacitive - coupled closed - loop amplifier is further reduced. In addition, since there have been two level boosts, during this period, the capacitive - coupled closed - loop amplifier requires a very small stable voltage error. Therefore, the time setting for this period can be very short. As a result, the output swing variation of the capacitive - coupled closed - loop amplifier caused by the continuously changing input is very small, thus ensuring that the voltage at the end of the ADC sampling can reach a very high linearity.

[0041] The signal timings corresponding to the above three stages are as Figure 3 shown, where ADC conversion is the ADC conversion.

[0042] The rail - to - rail high - linearity analog - to - digital converter driver - stage control circuit based on the continuous - time level - boost scheme proposed in this application can be used for the driver stage of the ADC. It only needs to adopt the same power supply rail as the ADC. Therefore, it also reduces the power consumption overhead of the ADC driver stage, simplifies the system design complexity, and improves the system energy efficiency. In terms of performance, the continuous - time level - boost scheme proposed in this application can achieve extremely high linearity. For example, it has a spurious - free dynamic range (SFDR) greater than 100 dB and can be widely applied to various application scenarios of high - precision signal - chain systems.

[0043] This application has been tape - out and verified under the 55 - nm chip process. At a power supply voltage of 1.2 V, the chip prototype integrating the analog - to - digital converter driver - stage control circuit and the ADC provided in this application achieved a signal - to - noise - and - distortion ratio (SNDR) of 82.9 dB, an SFDR of 105.4 dB, and a power consumption of 1.12 mW (milli - watt) within a signal bandwidth of 2.5 MHz at a sampling rate of 40 Msps (millions of samples per second). This application also tested and verified the programmable gain function of the amplifier. At gains of 1 times and 2 times, the continuous - time related level - boost technology can achieve very high linearity in the case of the amplifier's rail - to - rail output.

[0044] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An analog-to-digital converter drive stage control circuit, characterized in that: The analog-to-digital converter driving stage control circuit includes in-phase and inverting input terminals, a capacitive coupling closed-loop amplifier, a level-lifting capacitor loop and in-phase and inverting output terminals, wherein: The in-phase and inverting input terminals are connected to the input terminals of the capacitive coupling closed-loop amplifier, and the in-phase and inverting input terminals are also connected to the input terminals of the level-raising capacitor loop; The in-phase and inverting output terminals are connected to the output terminal of the capacitive coupling closed-loop amplifier, and the in-phase and inverting output terminals are also connected to the output terminal of the level-raising capacitor loop; The capacitive coupling closed-loop amplifier is connected in parallel with the level-raising capacitive loop; The in-phase and inverting output terminals are connected to an analog-to-digital converter; In each period of the analog-to-digital converter, the input voltage of the analog-to-digital converter is adjusted by opening and closing the switch in the level-raising capacitor loop.

2. The analog-to-digital converter driving stage control circuit according to claim 1, characterized in that: The level-raising capacitor loop includes a DC servo loop, a variable-capacitance capacitor, a plurality of capacitor switches, a converter switch and a level-raising capacitor, wherein: The DC servo loop is connected in parallel with the variable capacitance capacitor, and the DC servo loop is also connected in parallel with the capacitive coupling closed-loop amplifier; In each period of the analog-to-digital converter, the input voltage of the analog-to-digital converter is adjusted by changing the switching states of the plurality of capacitor switches and the converter switch.

3. The analog-to-digital converter driving stage control circuit according to claim 2, characterized in that: In each period of the analog-to-digital converter, the capacitive coupling closed-loop amplifier is connected to the in-phase and inverting output terminals through the converter switch, or the capacitive coupling closed-loop amplifier is connected to the in-phase and inverting output terminals through the level-raising capacitor.

4. The analog-to-digital converter driving stage control circuit according to claim 2, characterized in that: The DC servo loop includes a pseudo resistor and a target amplifier, wherein: The pseudo resistor is connected to the in-phase and inverting input terminals, and the pseudo resistor is also connected to the input terminal of the capacitive coupling closed-loop amplifier; The target amplifier is connected to an output node of the capacitively coupled closed-loop amplifier.

5. The analog-to-digital converter driving stage control circuit according to claim 4, characterized in that: In each period of the analog-to-digital converter, the output node is connected to the in-phase and inverting output terminals through the converter switch, or the output node is connected to the in-phase and inverting output terminals through the level-raising capacitor.

6. The analog-to-digital converter driving stage control circuit according to claim 2, characterized in that: When the analog-to-digital converter is in a conversion period, the first capacitor switch and the second capacitor switch among the plurality of capacitor switches are disconnected, and the third capacitor switch, the fourth capacitor switch and the converter switch among the plurality of capacitor switches are closed, and the capacitor-coupled closed-loop amplifier is connected to the in-phase and inverting output terminals through the converter switch; A plurality of capacitor switches and the converter switch are arranged between the capacitor coupling closed-loop amplifier and the in-phase and inverting output terminals; the first capacitor switch and the second capacitor switch are connected in parallel, and the third capacitor switch and the fourth capacitor switch are connected in series.

7. The analog-to-digital converter driving stage control circuit according to claim 6, characterized in that: When the analog-to-digital converter is in the first sampling period, the second capacitor switch, the third capacitor switch and the converter switch are disconnected, the first capacitor switch and the fourth capacitor switch are closed, and the capacitively coupled closed-loop amplifier is connected to the in-phase and inverting output terminals through the level-raising capacitor.

8. The analog-to-digital converter driving stage control circuit according to claim 6, characterized in that: When the analog-to-digital converter is in the second sampling period, the first capacitor switch, the third capacitor switch, the fourth capacitor switch and the converter switch are disconnected, the second capacitor switch is closed, and the capacitively coupled closed-loop amplifier is connected to the in-phase and inverting output terminals through the level-raising capacitor.

9. The analog-to-digital converter driving stage control circuit according to claim 1, characterized in that: When the analog-to-digital converter is in a conversion period, the level-raising capacitor is connected to the output end of the capacitive-coupled closed-loop amplifier.

10. The analog-to-digital converter driving stage control circuit according to claim 1, characterized in that: When the analog-to-digital converter is in a first sampling period, the level-raising capacitor is connected across the output end of the capacitive-coupled closed-loop amplifier and the sampling capacitor of the analog-to-digital converter.

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