High-linearity digital-to-analog converter

Abstract

The invention discloses a digital-to-analog converter with high linearity. The digital-to-analog converter comprises a dynamic element matching circuit, a cross point adjusting circuit, a current source array, a switching circuit, a comparator module, a load resistor module and a feedback resistor module, the dynamic element matching circuit converts the digital input signal of a binary code into a control signal of a pseudo-random thermometer code, and the cross point adjusting circuit adjusts the control signal and inputs the control signal into the switching circuit to control the switching circuit. The digital-to-analog converter converts a traditional current source array with a current value in a binary multiple relationship into a current source with a current value being a single value, and selects by using a pseudo-random thermometer code control signal adjusted by a cross point, so that the current mismatch is relatively small, the mismatch between the current sources is converted into pseudo-random noise, and the noise is reduced. And the linearity of the digital-to-analog converter is effectively improved.

Description

Technical Field

[0001] The invention belongs to the technical field of integrated circuits, and in particular relates to a high-linearity digital-to-analog converter. Background Art

[0002] A digital to analog converter (DAC) is a signal converter that converts digital signals into analog signals and is widely used in the field of signal processing.

[0003] There are many types of digital-to-analog converters, and current-steering digital-to-analog converters are one of the more common structures. They have the advantages of high matching accuracy and fast response speed, and are widely used in high-speed circuits with high matching requirements. In addition, current-steering digital-to-analog converters have a high energy utilization rate, and can output almost all of the energy when the output signal is used differentially.

[0004] However, conventional current-steering DACs use current source arrays whose current values ​​are binary multiples. Since the current source is limited by the matching accuracy of the resistor value, when the resistor values ​​are not exactly the same due to process, photolithography, etc., mismatches are inevitable, which directly affects the linearity of the DAC. The linearity that the DAC can achieve depends to a certain extent on the mismatch error of the current source. Therefore, how to reduce the current mismatch of the current source array and thus improve the linearity of the DAC is a technical problem that needs to be solved urgently. Summary of the invention

[0005] In view of the problems existing in the prior art, the present invention proposes a high-linearity digital-to-analog converter, which converts a binary digital input signal into a pseudo-random thermometer code control signal output by introducing a dynamic element matching circuit, converts a traditional current source array whose current values ​​are binary multiples into a current source with a single current value, and controls it with a pseudo-random thermometer code control signal. Since the above-mentioned digital-to-analog converter converts the traditional current source array whose current values ​​are binary multiples into a current source with a single current value, and selects it by using a pseudo-random thermometer code control signal with a cross-point adjusted, the current mismatch is relatively small, and the mismatch between current sources is converted into pseudo-random noise, thereby effectively improving the linearity of the digital-to-analog converter.

[0006] In order to achieve the above technical objectives, the present invention adopts the following technical solutions: The present invention discloses a high-linearity digital-to-analog converter, which includes a dynamic element matching circuit, a crosspoint adjustment circuit, a current source array, a switch circuit, a comparator module, a load resistance module and a feedback resistance module; One end of the dynamic element matching circuit is connected to a digital input signal, the other end of the dynamic element matching circuit is connected to one end of the cross point adjustment circuit, the other end of the cross point adjustment circuit is connected to one end of the switch circuit, the switch circuit is also connected to the current source array, the load resistance module and the reverse input end of the comparator module, the output end of the comparator module is connected to one end of the feedback resistance module, and the other end of the feedback resistance module is respectively connected to the reverse input end of the comparator module and one end of the load resistance module; The dynamic element matching circuit converts the digital input signal of binary code into a control signal of pseudo-random thermometer code, and the cross point adjustment circuit adjusts the control signal and inputs it into the switch circuit to control the switch circuit.

[0007] Optional: The binary code digital input signal is D <i-1:0>, including D <0> ~ D <i-1>The i signal is a natural number greater than or equal to 2.

[0008] Optional: The dynamic element matching circuit converts the i-bit binary code digital input signal D <i-1:0>Convert to 2 i -1-bit pseudo-random thermometer code control signal K<2 i -1:1>, assuming that K<2 after the mth conversion i -1:1> The first multiple consecutive bits are 1, and the last bit of the consecutive bits is K <j>, then at the m+1th conversion, if D <i-1:0>The corresponding decimal number is p, j+p is less than or equal to 2 i When -1, K<2 i -1:1>K<j+1:j+p> The first bit is 1, the rest are 0, j+p is greater than 2 i -1, then K<2 i -1:1>K <j+1: 2 i -1> and K<1: j+p-2 i +1> is 1, and the rest are 0, where m is a natural number greater than or equal to 1.

[0009] Optionally: the cross point adjustment circuit sets the pseudo-random thermometer code control signal K<2 i -1:1> The cross-point adjustment circuit of the inverting circuit formed by the cascaded N-tube and P-tube is converted into a common-phase control signal Q<2 i -1:1> and inverting control signal QB<2 i -1:1>, and the output signal Q<2 i -1:1> and QB<2 i The crossover point of -1:1> is below the common-mode voltage.

[0010] Optional: The current source array includes 2 i -1 current source I with the same current value, the switch circuit includes 2 i -1 pair of switches, one end of each current source I is connected to each pair of switches, and each pair of switches is respectively controlled by a control signal Q <n>and QB <n>control, the control signal QB <n>The other end of the switch controlled by the control signal Q is connected to the load resistor R00. <n>The other end of the controlled switch is connected to the load resistor R0 and the inverting input end of the comparator module, and n is 1 to 2. i A natural number equal to -1.

[0011] Optionally: the comparator module includes a comparator based on an operational amplifier, the comparator includes a non-phase input terminal, an inverting input terminal and an output terminal, wherein the positive input terminal is connected to a reference voltage Vref, and the inverting input terminal is respectively connected to a switching circuit, one end of a feedback resistor module and one end of a load resistor module.

[0012] Optional: The load resistor module includes a load resistor R0 and a load resistor R00 with equal resistance values, one end of the load resistor R0 is respectively connected to the switching circuit and the reverse input end of the comparator, one end of the load resistor R00 is connected to the switching circuit, and the other ends of the load resistor R0 and the load resistor R00 are grounded.

[0013] Optionally, the feedback resistor module includes a feedback resistor R1, one end of the feedback resistor R1 is connected to the input end of the comparator, and the other end of the feedback resistor R1 is connected to the reverse input end of the comparator.

[0014] Optionally: the output voltage Vout of the digital-to-analog converter is:

[0015] in, is the voltage value of the reference voltage, is the resistance value of the feedback resistor R1, is the resistance value of the load resistor R0, is the current value of the current source I, is the digital input signal D <n>The value of , n is a natural number from 0 to i-1.

[0016] The beneficial effects of the present invention are as follows: The present invention proposes a high-linearity digital-to-analog converter, which includes a dynamic element matching circuit, a crosspoint adjustment circuit, a current source array, a switch circuit, a comparator module, a load resistance module and a feedback resistance module. One end of the dynamic element matching circuit is connected to a digital input signal, and the other end of the dynamic element matching circuit is connected to one end of the crosspoint adjustment circuit. The other end of the crosspoint adjustment circuit is connected to one end of the switch circuit. One end of the switch circuit is connected to the current source array, one end is connected to one of the load resistors, and the other end is connected to the reverse input end of the comparator module. The output end of the comparator module is connected to one end of the feedback resistance module, and the other end of the feedback resistance module is respectively connected to the reverse input end of the comparator module and one end of the load resistance module. The dynamic element matching circuit converts a binary code digital input signal into a pseudo-random thermometer code control signal, and the signal is used to control the switch circuit after passing through the crosspoint adjustment circuit. The above-mentioned digital-to-analog converter converts a traditional current source array with current values ​​in binary multiples into a current source with a single current value, and selects it by using a pseudo-random thermometer code control signal with cross-point adjustment, so that the current mismatch is relatively small, and the mismatch between current sources is converted into pseudo-random noise, thereby effectively improving the linearity of the digital-to-analog converter. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only 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 work.

[0018] Figure 1 A circuit structure diagram of a high linearity digital-to-analog converter proposed in an embodiment of the present invention; Figure 2 A circuit schematic diagram of a high linearity digital-to-analog converter proposed in an embodiment of the present invention; Figure 3 An example of cross point adjustment of a control signal by a cross point adjustment circuit according to an embodiment of the present invention; Reference numerals: 1. Dynamic element matching circuit; 2. Cross-point adjustment circuit; 3. Current source array; 4. Comparator module; 5. Switching circuit; 6. Load resistance module; 7. Feedback resistance module. DETAILED DESCRIPTION

[0019] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0020] In addition, the term "and / or" in this article is only a description of the association relationship of the associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0021] like Figure 1 As shown, an embodiment of the present invention proposes a high linearity digital-to-analog converter, which includes a dynamic element matching circuit 1, a crosspoint adjustment circuit 2, a current source array 3, a comparator module 4, a switch circuit 5, a load resistance module 6 and a feedback resistance module 7.

[0022] One end of the dynamic element matching circuit 1 is connected to a digital input signal, the other end of the dynamic element matching circuit 1 is connected to one end of the cross point adjustment circuit 2, the other end of the cross point adjustment circuit 2 is connected to one end of the switch circuit 5, the switch circuit 5 is also connected to the current source array 3, the load resistance module 6 and the reverse input end of the comparator module 4, the output end of the comparator module 4 is connected to one end of the feedback resistance module 7, and the other end of the feedback resistance module 7 is respectively connected to the reverse input end of the comparator module 4 and one end of the load resistance module 6.

[0023] The dynamic element matching circuit 1 converts the digital input signal of binary code into a control signal of pseudo-random thermometer code, and the cross point adjustment circuit 2 adjusts the control signal and inputs it into the switch circuit 5 to control the switch circuit 5 .

[0024] The dynamic element matching circuit 1 of the present application converts a binary digital input signal into a pseudo-random thermometer code control signal, and uses it to control the switch circuit 5 after passing through the cross point adjustment circuit 2. The above-mentioned digital-to-analog converter converts the traditional current source array 3 whose current value is in a binary multiple relationship into a current source with a single current value, and selects it by using the pseudo-random thermometer code control signal with cross point adjustment, so that the current mismatch is relatively small, and the mismatch between current sources is converted into pseudo-random noise, thereby effectively improving the linearity of the digital-to-analog converter.

[0025] Exemplarily, the dynamic element matching circuit converts the digital input signal D of the i-bit binary code into <i-1:0>Convert to 2 i -1-bit pseudo-random thermometer code control signal K<2 i -1:1>, assuming that K<2 after the mth conversion i -1:1> The first multiple consecutive bits are 1, and the last bit of the consecutive bits is K <j>, then at the m+1th conversion, if D <i-1:0>The corresponding decimal number is p, j+p is less than or equal to 2 i -1, K<2 i -1:1>K<j+1:j+p> The first bit is 1, the rest are 0, j+p is greater than 2 i -1, then K<2 i -1:1>K <j+1: 2 i -1> and K<1: j+p-2 i +1> is 1, and the rest of the bits are 0, where m is a natural number greater than or equal to 1. The upper limit of m can be set according to actual needs.

[0026] In an optional embodiment, the cross point adjustment circuit 2 controls the pseudo-random thermometer code signal K<2 i -1:1> The cross-point adjustment circuit of the inverting circuit is converted into a common-phase control signal Q<2 by cascading a large width-to-length ratio N tube and a small width-to-length ratio P tube to form an inverting circuit. i -1:1> and inverting control signal QB<2 i -1:1>, and the output signal Q<2 i -1:1> and QB<2 i -1:1> The falling edge is faster and the rising edge is slower, so that the intersection point is lower than the common mode voltage. Among them, the large aspect ratio N tube and the small aspect ratio P tube can be selected according to the actual situation, so that the selected N tube and P tube can achieve the corresponding function, and this application does not limit this.

[0027] In an optional embodiment, the current source array 3 and the switch circuit 5 include 2 i -1 current source I and 2 with the same current value i -1 pair of switches, one end of each current source I is connected to each pair of switches, and each pair of switches is respectively controlled by a control signal Q <n>and QB <n>control, the control signal QB <n>The other end of the switch controlled by the control signal Q is connected to the load resistor R00. <n>The other end of the controlled switch is connected to the load resistor R0 and the inverting input end of the comparator module 4, and n is 1 to 2. i A natural number equal to -1.

[0028] In an optional embodiment, the comparator module 4 includes a comparator based on an operational amplifier, including a non-phase input terminal, an inverting input terminal and an output terminal, wherein the non-phase input terminal is connected to a reference voltage Vref, the inverting input terminal is respectively connected to the switching circuit 5, one end of the feedback resistor module 7, and one end of the load resistor module 6, and the output terminal outputs a corresponding voltage.

[0029] In an optional embodiment, the load resistor module 6 includes load resistors R0 and R00, one end of the load resistor R0 is connected to the reverse input terminal of the comparator module 4, the other end of the load resistor R0 is grounded, and the other end of the load resistor R00 is grounded, and the two resistors have equal resistance values. Specifically, the resistance value of the load resistor R1 is R, and the specific value of R needs to be specifically set according to actual conditions, and is only used as an identifier here.

[0030] The feedback resistor module 7 includes a feedback resistor R1 , one end of the feedback resistor R1 is connected to the inverting input end of the comparator module 4 , and the other end of the feedback resistor R1 is connected to the output end of the comparator module 4 .

[0031] The above-mentioned high-linearity digital-to-analog converter introduces a dynamic element matching circuit 1 to convert a binary digital input signal into a pseudo-random thermometer code control signal output, converts a traditional current source array 3 whose current values ​​are in a binary multiple relationship into a current source with a single current value, and controls it with a pseudo-random thermometer code control signal. Since the above-mentioned digital-to-analog converter converts the traditional current source array 3 whose current values ​​are in a binary multiple relationship into a current source with a single current value, and selects it by using a pseudo-random thermometer code control signal with a crosspoint adjusted, the current mismatch is relatively small, and the mismatch between current sources is converted into pseudo-random noise, thereby effectively improving the linearity of the digital-to-analog converter.

[0032] In an optional embodiment, if Figure 2 As shown, the output voltage Vout of the digital-to-analog converter is:

[0033] in, is the voltage value of the reference voltage, is the resistance value of the feedback resistor R1, is the resistance value of the load resistor R0, is the current value of the current source I, is the digital input signal D <n>The value of , n is a natural number from 0 to i-1.

[0034] It should be noted that in actual applications, technical personnel in this application can set the values ​​of components such as Vref, I, R0 and R1 according to actual needs to make the analog output voltage of the digital-to-analog converter within the required range, and this application does not limit this.

[0035] Table 1 shows a specific example of the high linearity digital-to-analog converter of the present invention. This specific example discloses a conversion example of the dynamic element matching circuit 1 when a 4-bit data input signal is used.

[0036] Table 1

[0037] As shown in Table 1, the digital input signal is D<3:0>, which includes D <0> , D <1> , D <2> and D <3> If there are four signals, D<3:0> can be 1000, 1001, 1010…0111. 4 =16 signals. Then D<3:0> can be converted to get K <1> ~K <15> For example, suppose the K corresponding to the data input signal 1000 after the mth conversion is <1> ~K <8> bit is 1, K <9> ~K <15> The last bit of the consecutive bits is K. <8> , then at the m+1th conversion, the decimal number corresponding to the data input signal 1001 input after 1000 is 9, j+p=8+9=17, 17 is greater than 15, that is, j+p>2 i -1, then K<2 i -1:1>K <j+1: 2 i -1> and K<1: j+p-2 i +1> is 1, that is, K<9: 15> and K<1: 2> are 1, and the rest are 0. Therefore, in the control signal of the 15-bit pseudo-random thermometer code corresponding to 1001, K <1> ~K <2> and K <9> ~ K <15> is 1, and the rest are 0, where m is a natural number greater than or equal to 1. The upper limit of m can be set according to actual needs.

[0038] like Figure 3 FIG. 1 is an example of the cross point adjustment circuit 2 of the present invention for adjusting the cross point of the control signal, where n is 1 to 2. i -1 is a natural number. Figure 3 It can be seen from FIG. 2 that the cross point of the output signal of the cross point adjustment circuit 2 is lower than the common mode voltage.

[0039] In summary, the present invention proposes a high-linearity digital-to-analog converter, which includes a dynamic element matching circuit 1, a crosspoint adjustment circuit 2, a current source array 3, a switch circuit 5, a comparator module 4, a load resistance module 6 and a feedback resistance module 7. One end of the dynamic element matching circuit 1 is connected to a digital input signal, and the other end of the dynamic element matching circuit 1 is connected to one end of the crosspoint adjustment circuit 2, and the other end of the crosspoint adjustment circuit 2 is connected to one end of the switch circuit 5. One end of the switch circuit 5 is connected to the current source array 3, one end is connected to one of the load resistors, and the other end is connected to the reverse input end of the comparator module 4. The output end of the comparator module 4 is connected to one end of the feedback resistance module 7, and the other end of the feedback resistance module 7 is respectively connected to the reverse input end of the comparator module 4 and one end of the load resistance module 6. The dynamic element matching circuit 1 converts the digital input signal of the binary code into a pseudo-random thermometer code control signal, and is used to control the switch circuit 5 after passing through the crosspoint adjustment circuit 2. The above-mentioned digital-to-analog converter converts the traditional current source array 3 whose current value is a binary multiple relationship into a current source with a single current value, and selects it by using a pseudo-random thermometer code control signal with cross-point adjustment, so that the current mismatch is relatively small, and the mismatch between current sources is converted into pseudo-random noise, thereby effectively improving the linearity of the digital-to-analog converter.

[0040] Through the description of the above implementation methods, technicians in the relevant field can clearly understand that for the convenience and simplicity of description, only the division of the above functional units is used as an example. In actual applications, the above functions can be assigned to different functional units as needed, that is, the internal structure of the device is divided into different functional units to complete all or part of the functions described above. The specific working process of the system, device and unit described above can refer to the corresponding process in the aforementioned method embodiment, and will not be repeated here.

[0041] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.< / n> < / n> < / n> < / n> < / n> < / j> < / n> < / n> < / n> < / n> < / n> < / j>

Claims

1. A high linearity digital-to-analog converter, characterized in that: The digital-to-analog converter includes a dynamic element matching circuit, a crosspoint adjustment circuit, a current source array, a switch circuit, a comparator module, a load resistance module and a feedback resistance module; One end of the dynamic element matching circuit is connected to a digital input signal, the other end of the dynamic element matching circuit is connected to one end of the cross point adjustment circuit, the other end of the cross point adjustment circuit is connected to one end of the switch circuit, the switch circuit is also connected to the current source array, the load resistance module and the reverse input end of the comparator module, the output end of the comparator module is connected to one end of the feedback resistance module, and the other end of the feedback resistance module is respectively connected to the reverse input end of the comparator module and one end of the load resistance module; The dynamic element matching circuit converts the digital input signal of binary code into a control signal of pseudo-random thermometer code, and the cross point adjustment circuit adjusts the control signal and inputs it into the switch circuit to control the switch circuit.

2. The high linearity digital-to-analog converter according to claim 1, characterized in that: The binary code digital input signal is D <i-1:0>, including D <0> ~ D <i-1> The i signal is a natural number greater than or equal to 2.< / i-1> 3. The high linearity digital-to-analog converter according to claim 2, characterized in that: The dynamic element matching circuit converts the digital input signal D of the i-bit binary code into <i-1:0>Convert to 2 i -1-bit pseudo-random thermometer code control signal K<2 i -1:1>, assuming that K<2 after the mth conversion i -1:1> The first multiple consecutive bits are 1, and the last bit of the consecutive bits is K <j>, then at the m+1th conversion, if D <i-1:0>The corresponding decimal number is p, j+p is less than or equal to 2 i -1, K<2 i -1:1>K<j+1:j+p> The first bit is 1, the rest are 0, j+p is greater than 2 i -1, then K<2 i -1:1>K <j+1: 2 i -1> and K< 1: j+p-2 i +1> is 1, and the rest are 0, where m is a natural number greater than or equal to 1. < / j> 4. The high linearity digital-to-analog converter according to claim 3, characterized in that: The cross point adjustment circuit controls the pseudo-random thermometer code signal K<2 i -1:1> The cross-point adjustment circuit of the inverting circuit formed by the cascaded N-tube and P-tube is converted into a common-phase control signal Q<2 i -1:1> and inverting control signal QB<2 i -1:1>, and the output signal Q<2 i -1:1> and QB<2 i The crossover point of -1:1> is below the common-mode voltage.

5. The high linearity digital-to-analog converter according to claim 4, characterized in that: The current source array includes 2 i -1 current source I with the same current value, the switch circuit includes 2 i -1 pair of switches, one end of each current source I is connected to each pair of switches, and each pair of switches is respectively controlled by a control signal Q <n>and QB <n>control, the control signal QB <n>The other end of the switch controlled by the control signal Q is connected to the load resistor R00. <n>The other end of the controlled switch is connected to the load resistor R0 and the inverting input end of the comparator module, and n is 1 to 2. i A natural number equal to -1.< / n> < / n> < / n> < / n> 6. The high linearity digital-to-analog converter according to any one of claims 1 to 5, characterized in that: The comparator module includes a comparator based on an operational amplifier, and the comparator includes a non-inverting input terminal, an inverting input terminal and an output terminal, wherein the non-inverting input terminal is connected to a reference voltage Vref, and the inverting input terminal is respectively connected to a switch circuit, one end of a feedback resistor module and one end of a load resistor module.

7. The high linearity digital-to-analog converter according to claim 6, characterized in that: The load resistor module includes a load resistor R0 and a load resistor R00 with equal resistance values, one end of the load resistor R0 is respectively connected to the switching circuit and the reverse input end of the comparator, one end of the load resistor R00 is connected to the switching circuit, and the other ends of the load resistor R0 and the load resistor R00 are grounded.

8. The high linearity digital-to-analog converter according to claim 7, characterized in that: The feedback resistor module includes a feedback resistor R1 , one end of the feedback resistor R1 is connected to the input end of the comparator, and the other end of the feedback resistor R1 is connected to the inverting input end of the comparator.

9. The high linearity digital-to-analog converter according to claim 8, characterized in that: The output voltage Vout of the digital-to-analog converter is: in, is the voltage value of the reference voltage, is the resistance value of the feedback resistor R1, is the resistance value of the load resistor R0, is the current value of the current source I, is the digital input signal D <n> The value of , n is a natural number from 0 to i-1.< / n>

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