Digital-to-analog conversion system and digital-to-analog conversion method

Abstract

A digital-to-analog conversion system and a digital-to-analog conversion method, the digital-to-analog conversion system comprising: a control code conversion circuit for converting a first N-bit control code into a first Y-bit control code according to a control code conversion table, Y being greater than or equal to N; and the DAC is used for receiving the first Y-bit control code and outputting a first DAC output voltage in a plurality of DAC output voltages, and the number of the DAC output voltages is smaller than or equal to 2N.

Description

Technical Field

[0001] This invention relates to a digital-to-analog conversion system and a digital-to-analog conversion method, and particularly to a digital-to-analog conversion system and a digital-to-analog conversion method that can improve the output voltage error of a DAC (Digital to Analog Converter). Background Technology

[0002] Traditional DACs may experience output voltage errors due to manufacturing processes or other factors. For example, ideally, when a DAC receives control code CD_a, it is expected to produce a DAC output voltage V_a. However, in reality, the DAC may produce a DAC output voltage V_b instead. This situation is called DAC output voltage error. All control codes may have this problem. As a result, circuits that operate based on the DAC output voltage may generate significant noise. This is more pronounced when the DAC's circuit area is small. Summary of the Invention

[0003] One object of the present invention is to provide a digital-to-analog conversion system that can improve the output voltage error of a DAC.

[0004] Another objective of this invention is to provide a digital-to-analog conversion method that can improve the output voltage error of a DAC.

[0005] One embodiment of the present invention discloses a digital-to-analog conversion system, comprising: a control code conversion circuit for converting a first N-bit control code into a first Y-bit control code according to a control code conversion table, wherein Y is greater than or equal to N; and a DAC for receiving the first Y-bit control code and outputting a first DAC output voltage from a plurality of DAC output voltages, wherein the number of such DAC output voltages is less than or equal to 2. N .

[0006] Another embodiment of the present invention discloses a digital-to-analog conversion method, comprising: converting a first N-bit control code into a first Y-bit control code according to a control code conversion table, where Y is greater than or equal to N; receiving the first Y-bit control code with a DAC and outputting a first DAC output voltage from a plurality of DAC output voltages, wherein the number of these DAC output voltages is less than or equal to 2. N .

[0007] According to the foregoing embodiments, the control code can be converted using a control code conversion table to make the DAC output voltage close to the desired output voltage, thereby improving the DAC output voltage error problem in known technologies. Attached Figure Description

[0008] Figure 1A schematic diagram illustrating how to compensate for DAC output voltage errors is shown.

[0009] Figure 2 Block diagrams of digital-to-analog conversion systems according to different embodiments of the present invention are depicted.

[0010] Figures 3 to 6 A schematic diagram illustrating the operation of a digital-to-analog conversion system according to different embodiments of the present invention is provided.

[0011] Figure 7 A flowchart illustrating the creation of a control code conversion table according to an embodiment of the present invention is described.

[0012] Figure 8 A flowchart illustrating a digital-to-analog conversion method according to an embodiment of the present invention is provided. Detailed Implementation

[0013] The present invention will be described below with reference to several embodiments. Please note that the terms "first," "second," and similar descriptions used in the following description are only used to define different elements, parameters, data, signals, or steps, and are not intended to limit their order. For example, the first device and the second device may be devices with the same structure but different from each other.

[0014] Figure 1 A schematic diagram illustrating how to compensate for DAC output voltage errors is shown. Figure 1 In the original design, the DAC was expected to generate an output voltage V_1 upon receiving control code CD_1, based on the ideal conversion curve. However, in reality, the DAC generates an output voltage V_2 upon receiving control code CD_1, according to the actual conversion curve. This results in a voltage difference of V_2 - V_1 between the DAC output voltage corresponding to control code CD_1. This situation is what is referred to as the "DAC output voltage error." To compensate for this error, the control code is first converted into another control code, so that the DAC outputs a voltage closest to the originally desired output voltage based on the actual conversion curve, corresponding to the converted control code.

[0015] For example, in Figure 1 In this embodiment, the required output voltage is the DAC output voltage V_1. Therefore, before the DAC receives the control code, it first converts the control code CD_1 into the control code CD_11. Then, the DAC outputs the corresponding DAC output voltage V_3 based on the actual conversion curve. The DAC output voltage V_3 is the DAC output voltage closest to the required output voltage V_1 among all DAC output voltages generated by all control codes according to the actual conversion curve. All control codes can be converted according to this rule.

[0016] Based on the above Figure 1Based on the concept, this invention provides a digital-to-analog conversion system that can convert control codes. Figure 2 Block diagrams of digital-to-analog conversion systems according to different embodiments of the present invention are depicted. Figure 2 In Examples 1, 2, and 3, the digital-to-analog conversion system 200 all includes a control code conversion circuit 201 and a DAC 203. The control code conversion circuit 201 may be implemented in hardware (e.g., a circuit or device) or software (e.g., executed by processing circuitry). In Example 1, the control code conversion circuit 201 converts an N-bit control code into an N-bit control code according to a control code conversion table; therefore, the DAC 203 outputs one of multiple DAC output voltages based on the received control code. The number of these multiple DAC output voltages is less than or equal to 2. N In Example 2, the control code conversion circuit 201 converts the N-bit control code into an M-bit control code according to the control code conversion table, where M is greater than N. Therefore, the DAC 203 will have 2... M There are 2 candidate output voltages. DAC 203 will select from 2 M The candidate output voltage is selected from the two closest to the original. N 2 of the required output voltage N Each DAC outputs a voltage. Therefore, DAC 203 will output 2 based on the received control code. N One of the DAC output voltages. Also note that in Example 2, 2 M The candidate output voltages only appear when the control code conversion table is generated. During normal operation, the DAC 203 outputs the last selected 2... N One of the DAC output voltages.

[0017] In Example 3, the control code conversion circuit 201 converts the N-bit control code into an M+A-bit control code according to the control code conversion table. In this case, the M-bit control code is the main control code and the A-bit sub-control code is the sub-control code, where A is a positive integer. The main control code is used to generate the main voltage, and the sub-control code is used to generate the sub-voltage. DAC 203_1 will still have 2 M There are 2 candidate output voltages, but these 2 M Each candidate output voltage can be formed by adding a secondary voltage to the main voltage, while in Example 2 it is formed only by the main voltage. In Example 3, DAC 203_1 will form the output voltage according to 2... M The primary voltage is selected from the candidate output voltages, and then the secondary voltage is generated based on the A-bit secondary control code. This is then used to generate 2... N The DAC outputs a voltage. Then, DAC 203 will output 2 according to the control code. N One of the DAC output voltages. Details regarding each example will be provided below.

[0018] Figures 3 to 6Schematic diagrams illustrating the operation of digital-to-analog conversion systems according to different embodiments of the present invention are provided. Figures 3 to 6 In this embodiment, only a few required output voltages and DAC output voltages are given for illustration. However, the number of required output voltages and DAC output voltages is not limited to this. Figures 3 to 6 The quantity in. Figure 3 correspond Figure 2 Example 1 in the example. Figure 3 In this embodiment, the DAC output voltages V_N1, V_N2, and V_N3 are the required output voltages of the N-bit control codes CD_1, CD_2, and CD_3 received by the corresponding control code conversion circuit 101. The DAC output voltages V_N1T, V_N2T, and V_N3T are the output voltages of the DAC 103 corresponding to the N-bit control codes CD_1, CD_2, and CD_3, and are calculated according to... Figure 1 The DAC output voltage generated by the actual conversion curve in the curve.

[0019] exist Figure 3 In this embodiment, the conversion relationship of the N-bit control code is determined based on the relationship between the required output voltage and the closest DAC output voltage. For example, if the required output voltage V_N1 is closest to the DAC output voltage V_N2T, the control code conversion circuit 101 will convert the received N-bit control code CD_1 into the N-bit control code CD_2 corresponding to the DAC output voltage V_N2T. As another example, if the required output voltage V_N4 is closest to the DAC output voltage V_N5T, the control code conversion circuit 101 will convert the received N-bit control code CD_4 into the N-bit control code CD_5 corresponding to the DAC output voltage V_N5T. Please also note that in... Figure 3 Different required output voltages can correspond to the same DAC output voltage. For example, the voltage difference between the DAC output voltage V_N3T and the required output voltages V_N2 and V_N3 is the same, but the voltage difference between the DAC output voltage V_N4T and the required voltage V_N3 is quite large. Therefore, in this case, the required output voltages V_N2 and V_N3 will both correspond to the DAC output voltage V_N3T. That is, the control code CD_2 corresponding to the required output voltage V_N2 and the control code CD_3 corresponding to the required output voltage V_N3 will both be converted into the control code CD_3 corresponding to the DAC output voltage V_N3T.

[0020] In addition, Figure 3 In some embodiments, some DAC output voltages differ significantly from the required voltage and therefore do not correspond to any of the converted control codes, nor are they output by DAC 103. For example, DAC output voltages V_N1T and V_N4T do not correspond to any of the converted control codes, and therefore will not be output by DAC 103. Based on the foregoing, because... Figure 3The DAC output voltage and the required output voltage are not necessarily in a one-to-one correspondence, and some DAC output voltages will not be used. Therefore, the control code conversion circuit 101 receives 2 N An N-bit control code may cause the total number of DAC output voltages to equal 2. N One or less than 2 N One. The aforementioned. Figure 3 In the embodiment, DAC 201 receives all 2 bits generated by the converted N-bit control code. N Each voltage can be considered a candidate output voltage, but the final output voltage from the DAC is the DAC output voltage.

[0021] Figure 4 correspond Figure 2 Example 2, specifically the control code conversion circuit 201, converts an N-bit control code into an M-bit control code. Figure 4 In the diagram, DAC output voltages V_N1, V_N2, and V_N3 are the required output voltages for the corresponding N-bit control codes CD_1, CD_2, and CD_3. DAC output voltages V_M1, V_M2, V_M3, V_M4, V_M5, and V_M6 are the output voltages for the corresponding M-bit control codes CD_1M, CD_2M, CD_3M, CD_4M, CD_5M, and CD_6M of the DAC 103, based on... Figure 1 The candidate output voltage is generated from the actual conversion curve in the circuit. The DAC 103 will generate 2 based on all M-bit control codes. M There are 2 candidate output voltages. Since M is greater than N, the number of candidate output voltages is 2. M It will also be greater than the number of required output voltages by 2. N .

[0022] Next, we will start from 2 M Select the closest 2 from the candidate output voltages. N 2 of the required output voltage N The system uses candidate output voltages as the DAC output voltage and converts the control code accordingly. For example, if the candidate output voltage closest to the desired output voltage V_N1 is V_M2, then V_M2 will be used as the DAC output voltage, and the control code conversion circuit 201 will convert the control code CD_1 corresponding to the desired output voltage V_N1 into the control code CD_2M corresponding to the candidate output voltage V_M2. Similarly, if the candidate output voltage closest to the desired output voltage V_N2 is V_M4, then V_M4 will be used as the DAC output voltage, and the control code conversion circuit 201 will convert the control code CD_2 corresponding to the desired output voltage V_N2 into the control code CD_4M corresponding to the candidate output voltage V_M4. Figure 4 In the embodiment, since the number of candidate output voltages is 2 M It will be greater than the number of required output voltages by 2.N For each desired output voltage, a relatively close candidate output voltage can be found, therefore the desired output voltage and the DAC output voltage can have a one-to-one correspondence. In this case, the number of DAC output voltages that DAC 103 can ultimately output and the number of desired output voltages can both be 2. N indivual.

[0023] Figure 5 correspond Figure 2 In Example 3, the control code conversion circuit 201 converts the N-bit control code into an M+A-bit control code, which is an M-bit main control code and an A-bit secondary control code. A is a positive integer. Figure 5 In this embodiment, it is 1. Furthermore, DAC 203_1 has one more secondary voltage circuit than DAC 203. In one embodiment, the DAC output voltage of DAC 203 is generated based on the current supplied by a current source; therefore, the secondary voltage circuit can also be a current source, and its circuit area determines the maximum value of the secondary voltage it can generate. DAC 203_1 generates the main voltage according to the M-bit main control code and... Figure 4 The method for generating candidate output voltages based on the M-bit control code is the same. For example, in Figure 5 In this circuit, DAC 203_1 generates main voltages V_M1 and V_M2 based on the M-bit main control codes CD_1M and CD_2M, respectively. The A-bit secondary control code determines whether the secondary voltage circuit provides a secondary voltage. By combining the main and secondary voltages, DAC 203_1 can map the desired output voltage to a more closely approximate DAC output voltage.

[0024] For example, in Figure 5 In the embodiment, the required output voltage V_N1 corresponding to control code CD_1 falls exactly between the candidate output voltages V_M2 and V_M3. Therefore, regardless of whether control code CD_1 is converted to control code CD_1M or CD_2M, the required output voltage V_N1 will have a large output voltage error. In this case, a secondary control code can be used to enable the secondary voltage circuit to provide a secondary voltage, so that the required output voltage V_N1 corresponds to the DAC output voltage V_M3' after adding the secondary voltage V_A1 to the candidate output voltage V_M3, which can reduce the output voltage error of the required output voltage V_N1. In this case, the control code conversion circuit 201 will convert control code CD_1 into control code (CD_3M+A1). The main control code CD_3M determines the value of the main voltage V_M3, while the secondary control code A1 indicates that the secondary voltage circuit will provide a secondary voltage. In addition, in Figure 5 In this embodiment, other control codes are also converted into M+A bit control codes. For example, control code CD_3 will be converted into control code (CD_6M+A2), where the main control code CD_6M determines the value of the main voltage as V_M6, and the secondary control code A2 indicates that the secondary voltage circuit will not provide a secondary voltage.

[0025] exist Figure 5 In the embodiment, if DAC 203_1 receives M-bit master control codes with M different bit values, it will generate 2... M There are two main voltages. Adjacent main voltages, that is, the closest main voltages, will have a voltage difference. For example, there will be a voltage difference between main voltages V_M2 and V_M3, and a voltage difference between main voltages V_M3 and V_M4. Figure 5 In this embodiment, the secondary voltage will be less than this voltage difference. Also note that different adjacent primary voltages may have different voltage differences. In this case, the secondary voltage may be less than the smallest of all the different voltage differences.

[0026] exist Figure 5 In one embodiment, the secondary voltage is used to allow the desired output voltage to more accurately correspond to the DAC output voltage; in this case, the secondary voltage can be designed to be no greater than the voltage difference. However, in another embodiment, the secondary voltage can be used to increase the swing of the DAC output voltage. For example... Figure 6 As shown, the main voltage V_M1 is the largest of all main voltages, but it is still less than the required output voltage V_N1. In this case, a secondary voltage V_A1 can be added to the main voltage V_M1 to generate the DAC output voltage V_M1'. In this case, the required output voltage V_1N can be mapped to the DAC output voltage V_M1', that is, the control code CD_1 is converted into an M+A bit control code (CD_M1+A1). The main control code CD_M1 determines the main voltage V_M1, while the secondary control code A1 represents that the secondary voltage circuit will generate the secondary voltage V_A1. Figure 6 In this embodiment, the secondary voltage can be selected as a relatively large value, for example, greater than the voltage difference of the aforementioned primary voltage. Furthermore, in... Figure 6 In this embodiment, other control codes are also converted into M+A bit control codes. For example, control code CD_2 will be converted into control code (CD_M2+A2), where the main control code CD_2M determines the value of the main voltage V_M2, and the secondary control code A2 indicates that the secondary voltage circuit will not provide a secondary voltage.

[0027] According to the foregoing embodiments, Figure 2 The digital-to-analog conversion system can be briefly described as follows: a control code conversion circuit, used to convert a first N-bit control code into a first Y-bit control code according to a control code conversion table, where Y is greater than or equal to N; and a DAC, used to receive the first Y-bit control code and output the first DAC output voltage from a plurality of DAC output voltages. The number of the plurality of DAC output voltages can be less than or equal to 2. N .

[0028] In Example 1, Y = N. In the corresponding... Figure 3In this embodiment, the control code conversion circuit 101 converts the N-bit control code CD_2 (first N-bit control code) into an N-bit control code CD_3 (first Y-bit control code). The DAC 203 then outputs the corresponding DAC output voltage V_N3T (first DAC output voltage) based on the control code CD_3. In Example 2, Y = M. In the corresponding... Figure 4 In this embodiment, the control code conversion circuit 101 converts the N-bit control code CD_1 (first N-bit control code) into an M-bit control code CD_2M (first Y-bit control code). The DAC 203 then outputs the corresponding DAC output voltage V_M2 (first DAC output voltage) based on the control code CD_2M. In Example 3, Y = M + A. In the corresponding... Figure 5 In this embodiment, the control code conversion circuit 101 converts the N-bit control code CD_1 (first N-bit control code) into an M+A-bit control code CD_3M+A1 (first Y-bit control code). The DAC 203 then outputs the corresponding DAC output voltage V_M3' (first DAC output voltage) according to the control code CD_3M+A1.

[0029] In one embodiment, if the DAC receives an unconverted first N-bit control code, it will generate a second DAC output voltage that is different from the first DAC output voltage. Figure 4 For example, if DAC 203 receives the unconverted control code CD_1 (the first N-bit control code) instead of the converted control code CD_2M, it will generate a DAC output voltage (the second DAC output voltage) that is different from the DAC output voltage V_M2 (the first DAC output voltage). Therefore, if the control code CD_1 is received directly by DAC 203 without conversion, the required output voltage V_N1 corresponding to the control code CD_1 will have a large output voltage error.

[0030] The DAC can also perform similar actions when receiving other control codes. In one embodiment, the control code conversion circuit 201 converts the second N-bit control code into a second Y-bit control code according to a control code conversion table. For example, in... Figure 4 In this embodiment, the N-bit control code CD_2 is converted into the M-bit control code CD_4M. After receiving the second Y-bit control code, the DAC outputs a third DAC output voltage; for example, after receiving the control code CD_4M, the DAC outputs a DAC output voltage V_M4. If the DAC receives the second N-bit control code, it will generate a fourth DAC output voltage that is different from the third DAC output voltage. For example, if the DAC receives the unconverted control code CD_2, it will generate a fourth DAC output voltage that is different from the DAC output voltage V_M4.

[0031] As mentioned earlier, the control code conversion circuit 101 converts control codes according to a control code conversion table. This control code conversion table can be established in various ways. Figure 7 A flowchart illustrating the establishment of a control code conversion table according to an embodiment of the present invention is described, which includes the following steps:

[0032] Step 701

[0033] All N-bit control codes that have not been converted by the control code conversion circuit 101 are input into the DAC to obtain all DAC output voltages for calculation. Figure 1 The actual conversion curve shown.

[0034] Step 703

[0035] To obtain all Y-bit control codes, we get 2. Y Each Y-bit control code is input into the DAC to obtain the 2^Y control codes corresponding to all Y-bit control codes through the actual conversion curve. Y One candidate output voltage.

[0036] In other words, the DAC output voltage corresponding to the Y-bit control code is obtained from the actual conversion curve. As mentioned earlier, Y can be N, M, or M+A. The Y-bit control code can be a pre-set set of codes, a code input during DAC calibration, or a set of continuous codes determined by the software.

[0037] Step 705

[0038] Align the maximum N-bit control code (Cmax) with the maximum value and the minimum N-bit control code (Cmin) with the minimum value with the maximum voltage (Vmax) and minimum voltage (Vmin) that the DAC can output, respectively.

[0039] Step 707

[0040] The voltage between Vmax and the minimum voltage Vmin in step 705 is distributed to the N-bit control code other than Cmax and Cmin in an equal voltage difference manner to obtain the desired output voltage.

[0041] In detail, all N-bit control codes minus Cmax and Cmin will have 2 N - 2 N-bit control codes. The two closest N-bit control codes will have a control code interval of 2. N There will be 2 N-bit control codes. N -1 control code interval. Therefore, the voltage difference of the DAC output voltage corresponding to the two closest N-bit control codes will be...

[0042] For example, if N=3, there are a total of 8 N-bit control codes. Subtracting Cmax and Cmin, there are 6 N-bit control codes. The two closest N-bit control codes will have a control code interval, resulting in 7 intervals for the 8 N-bit control codes. Therefore, the voltage difference between the DAC output voltages corresponding to the two closest N-bit control codes will be...

[0043] Based on this rule, all the required output voltages can be obtained.

[0044] Step 709

[0045] Find the candidate output voltages that are closest to the required output voltage, and establish the conversion relationship of the control code accordingly.

[0046] The rules governing the conversion of control codes have been detailed above. Figures 2 to 6 The specific implementation is not described in detail here.

[0047] Based on the foregoing embodiments, a digital-to-analog conversion method can be obtained. Figure 8 A flowchart illustrating a digital-to-analog conversion method according to an embodiment of the present invention is shown, comprising the following steps:

[0048] Step 801

[0049] According to the control code conversion table, the first N-bit control code is converted into the first Y-bit control code, where Y is greater than or equal to N.

[0050] Step 803

[0051] The DAC receives the first Y-bit control code and outputs the first DAC output voltage from a plurality of DAC output voltages, wherein the number of these DAC output voltages is less than or equal to 2. N .

[0052] The other steps have been disclosed in the foregoing embodiments, and therefore will not be repeated here.

[0053] According to the foregoing embodiments, the control code can be converted using a control code conversion table to make the DAC output voltage close to the desired output voltage, thereby improving the DAC output voltage error problem in known technologies.

[0054] The above description is only a preferred embodiment of the present invention. All equivalent changes and improvements made in accordance with the scope of the claims of the present invention should be included in the scope of the present invention.

[0055] Explanation of reference numerals in the attached figures:

[0056] 200 Digital-to-Analog Conversion System

[0057] 201 Control Code Conversion

[0058] 203,203_1DAC

Claims

1. A digital-to-analog conversion system, comprising: A control code conversion circuit is used to convert a first N-bit control code into a first Y-bit control code, where Y is greater than or equal to N, according to a control code conversion table; and A DAC is used to receive the first Y-bit control code and output the first DAC output voltage from a plurality of DAC output voltages, wherein the number of these DAC output voltages is less than or equal to 2. N .

2. In the digital-to-analog conversion system as described in claim 1, if the DAC receives the first N-bit control code, it will generate a second DAC output voltage that is different from the first DAC output voltage.

3. The digital-to-analog conversion system as described in claim 2, The control code conversion circuit converts the second N-bit control code into the second Y-bit control code according to the control code conversion table. The DAC receives the second Y-bit control code and outputs the third DAC output voltage from these DAC output voltages; If the DAC receives the second N-bit control code, it will generate a fourth DAC output voltage that is different from the output voltage of the third DAC.

4. The digital-to-analog conversion system as described in claim 1, wherein the first Y-bit control code includes an M-bit main control code and an A-bit secondary control code, the DAC generates a main voltage based on the M-bit main control code and generates a secondary voltage based on the A-bit secondary control code, and then adds the main voltage and the secondary voltage to generate the first DAC output voltage.

5. The digital-to-analog conversion system as described in claim 4, wherein if the DAC receives M different bit values ​​of the M-bit master control code, it will generate a 2... M A primary voltage, wherein the secondary voltage is less than the voltage difference between adjacent primary voltages.

6. The digital-to-analog conversion system as described in claim 4, wherein if the DAC receives M different bit values ​​of the M-bit master control code, it will generate a 2... M A primary voltage, wherein the secondary voltage is greater than the voltage difference between adjacent primary voltages.

7. The digital-to-analog conversion system as described in claim 4, wherein A is 1.

8. The digital-to-analog conversion system as claimed in claim 1, wherein the control code conversion table is generated through the following steps: Multiple N-bit control codes are input into the DAC to calculate the actual conversion curve; Get 2 Y Each Y-bit control code, and through this actual conversion curve, all corresponding 2... Y Candidate output voltages for each Y-bit control code; Align the largest N-bit control code and the smallest N-bit control code in these N-bit control codes with the maximum and minimum voltages that the DAC can output, respectively. The voltage between the maximum voltage and the minimum voltage is distributed to these N-bit control codes other than the maximum N-bit control code and the minimum N-bit control code in an equal voltage difference manner to obtain multiple desired output voltages; Find the candidate output voltages that are closest to the required output voltages, and establish the conversion relationship of the control code accordingly.

9. A digital-to-analog conversion method, comprising: According to the control code conversion table, the first N-bit control code is converted into the first Y-bit control code, where Y is greater than or equal to N; The DAC receives the first Y-bit control code and outputs the first DAC output voltage from a plurality of DAC output voltages, wherein the number of these DAC output voltages is less than or equal to 2. N .

10. The digital-to-analog conversion method as described in claim 9, wherein if the DAC receives the first N-bit control code, it will generate a second DAC output voltage that is different from the first DAC output voltage.

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