WO2021258949A1

WO2021258949A1 - Current steering digital-to-analog converter based on hybrid coding

Info

Publication number: WO2021258949A1
Application number: PCT/CN2021/095281
Authority: WO
Inventors: 董蕾; 王立峰; 易真翔
Original assignee: 东南大学
Priority date: 2020-06-22
Filing date: 2021-05-21
Publication date: 2021-12-30
Also published as: CN111900990A

Abstract

A current steering digital-to-analog converter based on hybrid coding, comprising a decoding circuit, a current source module, a comparator module, a load resistor module, and a feedback resistor module. The decoding circuit converts a digital input signal of a binary code into a hybrid coding digital control signal formed by by a high-order part thermometer code and a low-order part binary code; the current source module is controlled by the hybrid coding digital control signal; a conventional current source array having current values in a binary multiple relation is converted into current sources having the same current value; and both a resistance value and the current value are single values, so that the current mismatch is relatively small, thereby effectively improving the conversion precision of a digital-to-analog converter.

Description

A current rudder type digital-to-analog converter based on mixed coding

Technical field

The invention relates to integrated circuit technology, in particular to a current steering type digital-to-analog converter based on hybrid coding, which belongs to the technical field of basic electronic circuits.

Background technique

Digital to Analog Converter (DAC) is a signal converter that can convert digital signals into analog signals, and is widely used in various fields that require signal processing. There are many types of digital-to-analog converters. Among them, the current steering digital-to-analog converter (Current Steering Digital to Analog Converter) is a commonly used digital-to-analog converter structure, which has the advantages of high matching accuracy and fast response speed. And it has a wide range of applications in circuits with higher matching requirements, and the current steering type digital-to-analog converter has a higher energy utilization rate. When the output signal is used differentially, almost all the energy can be output.

However, the conventional current steering digital-to-analog converter uses a current source array whose current value is a binary multiple. Because the current source is limited by the matching accuracy of the resistance value, the resistance value is not exactly the same due to reasons such as process and photolithography. At this time, there is inevitably a mismatch, which directly affects the accuracy of the digital-to-analog conversion. The accuracy that the digital-to-analog converter 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 thereby improve the conversion accuracy of the digital-to-analog converter is an urgent technical problem to be solved.

Summary of the invention

The purpose of the present invention is to address the shortcomings of the above-mentioned background technology and provide a current-steering digital-to-analog converter based on hybrid coding, which converts the digital input signal of the binary code into the high-order part of the thermometer code and the low-order part by introducing a decoding circuit The binary code mixed coded digital control signal converts the traditional current value into a binary multiple relationship current source array into a current source with the same current value, and uses the mixed coded digital signal of the high part of the thermometer code and the low part of the binary code for control. The resistance value and current value in the source array are both a single value, making the current mismatch of the current source array relatively small, thereby effectively improving the conversion accuracy of the current steering type digital-to-analog converter, and solving how to reduce the current steering type digital-to-analog converter The technical problem of the current mismatch of the current source array.

The present invention adopts the following technical solutions to achieve the above-mentioned purpose of the invention:

A current steering digital-to-analog converter based on hybrid coding, including:

Decoding circuit, whose input terminal is connected with a binary digital signal of n+m bits, and converts the digital input signal of the lower part of the n-bit binary code into the digital control signal of the n-bit binary code of K0, K1···Kn-1. The code circuit converts the digital input signal of the high-order m-bit binary code into the digital control signal of the 2^m-1 digit thermometer code of S1, S2···S2^m-1, and the n and m bits are natural numbers greater than or equal to 1, ；

The current source module includes a current source array whose output current value is I and controlled by the low-order part of the binary code, and the current source array whose output current value is 2I and is controlled by the high-order part of the thermometer code, and the output current value is I. An R-2R network is connected between the output terminal of the source array and the ground, and the output terminals of the two power arrays are connected in parallel as the output terminal of the current source module;

Comparator module, whose non-inverting input terminal is connected to the reference voltage, and its inverting input terminal is connected to one end of the load resistance module and the output terminal of the current source module to output an analog voltage signal;

Load resistance module, the other end of which is grounded together with the current source module; and,

The feedback resistance module is connected between the inverting input terminal and the output terminal of the comparator module.

Further, the current source array whose output current value is I and controlled by the low-order part of the binary code includes: n current source branches with current value I, each current source branch is connected in series with a switch tube, and each switch tube receives Controlled by the one-bit code of the low-order part of the binary code, the R-2R network includes n-1 first resistors and n-2 second resistors. The m-th first resistor is connected to the output terminal of the first current source branch and Between ground, the p-th second resistor is connected between the p-th current source output terminal and the p+1-th current source output terminal, 0≤m≤n-1, 0≤p≤n-2, when m When = 0, the resistance of the first resistor is R, and when 0<m<n, the resistance of the first resistor is 2R.

Further, the current source array with an output current value of 2I and controlled by a high-level thermometer code includes 2^m-1 current source branches with a current value of 2I, and each current source branch is connected in series with a switch tube, each The switch tube is controlled by the one-bit code of the upper part of the thermometer code.

Further, the comparator module includes a comparator based on an operational amplifier, and the non-inverting input terminal of the comparator is connected to the reference voltage Vref.

Further, the feedback resistance module includes a feedback resistance Rf, one end of the feedback resistance Rf is connected to the inverting input end of the comparator module, and the other end of the feedback resistance Rf is connected to the output end of the comparator module.

Further, the load resistance module includes a load resistance R1, one end of the load resistance R1 is connected to the inverting input terminal of the comparator module, and the other end of the load resistance R1 is grounded.

Further, the output voltage Vout of the current steering digital-to-analog converter based on hybrid coding is:

Reasonably select the reference voltage Vref, I, the resistance value of the load resistance module R1, the resistance value _{Rf of the} feedback resistance module connected to the positive phase input of the comparator module, and the analog output voltage of the digital-to-analog converter can be at the required level. Range.

The present invention adopts the above technical solution and has the following beneficial effects: The present invention proposes a current-steering digital-to-analog converter based on hybrid coding, which converts the digital input signal of the binary code into the high-order part of the thermometer code and the low-order part through the decoding circuit The binary code mixed coded digital control signal converts the traditional current source array with the binary multiple relationship into a current source with the same current value, and uses the mixed coded digital signal to control, due to the resistance value and current in the current source array The values are all single values, so the current mismatch of the current source array is relatively small, thereby effectively improving the conversion accuracy of the current steering type digital-to-analog converter.

Description of the drawings

Fig. 1 is a circuit structure diagram of a current steering digital-to-analog converter based on hybrid coding proposed by the present invention.

Fig. 2 is a schematic diagram of a decoding circuit involved in an embodiment of the present invention.

Fig. 3 is a circuit schematic diagram of a current steering digital-to-analog converter based on hybrid coding proposed by an embodiment of the present invention.

detailed description

The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work shall fall within the protection scope of the present invention.

In addition, the term "and/or" in this article is only an association relationship that describes associated objects, which means that there can be three relationships, for example, A and/or B, which can mean: A alone exists, and A and B exist at the same time. There are three cases of B alone. In addition, the character "/" in this text generally indicates that the associated objects before and after are in an "or" relationship.

As shown in Figure 1, a current steering digital-to-analog converter based on hybrid coding proposed by the present invention includes a decoding circuit, a current source module, a comparator module, a load resistance module and a feedback resistance module, and the input of the decoding circuit The terminal is connected to the digital input signal, the output terminal of the decoding circuit is connected to the input terminal of the current source module, the output terminal of the current source module is connected to the inverting input terminal of the comparator module, and the non-inverting input terminal of the comparator module is connected to the reference voltage Vref, the output terminal of the comparator module is connected to one end of the feedback resistance module, and the other end of the feedback resistance module is connected to the inverting input terminal of the comparator module and the load resistance module. The decoding circuit converts the digital input signal of the binary code into high bits. The mixed coded digital control signal of part thermometer code and low-order part binary code. Among them, the digital input signal of the binary code of the digital-to-analog converter is n+m bits, the low part is n bits, the high part is m bits, and n and m are natural numbers greater than or equal to 1.

As shown in Figure 2 and Figure 3, the decoding circuit converts the lower part of the n-bit binary code digital input signal of the n+m-bit binary code digital input signal into the n-bit binary code of K0, K1...Kn-1 The digital control signal converts the high-order m-bit binary code digital input signal into S1, S2···S2^m-1 2^m-1 bit thermometer code digital control signal. Convert the traditional current source array whose current value is a binary multiple relationship into a current source whose current value is a single value, and use the mixed coded digital signal of the upper part of the thermometer code and the lower part of the binary code for control, due to the resistance value and current in the current source array The values are all a single value, so that the current mismatch of the current source array is relatively small, thereby effectively improving the conversion accuracy of the digital-to-analog converter.

As shown in Figure 3, the current source module includes a current source array. The current source array includes n current sources Ii with the same current value as I. Each current source Ii is connected to one end of a corresponding switch Ki, and i is 0 to n. A natural number of -1; the current source array also includes j current sources Ij with the same current value of 2I, each current source Ij is connected to a section of the corresponding switch Sj, and j is a natural number from 1 to 2^m-1. The current source array also includes a R-2R resistor network. The resistor network includes m first resistors Ram and p second resistors Rbp. The first end of the first resistor Ram is connected to the other end of the corresponding switch Ki. The second end of the resistor Ram is connected and grounded in sequence, the second resistor Rbp is located between the first ends of two adjacent first resistors Ram, and the second resistor Rbp is connected in sequence and connected to the inverting input end of the comparator module , 0≤m≤n-1, 0≤p≤n-2; the other end of the switch Sj is connected in sequence and connected with the inverting input end of the comparator module. When m=0, the resistance value of the first resistor Ram is R; when 0<m<n, the resistance value of the first resistor Ram is 2R, 2R is the resistance value R of two series connected; the resistance of the second resistor Rbp The value is R. The gates of the switch Ki and the switch Sj constitute the input end of the current source module, and the current outflow ends of the switch Ki and the switch Sj constitute the output end of the current source module.

As shown in Figure 3, the comparator module includes a comparator based on an operational amplifier, including a non-inverting input, an inverting input, and an output. The non-inverting input is connected to the reference voltage Vref, and the inverting input is connected to the current The output end of the source module, one end of the feedback resistance module Rf, and one end of the load resistance module R1 are connected, and the output end outputs a corresponding voltage Vout. The other end of the load resistor R1 is grounded. 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, which is only used as an identification here.

The resistance value of the load resistor Rf is R, and the specific value of R needs to be specifically set according to the actual situation, which is only used as an identification here.

The above-mentioned current-steering digital-to-analog converter based on mixed coding introduces a decoding circuit to convert the digital input signal of the binary code into a high-order part of the thermometer code and the low-order part of the binary code to mix-encode a digital control signal, and convert the traditional current value into a binary multiple The current source array of the relationship is converted into current sources with the same current value, and controlled by the mixed-coded digital signal of the high-order part of the thermometer code and the low-order part of the binary code. Because the resistance value and the current value in the current source array are both a single value, the current source array The current mismatch is relatively small, thereby effectively improving the conversion accuracy of the digital-to-analog converter.

Preferably, as shown in Fig. 3, the output voltage Vout of the digital-to-analog converter is:

Among them, a reasonable selection of the values of Vref, I, R1, and R _f can keep the analog output voltage of the digital-to-analog converter in the required range.

Through the description of the above embodiments, those skilled in the art can clearly understand the inventive concept of this application. For convenience and concise description, only the division of the above-mentioned functional units is used as an example for illustration. In actual applications, it can be as required. The above-mentioned function allocation is completed by different functional units, that is, the internal structure of the device is divided into different functional units to complete all or part of the functions described above. For the specific working process of the above-described system, device, and unit, reference may be made to the corresponding process in the foregoing method embodiment, which is not repeated here.

The above are only specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed by the present invention shall be covered Within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the scope defined by the claims.

Claims

A current steering digital-to-analog converter based on hybrid coding, which is characterized in that it comprises:

Decoding circuit, the input terminal of which is connected with a binary digital signal, and the binary digital signal is converted into a mixed-coded digital control signal of the high-order part of the thermometer code and the low-order part of the binary code, and then output;

The current source module includes a current source array whose output current value is I and controlled by the low-order part of the binary code, and the current source array whose output current value is 2I and is controlled by the high-order part of the thermometer code, and the output current value is I. An R-2R network is connected between the output terminal of the source array and the ground, and the output terminals of the two power arrays are connected in parallel as the output terminal of the current source module;

Comparator module, whose non-inverting input terminal is connected to the reference voltage, and its inverting input terminal is connected to one end of the load resistance module and the output terminal of the current source module to output an analog voltage signal;

Load resistance module, the other end of which is grounded together with the current source module; and,

The feedback resistance module is connected between the inverting input terminal and the output terminal of the comparator module.
The current-steering digital-to-analog converter based on hybrid coding according to claim 1, wherein the decoding circuit converts the n-bit binary code of the lower part of the binary digital signal into K0, K1, ..., The digital control signal of the n-bit binary code of Kn-1 converts the m-bit binary code of the high-order part of the binary digital signal into S1, S2,..., S2^m-1 2^m-1 digit thermometer code number Control signal, n and m are natural numbers greater than or equal to 1.
The current-steering digital-to-analog converter based on hybrid coding according to claim 2, wherein the current source array whose output current value is I and controlled by the low-order part of the binary code comprises: n current values The current source branch of I, each current source branch is connected in series with a switch tube, and each switch tube is controlled by a bit code of the low-order part of the binary code.
The current-steering digital-to-analog converter based on hybrid coding according to claim 2, wherein the current source array whose output current value is 2I and controlled by the high-level thermometer code includes 2^m-1 channels A current source branch with a current value of 2I, each current source branch is connected in series with a switch tube, and each switch tube is controlled by a one-bit code of the high-level thermometer code.
The current-steering digital-to-analog converter based on hybrid coding according to claim 3, wherein the R-2R network includes n-1 first resistors and n-2 second resistors, the mth The first resistor is connected between the output terminal of the first current source branch and ground, and the p-th second resistor is connected between the output terminal of the p-th current source and the output terminal of the p+1-th current source, 0≤m ≤n-1, 0≤p≤n-2.
The current steering digital-to-analog converter based on hybrid coding according to claim 5, wherein when m=0, the resistance value of the first resistor is R; when 0<m<n, the first resistor The resistance value is 2R.
The current-steering digital-to-analog converter based on hybrid coding according to any one of claims 1 to 6, characterized in that according to the setting of the analog voltage signal and according to the expression

Select the reference voltage Vref input from the positive phase input terminal of the comparator module, the resistance value R1 of the load resistance module, the output current I of the current source module, and the resistance value of the feedback resistance module Rf , 0≤i<m+n.