A design method for a low-power current-steering DAC circuit with signed-bit thermometer coding
By adopting the design method of signed bit thermometer encoding in the DAC circuit, the missing code phenomenon and complex decoding problems caused by the difference in symbol weight in the high-resolution DAC are solved, and the performance of the DAC is improved and the sensor excitation current is accurately controlled. .
Patent Information
- Application Number
- CN202011542811.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2020-12-24
- Publication Date
- 2025-01-21
- Estimated Expiration
- 2040-12-24
AI Technical Summary
At high resolution, the weight difference between high-bit symbols and low-bit symbols is large, resulting in code loss. Temperature pattern DAC requires complex decoding circuits, resulting in serious circuit parasitic effects and affecting DAC performance.
A low-power current rudder DAC circuit design method with sign bit thermometer encoding is adopted. The upper 3 data bits are decoded by the thermometer, the lower 5 data bits are binary coded, and D7 is set as the sign bit Q7. Through the data bits and The sign bit switch controls the current source.
It improves the missing code phenomenon caused by the difference in symbol weight in high-resolution DAC, simplifies the decoding circuit, reduces circuit parasitic effects, improves DAC performance, and realizes the increase, decrease and precise control of the sensor excitation current through the sign bit.
Smart Images
Figure CN112688690B_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the fields of aviation, navigation and industrial control, and in particular to a design method of a low-power current steering DAC circuit with a signed bit thermometer encoding. Background Art
[0002] DAC (digital-to-analog converter) is a device that converts digital signals into analog signals (in the form of current, voltage or charge). In many digital systems (such as computers), signals are stored and transmitted digitally, and digital-to-analog converters can convert such signals into analog signals so that they can be recognized by the outside world (people or other non-digital systems).
[0003] The DACs in existing solutions mostly use binary weighted or temperature codes, which are very limited. The disadvantage of using binary weighted or thermometer code DACs is that the weights of high-order and low-order code elements of binary weighted DACs with high resolution are quite different, and may even cause missing codes. The disadvantage of thermometer code is that it requires complex decoding circuits. When the resolution increases, the circuit parasitic effects are particularly obvious, which seriously affects the performance of the DAC. Summary of the invention
[0004] In order to solve the above-mentioned technical problems existing in the background technology, the present invention provides a design method for a low-power current steering DAC circuit with a signed bit thermometer encoding, which improves the code loss phenomenon caused by the large difference in the weights of high-resolution DAC code elements and the complex decoding method brought by the temperature code, and the sign bit can realize the increase or decrease of the excitation current to the sensor, and the size of the excitation can be accurately controlled by an external digital signal.
[0005] The technical solution of the present invention is: The solution of the present invention is: The present invention is a design method of a low-power current steering DAC circuit with signed bit thermometer coding, and its special feature is that the method comprises the following steps:
[0006] 1) The upper 3 data bits D5, D6, and D7 are decoded by a thermometer, and the other lower 5 data bits D0-D4 are encoded in binary code;
[0007] 2) Set D7 to the sign bit Q7, and control the current sources 0-11 through the data bits D0-D6 and the sign bit Q7 switches.
[0008] Preferably, in step 2), data bit D0 is connected to current source 0 through a NOT gate, data bit D1 is connected to current source 1 through a NOT gate, data bit D2 is connected to current source 2 through a NOT gate, data bit D3 is connected to current source 3 through a NOT gate, and data bit D4 is connected to current source 4 through a NOT gate.
[0009] Preferably, in step 2), the sign bit Q7 is connected to the current source 5 via a NOT gate.
[0010] Preferably, in step 2), the sign bit Q7, the data bit D6 and the data bit D5 are connected to the current source 6 via a NAND gate.
[0011] Preferably, in step 2), the data bit D5, the data bit D6 and the sign bit Q7 are connected to the current source 7 through a NOR gate.
[0012] Preferably, in step 2), the sign bit Q7 and the data bit D6 are connected to the current source 8 via a NOR gate.
[0013] Preferably, in step 2), the sign bit Q7 passes through a NOT gate and the data bit D5 and the data bit D6 pass through a NAND gate, and then share an AND gate to be connected to the current source 9.
[0014] Preferably, in step 2), the sign bit Q7 and the data bit D5 pass through a NAND gate and the sign bit Q7 and the data bit D6 pass through a NAND gate, and then share an AND gate to connect to the current source 10.
[0015] Preferably, in step 2), the sign bit Q7 and the data bit D6 are connected to the current source 11 via a NAND gate.
[0016] The present invention provides a design method for a low-power current steering DAC circuit with a signed thermometer encoding, wherein the upper 3 data bits D5, D6, and D7 are decoded with a thermometer, and the other lower 5 data bits D0-D4 are encoded with a binary code; the data bit D7 is set as the sign bit Q7, and the current sources 0-11 are controlled by the data bits D0-D6 and the sign bit Q7 switches. Through the above encoding method, the problem of the weight of the low-order and high-order code elements of the DAC can be improved, so that the decoded digital logic is also relatively simple, and the D7 bit is a sign bit, so the increase or decrease of the DAC current excitation can be realized. Therefore, the present invention has the following advantages:
[0017] 1. The present invention combines the binary weighted type and the thermometer code method, improving the code loss phenomenon caused by the large difference in the weights of the high-resolution DAC code elements and the complex decoding method caused by the temperature code.
[0018] 2. In the present invention, the data bit D7 is set as the sign bit Q7. The sign bit can realize the increase or decrease of the excitation current to the sensor, and the magnitude of the excitation can be accurately controlled by an external digital signal. BRIEF DESCRIPTION OF THE DRAWINGS
[0019] Figure 1 It is a structural block diagram of the application of the method of the present invention;
[0020] Figure 2 It is a logic control diagram of data bits D0-D7 of the present invention. DETAILED DESCRIPTION
[0021] The present invention is a design method for a low-power current steering DAC circuit with signed bit thermometer coding, the method comprising the following steps:
[0022] 1) The upper 3 data bits D5, D6, and D7 are decoded by a thermometer, and the other lower 5 data bits D0-D4 are encoded in binary code;
[0023] 2) Set D7 to the sign bit Q7 (D7 is inverted to Q7), and control the current sources 0-11 through the data bits D0-D6 and the sign bit Q7 switch, where:
[0024] Data bit D0 is connected to current source 0 through a NOT gate, data bit D1 is connected to current source 1 through a NOT gate, data bit D2 is connected to current source 2 through a NOT gate, data bit D3 is connected to current source 3 through a NOT gate, data bit D4 is connected to current source 4 through a NOT gate, sign bit Q7 is connected to current source 5 through a NOT gate, sign bit Q7, data bit D6 and data bit D5 are connected to current source 6 through a NAND gate, data bit D5, data bit D6 and sign bit Q7 are connected to current source 7 through a NOR gate, sign bit Q7 and data bit D6 are connected to current source 8 through a NOR gate, sign bit Q7 passes through a NOT gate and data bit D5 and data bit D6 pass through a NAND gate, and then share an AND gate to connect to current source 9, sign bit Q7 and data bit D5 pass through a NAND gate and sign bit Q7 and data bit D6 pass through a NAND gate, and then share an AND gate to connect to current source 10, sign bit Q7 and data bit D6 are connected to current source 11 through a NAND gate.
[0025] The technical solution of the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments.
[0026] The circuit structure of the low-power 8-bit current steering DAC with signed thermometer coding in the specific example of the method of the present invention is as follows: Figure 1 As shown, the overall framework diagram is basically the same as the structure of most DACs. The 8-bit data bits D0-D7 are latched in the latch, and the switching current source 0-11 is controlled by the decoding circuit. The switching current source can be connected to the current bias. The only difference is the decoding method. The upper 3 data bits D5, D6, and D7 are decoded by the thermometer, and the other lower 5 bits D0-D5 are binary code. D7 is set to the sign bit Q7 (D7 is inverted to be Q7), and the current source is controlled by the data bits D0-D7 switches to 0-11. The data bits D7-D0 have 00000000 as the middle value, and D7 bit 1 is negative and 0 is positive, so the positive and negative correspondence is just in the form of complement code.
[0027] Table 1 shows the truth table used for decoding the upper 3 data bits.
[0028]
[0029] See also Figure 2, since binary decoding can be directly used as the switch control signal, the lower 5 bits and the upper 3 bits are combined together as the switch control signal, as follows:
[0030] Data bit D0 is connected to current source 0 through a NOT gate, data bit D1 is connected to current source 1 through a NOT gate, data bit D2 is connected to current source 2 through a NOT gate, data bit D3 is connected to current source 3 through a NOT gate, data bit D4 is connected to current source 4 through a NOT gate, sign bit Q7 is connected to current source 5 through a NOT gate, sign bit Q7, data bit D6 and data bit D5 are connected to current source 6 through a NAND gate, data bit D5, data bit D6 and sign bit Q7 are connected to current source 7 through a NOR gate, sign bit Q7 and data bit D6 are connected to current source 8 through a NOR gate, sign bit Q7 passes through a NOT gate and data bit D5 and data bit D6 pass through a NAND gate, and then share an AND gate to connect to current source 9, sign bit Q7 and data bit D5 pass through a NAND gate and sign bit Q7 and data bit D6 pass through a NAND gate, and then share an AND gate to connect to current source 10, sign bit Q7 and data bit D6 are connected to current source 11 through a NAND gate. The inversion of D7 is Q7.
[0031] After the present invention adopts this encoding method, the value of the current can be changed by adjusting the data bits D7 to D0, so that different excitations can be provided to the sensor and the size of the excitation can be adjusted within limits.
[0032] 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 aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.
Claims
1. A design method for a low-power current-steering DAC circuit with signed bit thermometer coding, characterized in that: The method comprises the following steps: 1) The upper 3 data bits D5, D6, D7 are decoded by thermometer, and the other lower 5 data bits D0-D4 are encoded by binary code; 2) Set D7 to the sign bit Q7, and the inversion of D7 is Q7. The current source (0-11) is controlled by the data bits D0-D6 and the sign bit Q7 switch, where: The data bit D0 is connected to the current source (0) through a NOT gate, the data bit D1 is connected to the current source (1) through a NOT gate, the data bit D2 is connected to the current source (2) through a NOT gate, the data bit D3 is connected to the current source (3) through a NOT gate, and the data bit D4 is connected to the current source (4) through a NOT gate; The sign bit Q7 is connected to a current source (5) through a NOT gate; the sign bit Q7, the data bit D6 and the data bit D5 are connected to a current source (6) through a NAND gate; The data bit D5, the data bit D6 and the sign bit Q7 are connected to a current source (7) via a NOR gate; The sign bit Q7 and the data bit D6 are connected to a current source (8) via a NOR gate; The sign bit Q7 passes through a NOT gate and the data bit D5 and the data bit D6 pass through a NAND gate, and then share an AND gate to connect to a current source (9); The sign bit Q7 and the data bit D5 pass through a NAND gate and the sign bit Q7 and the data bit D6 pass through a NAND gate, and then share an AND gate to connect to a current source (10); The sign bit Q7 and the data bit D6 are connected to a current source (11) via a NAND gate.