CN106341130A - Digital-to-analog converter - Google Patents

Abstract

The invention provides a digital-to-analog converter, and is used to convert input digital signals into analog signals. The digital-to-analog converter comprises a first-level resistor string structure, a decoder, a first single voltage selector, a second single voltage selector, a second-level resistor string structure and a third single voltage selector at least; the first-level resistor string structure comprises first-level resistors and switches in serial connection at least, and the first-level resistors and the switches are arranged separately; the decoder is connected with the first-level resistor string structure; the first single voltage selector is connected with the first-level resistor string structure; the second single voltage selector is connected with the first-level resistor string structure; the second-level resistor string structure is connected with the first single voltage selector and the second single voltage selector, and comprises second-level resistors in serial connection; and the third single voltage selector is connected with the second-level resistors in serial connection. The digital-to-analog converter is simple in structure, low in power consumption, small in area and high in precision; and compared with the prior art, the area and power consumption are reduced, and errors are reduced greatly.

Description

Digital to analog converter

Technical field

The present invention relates to technical field of integrated circuits, more particularly to a kind of digital to analog converter.

Background technology

The real world is made up of analog quantity, digital to analog converter (digital-to-analog converter, Dac it is) most important ingredient in hybrid digital-analog integrated circuit, its effect converts digital signals into real world Analogue signal.Dac is essential as the interface device of numeral and simulation, more and more applied in signals collecting and In the middle of process, digital communication, Automatic Detection and Control and multimedia technology.The performance (area, power consumption, precision, speed etc.) of dac is straight Connect the quality having influence on whole system and performance.

Traditional dac structure is single-stage resistance string dac (resistor-string dac), abbreviation rdac, as shown in figure 1, Input signal is passed through to control n position voltage selecting switch array to select corresponding reference voltage from overall resistance string, realizes numeral To the conversion of analogue signal, the advantage of rdac is that structure is simple and monotonicity is good to signal, but is as the raising of precision, its voltage The number of switches of selecting switch array is in exponential increase, and chip area also sharply increases therewith, and the dac of therefore this structure is uncomfortable For high-precision applications occasion.

In order to solve the above problems, the dac of some two-layer configurations is suggested, and such as Fig. 2 (a) show a kind of typical two Level resistance string dac, dac is divided into two-stage by this structure, and the usual first order, using using overall resistance string structure, is selected by voltage Select device and select two adjacent voltages from overall resistance string, then the second level by resistance string partial pressure, the first order is obtained two Individual neighboring voltage carries out accurate partial pressure, obtains final analog voltage；Wherein, in order to reduce second level resistance string to first order electricity The load effect of resistance string, this structure inserts two unity gain buffers between two-stage resistance string.In addition, document " a 10- bit resistor-floating-resistor-string dac(rfr-dac)for high color-depth lcd Driver ics " (c.-w.lu, p.-y.yin, c.-m.hsiao, m.-c.f.chang and y.-s.lin etc., ieee J.solid-state circuits, vol.47, no.10, pp.2454 2466, oct.2012) in propose one kind Resistor-floating-resistor-string dac (rfr-dac), such as shown in Fig. 2 (b), this dac is also adopted by two-stage electricity Resistance string structure, the first order realizes the selection of neighboring voltage, and accurate partial pressure is realized by resistance string in the second level, with Fig. 2 (a) structure not With this structure dac inserts two an equal amount of current sources so that the second level is electric in the upper and lower ends of second level resistance string All nodes of resistance string all present high-impedance behavior, thus greatly reducing the load effect of second level resistance string, improve The precision of dac.

Above two two-stage resistance string dac, compared with traditional single stage resistance string dac, reduces chip area, but there is also Some shortcomings, in two-stage dac as shown in for Fig. 2 (a), delay due to inserting two unit gains in the middle of two-stage resistance string Rush device so that circuit power consumption increases, simultaneously as process mismatch, unity gain buffer can have offset error, and then makes Dac also produces error；For the two-layer configuration dac in Fig. 2 (b), above-mentioned document during implementing, adopt by two current sources It is the current-mirror structure current source of mos pipe composition, because mos pipe has channel-length modulation, therefore two electric currents The size in source can be affected by first order resistance string output voltage so that the precision of this structure two-stage resistance string dac reduces.

Therefore, traditional single stage resistance string dac improves with precision, and area index increases, and not being suitable for high accuracy should With.Compared with single-stage resistance string dac, although the area of two-stage resistance string dac of same precision substantially reduces, two-layer configuration The isolation circuit in order to reduce second level resistance string, the load effect of first order resistance string being introduced in dac can affect dac Precision.Therefore, how to optimize dac structure further so as to improve precision as far as possible while reducing area, be urgently to solve Problem certainly.

Content of the invention

The shortcoming of prior art in view of the above, it is an object of the invention to provide a kind of digital to analog converter, for solving Certainly in prior art, single-stage resistance string dac improves with precision, and area index increases, and is not suitable for high-precision applications, and two Level resistance string dac can affect to reduce the isolation circuit that second level resistance string introduces on the load effect of first order resistance string The problem of the precision of dac.

For achieving the above object and other related purposes, the present invention provides a kind of digital to analog converter, for will input number Word signal is converted to analogue signal, and wherein, described digital to analog converter at least includes:

First order resistance string structure, it at least includes the multiple first order resistance being connected in series and multiple switch, and described Stage resistive and the arrangement of described switch gap；

Decoder, is connected with described first order resistance string structure, for the high position control based on described supplied with digital signal, Output multiple control signal, to control the opening and closing of each switch in described first order resistance string structure；

First univoltage selector, is connected with described first order resistance string structure, for based on described supplied with digital signal High-order control, select first order output voltage from described first order resistance string structure；

Second univoltage selector, is connected with described first order resistance string structure, for based on described supplied with digital signal High-order control, select the second level output adjacent with described first order output voltage electric from described first order resistance string structure Pressure；

Second level resistance string structure, is connected with described first univoltage selector, described second univoltage selector respectively, It at least includes the multiple second level resistance being connected in series, for described first order output voltage and the described second level are exported electricity Pressure carries out accurate partial pressure；

3rd univoltage selector, is connected with described second level resistance string structure, for based on described supplied with digital signal Low level control, from the resistance string structure of the described second level select output voltage, as described digital to analog converter output simulation Voltage.

Preferably, described supplied with digital signal is n position, and the low level of described supplied with digital signal is m position, described input numeral A high position for signal is n-m position, and described first order resistance and described switch are 2^n-mIndividual, described second level resistance is 2^mIndividual and full Sufficient equation below:

$r_{\min or}=\frac{r_{main}}{2^m};$

Wherein, r_mainFor the resistance of described first order resistance, r_minorFor the resistance of described second level resistance, n is more than 1 Natural number, m is the natural number less than n.

Preferably, described decoder has 2^n-mIndividual control signal outfan, for output 2^n-mIndividual described control signal, institute State the 2 of decoder^n-mIndividual control signal outfan and 2^n-mIndividual described switch connects one to one.

Preferably, the 2 of described decoder output^n-mIndividual described control signal controls theIndividual described switch is beaten Open, remaining described switch cuts out；Wherein, b_i+mThe i-th+m position signal for described supplied with digital signal.

Preferably, in described first order resistance string structure, one end of the 1st described switch connects high reference level, separately One end connects the 1st described first order resistance, and the 2nd^n-mOne end of individual described first order resistance connects the 2nd^n-mIndividual described switch, separately One end connects low datum, remaining described first order resistance and remaining described switch string in the way of spaced one by one Connection connects.

Preferably, described first univoltage selector and described second univoltage selector are respectively provided with 2^n-mIndividual datum Input and a datum outfan, the 2 of described first univoltage selector^n-mIndividual datum input corresponds It is connected to 2^n-mThe high-pressure side of individual described switch, the 2 of described second univoltage selector^n-mIndividual datum input corresponds It is connected to 2^n-mThe low-pressure end of individual described first order resistance, the datum outfan of described first univoltage selector is for defeated Go out described first order output voltage, the datum outfan of described second univoltage selector is used for exporting the described second level defeated Go out voltage, the magnitude of voltage of described first order output voltage is more than the magnitude of voltage of described second level output voltage, and meet public as follows Formula:

$v_h=\frac{v_{refh}-v_{refl}}{2^{n-m}}(1+\underset{i=0}{\overset{n-m-1}{\σ}}{2}^i{b}_{i+m})+v_{refl},$

$v_l=\frac{v_{refh}-v_{refl}}{2^{n-m}}\underset{i=0}{\overset{n-m-1}{\σ}}{2}^i{b}_{i+m}+v_{refl};$

Wherein, v_hFor the magnitude of voltage of described first order output voltage, v_lFor the magnitude of voltage of described second level output voltage, v_refhFor described high reference level, v_reflFor described low datum, b_i+mThe i-th+m position signal for described supplied with digital signal.

Preferably, in the resistance string structure of the described second level, 2^mIndividual described second level resistance is sequentially connected in series；Wherein, 1st described second level resistance is also connected with described first order output voltage, and the 2nd^mIndividual described second level resistance is also connected with described Two grades of output voltages.

Preferably, described 3rd univoltage selector has 2^mIndividual datum input and a datum output End, the 2 of described 3rd univoltage selector^mIndividual datum input connects one to one 2^mIndividual described second level resistance Low-pressure end, the datum outfan of described 3rd univoltage selector is used for exporting the output simulation electricity of described digital to analog converter Pressure, and meet equation below:

$v_{out}=\frac{v_h-v_l}{2^m}\underset{i=0}{\overset{m-1}{\σ}}{2}^i{b}_i+v_l=\frac{v_{refh}-v_{refl}}{2^n}\underset{i=0}{\overset{n-1}{\σ}}{2}^i{b}_i+v_{refl};$

Wherein, v_outFor the output analog voltage of described digital to analog converter, v_hVoltage for described first order output voltage Value, v_lFor the magnitude of voltage of described second level output voltage, v_refhFor described high reference level, v_reflFor described low datum, b_i I-th bit signal for described supplied with digital signal.

Preferably, described first univoltage selector, described second univoltage selector and described 3rd univoltage select Device is tree-like, fully decoded, two-dimension addressing or three-dimensional addressing form univoltage selecting switch array.

Preferably, described decoder is tree-like, two-dimension addressing or the switch arrays decoder of three-dimensional addressing form.

As described above, the digital to analog converter of the present invention, have the advantages that present configuration is simple, low in energy consumption, face Long-pending little, and there is high accuracy.Specifically, compared with traditional two-stage resistance string dac of prior art, the tradition two of prior art Level resistance string dac needs to increase by two unity gain buffers between two-stage resistance string, thus eliminating second level resistance string Load effect to first order resistance string, on the one hand this increase power consumption and area, and on the other hand above all unit gain is delayed The offset voltage rushing device can introduce error for digital to analog converter；And the present invention only need to increase by one in first order resistance string structure is Row switch and control the decoder of these switches so that second level resistance string structure and first order resistance string structure are with input Digital signal be not in different series connection together it is allowed to the electric current of first order resistance string structure flows through second level resistance string knot Structure, thus eliminating the unity gain buffer between two-stage resistance string, reducing area and power consumption, greatly reducing error. In addition, compared with another kind of resistance string dac of prior art, another kind of resistance string dac of prior art needs in second level electricity Increase by two current-mirror structure current sources being made up of mos pipe in resistance string, because mos pipe has channel-length modulation, because The size of this two current sources can be affected by first order resistance string output voltage, causes this two-stage resistance string dac final Output analog voltage is also affected, so that the precision of this two-stage resistance string dac reduces；And the invention enables the second level is electric Resistance string structure can form with first order resistance string structure and be connected in series it is allowed to the electric current of first order resistance string structure flows through second Level resistance string structure, thus eliminate in the resistance string of the second level two current sources of increase, it is to avoid final output simulation electricity Pressure is affected it is ensured that the high accuracy of digital to analog converter.

Brief description

Fig. 1 is shown as the structural representation of present invention single-stage of the prior art resistance string dac.

Fig. 2 (a) is shown as a kind of present invention structural representation of two-stage resistance string dac of the prior art.

Fig. 2 (b) is shown as the structural representation of present invention another kind of the prior art two-stage resistance string dac.

Fig. 3 is shown as the structural representation of the digital to analog converter of first embodiment of the invention and second embodiment.

Fig. 4 is shown as the principle schematic of the digital to analog converter of second embodiment of the invention.

Fig. 5 is shown as the transmission curve emulation schematic diagram of the digital to analog converter of second embodiment of the invention.

Fig. 6 is shown as the integral nonlinearity curve emulation schematic diagram of the digital to analog converter of second embodiment of the invention.

Fig. 7 is shown as the differential nonlinearity curve emulation schematic diagram of the digital to analog converter of second embodiment of the invention.

Component label instructions

1 first order resistance string structure

2 decoders

3 first univoltage selectores

4 second univoltage selectores

5 second level resistance string structures

6 the 3rd univoltage selectores

Specific embodiment

Below by way of specific instantiation, embodiments of the present invention are described, those skilled in the art can be by this specification Disclosed content understands other advantages and effect of the present invention easily.The present invention can also be by addition different concrete realities The mode of applying is carried out or applies, and the every details in this specification can also be based on different viewpoints and application, without departing from Carry out various modifications and changes under the spirit of the present invention.

Refer to Fig. 3, first embodiment of the invention is related to a kind of digital to analog converter, for turning the digital signal of input It is changed to analogue signal.It should be noted that the diagram provided in present embodiment only illustrates the base of the present invention in a schematic way This conception, then in schema only display and relevant assembly in the present invention rather than according to component count during actual enforcement, shape and Size is drawn, and during its actual enforcement, the kenel of each assembly, quantity and ratio can be a kind of random change, and its assembly layout type State is likely to increasingly complex.

As shown in figure 3, the digital to analog converter of present embodiment at least includes:

First order resistance string structure 1, it at least includes the multiple first order resistance being connected in series and multiple switch s, and first Level resistance and switch gap arrangement.The resistance all same of multiple first order resistance, is r_main.

Decoder 2, is connected with first order resistance string structure 1, and for the high position control based on supplied with digital signal, output is many Individual control signal, to control the opening and closing of each switch in first order resistance string structure 1.

First univoltage selector 3, is connected with first order resistance string structure 1, for the high position based on supplied with digital signal Control, select first order output voltage from first order resistance string structure 1.

Second univoltage selector 4, is connected with first order resistance string structure 1, for the high position based on supplied with digital signal Control, select the second level output voltage adjacent with first order output voltage from first order resistance string structure.

Second level resistance string structure 5, is connected with the first univoltage selector 3, the second univoltage selector 4, it is extremely respectively Include the multiple second level resistance being connected in series less, for accurately being divided first order output voltage and second level output voltage Pressure.The resistance all same of multiple second level resistance, is r_minor.

3rd univoltage selector 6, is connected with second level resistance string structure 5, for the low level based on supplied with digital signal Control, select output voltage from second level resistance string structure 5, as the output analog voltage of digital to analog converter.

Wherein, supplied with digital signal is n position, is expressed as b_n-1～b₀, the low level of supplied with digital signal is m position, is expressed as b_m-1～b₀, a high position for supplied with digital signal is n-m position, is expressed as b_n-1～b_m.The digital to analog converter of present embodiment has two-stage Circuit.First order circuit is mainly by first order resistance string structure 1, decoder 2, the first univoltage selector 3 and the second univoltage Selector 4 is constituted, and first order circuit is by height (n-m) the position signal of supplied with digital signal, i.e. b_n-1～b_mControl that is to say, that Decoder 2, the first univoltage selector 3 and the second univoltage selector 4 all by supplied with digital signal height (n-m) position signal, I.e. b_n-1～b_mControl.Second level circuit is mainly made up of second level resistance string structure 5 and the 3rd univoltage selector 6, and second Level circuit is by the low m position signal of supplied with digital signal, i.e. b_m-1～b₀Control that is to say, that the 3rd univoltage selector 6 is by defeated Enter low m position signal, the i.e. b of digital signal_m-1～b₀Control.

In addition, in the present embodiment, the first univoltage selector 3 can be tree-like switch arrays, fully decoded switch arrays Any type of univoltage selecting switch arrays such as row, two-dimension addressing switch arrays or three-dimensional search switch array.Likewise, Second voltage selector 4 can be tree-like switch arrays, fully decoded switch arrays, two-dimension addressing switch arrays or three-dimensional addressing Any type of univoltage selecting switch array such as switch arrays.Decoder 2 can for tree-like switch arrays decoder, two dimension or Any type of decoder circuits such as person's three-dimensional search switch array decoder.

Therefore, the digital to analog converter of present embodiment, by increase in first order resistance string structure a series of switch with And control the decoder of these switches so that second level resistance string structure and first order resistance string structure form the relation of series connection, The electric current allowing first order resistance string structure flows through second level resistance string structure, thus avoiding positioned at traditional digital to analog converter two The offset error that unity gain buffer between level resistance string causes, reduces area and power consumption, greatly reduces error.

Refer to Fig. 3～Fig. 7, second embodiment of the invention is related to a kind of digital to analog converter, present embodiment and this Bright first embodiment is roughly the same, is in place of difference:

As shown in figure 3, in the present embodiment, first order resistance and switch are 2^n-mIndividual, second level resistance is 2^mIt is individual, And meet equation below:

$r_{\min or}=\frac{r_{main}}{2^m};$

Wherein, r_mainFor the resistance of first order resistance, r_minorFor the resistance of second level resistance, n is the natural number more than 1, m It is the natural number less than n, 2^n-mIndividual switch is expressed as s_0～s_2^n-m-1.

In addition, decoder 2 has 2^n-mIndividual control signal outfan, for output 2^n-mIndividual control signal, the 2 of decoder 2^{n -m}Individual control signal outfan and 2^n-mIndividual switch s_0～s_2^n-m- 1 connects one to one.

In addition, as shown in figure 4, the 2 of decoder 2 output^n-mIndividual control signal controls theIndividual switch s_Open, remaining switch cuts out；Wherein, b_i+mThe i-th+m position signal for supplied with digital signal.

In addition, in first order resistance string structure 1, one end of the 1st switch s_0 connects high reference level v_refh, another The 1st first order resistance of end connection, the 2nd^n-mOne end of individual first order resistance connects the 2nd^n-mIndividual switch s_2^n-m- 1, the other end is even Meet low datum v_refl, remaining first order resistance and remaining switch are connected in series in the way of spaced one by one.

In addition, the first univoltage selector 3 and the second univoltage selector 4 are respectively provided with 2^n-mIndividual datum input and One datum outfan, the 2 of the first univoltage selector 3^n-mIndividual datum input connects one to one 2^n-mIndividual Switch s_0～s_2^n-m- 1 high-pressure side, the 2 of the second univoltage selector 4^n-mIndividual datum input connects one to one 2^n-mThe low-pressure end of individual first order resistance, the datum outfan of the first univoltage selector 3 is used for exporting first order output electricity Pressure, the datum outfan of the second univoltage selector 4 is used for exporting second level output voltage, the electricity of first order output voltage Pressure value is more than the magnitude of voltage of second level output voltage, and meets equation below:

$v_h=\frac{v_{refh}-v_{refl}}{2^{n-m}}(1+\underset{i=0}{\overset{n-m-1}{\σ}}{2}^i{b}_{i+m})+v_{refl},$

$v_l=\frac{v_{refh}-v_{refl}}{2^{n-m}}\underset{i=0}{\overset{n-m-1}{\σ}}{2}^i{b}_{i+m}+v_{refl};$

Wherein, v_hFor the magnitude of voltage of first order output voltage, v_lFor the magnitude of voltage of second level output voltage, v_refhFor senior staff officer Examine level, v_reflFor low datum, b_i+mThe i-th+m position signal for supplied with digital signal.

Specifically, taking the structure of first order circuit in Fig. 3 as a example, first order resistance string structure 1 is by 2^n-mIndividual resistance is r_mainFirst order resistance and 2^n-mIndividual switch s_0～s_2^n-m- 1 is composed in series, and switch s_0 one end connects high reference level v_refh, The other end connects the upper end of the first order resistance being located at top in first order resistance string structure 1, first order resistance string structure 1 middle position Connect low datum v in the lower end of the first order resistance of bottom_refl, upper end connecting valve s_2^n-m- 1 lower end, rest switch It is sequentially inserted between adjacent first order resistance.Decoder 2 is by height (n-m) position of supplied with digital signal, i.e. b_n-1-b_mControl, Output 2^n-mIndividual control signal controlling switch s_0～s_2^n-m- 1 opening and closing.First univoltage selector 3 and second single electricity Pressure selector 4 is all by height (n-m) position of supplied with digital signal, i.e. b_n-1-b_mControl, select from first order resistance string structure 1 respectively Select two neighboring voltage, i.e. first order output voltage and second level output voltage, magnitude of voltage is respectively v_hAnd v_l, and v_h＞ v_l.The One univoltage selector 3 and the second univoltage selector 4 all comprise 2^n-mIndividual datum input, is wherein output as v_h? The datum input of one univoltage selector 3 is connected to switch s_0～s_2 in turn^n-m- 1 upper end, is output as v_l? It is r that the datum input of two univoltage selectores 4 is connected to resistance in turn_mainFirst order resistance lower end.The first order The v of output in circuit_h、v_lUse for second level circuit.

In addition, in second level resistance string structure 5,2^mIndividual second level resistance is sequentially connected in series；Wherein, the 1st second Level resistance is also connected with first order output voltage, and the 2nd^mIndividual second level resistance is also connected with second level output voltage.

And, the 3rd univoltage selector 6 has 2^mIndividual datum input and a datum outfan, the 3rd The 2 of univoltage selector^mIndividual datum input connects one to one 2^mThe low-pressure end of individual second level resistance, the 3rd single electricity The datum outfan of pressure selector 6 is used for exporting the output analog voltage of digital to analog converter, and meets equation below:

$v_{out}=\frac{v_h-v_l}{2^m}\underset{i=0}{\overset{m-1}{\σ}}{2}^i{b}_i+v_l=\frac{v_{refh}-v_{refl}}{2^n}\underset{i=0}{\overset{n-1}{\σ}}{2}^i{b}_i+v_{refl};$

Wherein, v_outFor the output analog voltage of digital to analog converter, v_hFor the magnitude of voltage of first order output voltage, v_lFor second The magnitude of voltage of level output voltage, v_refhFor high reference level, v_reflFor low datum, b_iI-th bit letter for supplied with digital signal Number.

Specifically, taking the structure of second level circuit in Fig. 3 as a example, second level resistance string structure 5 is by 2^mIndividual resistance is r_minorSecond level resistant series composition, andIt is located at the second level electricity on top in second level resistance string structure 5 The upper end of resistance and the voltage v of first order circuit output_hConnect, in second level resistance string structure 5, be located at the second level resistance of bottom Lower end and first order circuit output voltage v_lConnect.3rd univoltage selector 6 is subject to the low m position, i.e. of supplied with digital signal b_m-1-b₀Control, the 3rd univoltage selector 6 comprises 2^mIndividual datum input, is sequentially connected to second level resistance string knot In structure 5, each resistance is r_minorSecond level resistance bottom, output be expressed as v_out, i.e. the final output mould of D/A converting circuit Intend voltage.

The operation principle of the digital to analog converter of present embodiment is as follows:

Digital to analog converter receives n position supplied with digital signal, and decoder 2 is subject to height (n-m) position, i.e. of supplied with digital signal b_n-1-b_mControl, the 2 of output^n-mIndividual control signal, controls the switch s_0～s_2 in first order resistance string structure 1^n-m- 1 opens Or close, and it is directed to every group of supplied with digital signal, switch s_0～s_2^n-mIn -1, only one of which switch is in open mode, remaining Switch is closed, as shown in figure 4, the switch in first order resistance string structure 1Open, its Remaining switch closure.Now, the voltage v of first order circuit output_hAnd v_lTop and bottom with second level resistance string structure 2 respectively It is connected, therefore second level resistance string structure 5 is inserted in first order resistance string structure 1, second level resistance string structure 5 and first Level resistance string structure 1 forms the relation of series connection, and current direction as shown by arrows, and then can obtain this digital to analog converter second level The output voltage of the 3rd univoltage selector 6 in circuit, as shown in figure 4, v_outIt is the simulation electricity corresponding to supplied with digital signal Pressure value, this completes the function of digital-to-analogue conversion.

As an example, the 10-bit digital to analog converter based on present embodiment is emulated.It is illustrated in figure 5 this The simulation result of the transmission curve of 10-bit digital to analog converter, wherein v_refhAnd v_reflIt is respectively 5v and 0v；As Fig. 6 and Fig. 7 respectively Integral nonlinearity for this 10-bit digital to analog converter and the simulation curve of differential nonlinearity.These simulation results are verified further The effectiveness of present embodiment.

Therefore, the digital to analog converter of present embodiment, second level resistance string structure and first order resistance string structure are with defeated Enter digital signal is not in different series connection together it is allowed to the electric current of first order resistance string structure flows through second level resistance string Structure, improves conversion accuracy, reduces area and power consumption, greatly reduces error.

It is seen that, present embodiment is further improved embodiment on the basis of first embodiment, the first enforcement The relevant technical details mentioned in mode are still effective in the present embodiment, in order to reduce repetition, repeat no more here.Accordingly Ground, the relevant technical details mentioned in present embodiment are also applicable in first embodiment.

In sum, the digital to analog converter of the present invention, has the advantages that present configuration is simple, low in energy consumption, face Long-pending little, and there is high accuracy.Specifically, compared with traditional two-stage resistance string dac of prior art, the tradition two of prior art Level resistance string dac needs to increase by two unity gain buffers between two-stage resistance string, thus eliminating second level resistance string Load effect to first order resistance string, on the one hand this increase power consumption and area, and on the other hand above all unit gain is delayed The offset voltage rushing device can introduce error for digital to analog converter；And the present invention only need to increase by one in first order resistance string structure is Row switch and control the decoder of these switches so that second level resistance string structure and first order resistance string structure are with input Digital signal be not in different series connection together it is allowed to the electric current of first order resistance string structure flows through second level resistance string knot Structure, thus eliminating the unity gain buffer between two-stage resistance string, reducing area and power consumption, greatly reducing error. In addition, compared with another kind of resistance string dac of prior art, another kind of resistance string dac of prior art needs in second level electricity Increase by two current-mirror structure current sources being made up of mos pipe in resistance string, because mos pipe has channel-length modulation, because The size of this two current sources can be affected by first order resistance string output voltage, causes this two-stage resistance string dac final Output analog voltage is also affected, so that the precision of this two-stage resistance string dac reduces；And the invention enables the second level is electric Resistance string structure can form with first order resistance string structure and be connected in series it is allowed to the electric current of first order resistance string structure flows through second Level resistance string structure, thus eliminate in the resistance string of the second level two current sources of increase, it is to avoid final output simulation electricity Pressure is affected it is ensured that the high accuracy of digital to analog converter.So, the present invention effectively overcomes various shortcoming of the prior art And have high industrial utilization.

Above-mentioned the embodiment only principle of the illustrative present invention and its effect, not for the restriction present invention.Any Those skilled in the art all can be modified to above-mentioned embodiment or changed without prejudice under the spirit and the scope of the present invention Become.Therefore, such as those of ordinary skill in the art without departing from disclosed spirit and technological thought Lower all completed equivalent modifications or change, must be covered by the claim of the present invention.

Claims (10)

1. a kind of digital to analog converter, for being converted to analogue signal it is characterised in that described digital-to-analogue turns by the digital signal of input Parallel operation at least includes:

First order resistance string structure, it at least includes the multiple first order resistance being connected in series and multiple switch, the described first order Resistance and the arrangement of described switch gap；

Decoder, is connected with described first order resistance string structure, for the high position control based on described supplied with digital signal, output Multiple control signal, to control the opening and closing of each switch in described first order resistance string structure；

First univoltage selector, is connected with described first order resistance string structure, for the height based on described supplied with digital signal Position controls, and selects first order output voltage from described first order resistance string structure；

Second univoltage selector, is connected with described first order resistance string structure, for the height based on described supplied with digital signal Position controls, and selects the second level output voltage adjacent with described first order output voltage from described first order resistance string structure；

Second level resistance string structure, is connected with described first univoltage selector, described second univoltage selector, it is extremely respectively Include the multiple second level resistance being connected in series less, for entering described first order output voltage and described second level output voltage The accurate partial pressure of row；

3rd univoltage selector, is connected with described second level resistance string structure, for low based on described supplied with digital signal Position controls, and selects output voltage, as the output analog voltage of described digital to analog converter from the resistance string structure of the described second level.

2. digital to analog converter according to claim 1 it is characterised in that described supplied with digital signal be n position, described input The low level of digital signal is m position, and a high position for described supplied with digital signal is n-m position, and described first order resistance and described switch are equal For 2^n-mIndividual, described second level resistance is 2^mIndividual, and meet equation below:

$r_{minor}=\frac{r_{main}}{2^m};$

Wherein, r_mainFor the resistance of described first order resistance, r_minorFor the resistance of described second level resistance, n is the nature more than 1 Number, m is the natural number less than n.

3. digital to analog converter according to claim 2 is it is characterised in that described decoder has 2^n-mIndividual control signal is defeated Go out end, for output 2^n-mIndividual described control signal, the 2 of described decoder^n-mIndividual control signal outfan and 2^n-mIndividual described switch Connect one to one.

4. digital to analog converter according to claim 3 it is characterised in that described decoder output 2^n-mIndividual described control Signal controls theIndividual described switch is opened, and remaining described switch cuts out；Wherein, b_i+mFor described input numeral I-th+m position signal of signal.

5. digital to analog converter according to claim 2 is it is characterised in that in described first order resistance string structure, the 1st One end of described switch connects high reference level, and the other end connects the 1st described first order resistance, and the 2nd^n-mThe individual described first order One end of resistance connects the 2nd^n-mIndividual described switch, the other end connect low datum, remaining described first order resistance and remaining Described switch be connected in series in the way of spaced one by one.

6. digital to analog converter according to claim 5 is it is characterised in that described first univoltage selector and described second Univoltage selector is respectively provided with 2^n-mIndividual datum input and a datum outfan, described first univoltage selects The 2 of device^n-mIndividual datum input connects one to one 2^n-mThe high-pressure side of individual described switch, described second univoltage selects The 2 of device^n-mIndividual datum input connects one to one 2^n-mThe low-pressure end of individual described first order resistance, described first single electricity The datum outfan of pressure selector is used for exporting described first order output voltage, the reference of described second univoltage selector Level output end is used for exporting described second level output voltage, and the magnitude of voltage of described first order output voltage is more than the described second level The magnitude of voltage of output voltage, and meet equation below:

$v_h=\frac{v_{refh}-v_{refl}}{2^{n-m}}(1+\underset{i=0}{\overset{n-m-1}{\mathrm{\σ}}}{2}^i{b}_{i+m})+v_{refl},$

$v_l=\frac{v_{refh}-v_{refl}}{2^{n-m}}\underset{i=0}{\overset{n-m-1}{\mathrm{\σ}}}{2}^i{b}_{i+m}+v_{refl};$

Wherein, v_hFor the magnitude of voltage of described first order output voltage, v_lFor the magnitude of voltage of described second level output voltage, v_refhFor Described high reference level, v_reflFor described low datum, b_i+mThe i-th+m position signal for described supplied with digital signal.

7. digital to analog converter according to claim 6 is it is characterised in that in the resistance string structure of the described second level, and 2^mIndividual institute State second level resistance to be sequentially connected in series；Wherein, the 1st described second level resistance is also connected with described first order output voltage, the 2^mIndividual described second level resistance is also connected with described second level output voltage.

8. digital to analog converter according to claim 7 is it is characterised in that described 3rd univoltage selector has 2^mIndividual ginseng Examine level input and a datum outfan, the 2 of described 3rd univoltage selector^mIndividual datum input is one by one Correspondence is connected to 2^mThe low-pressure end of individual described second level resistance, the datum outfan of described 3rd univoltage selector is used for Export the output analog voltage of described digital to analog converter, and meet equation below:

$v_{out}=\frac{v_h-v_l}{2^m}\underset{i=0}{\overset{m-1}{\mathrm{\σ}}}{2}^i{b}_i+v_l=\frac{v_{refh}-v_{refl}}{2^n}\underset{i=0}{\overset{n-1}{\mathrm{\σ}}}{2}^i{b}_i+v_{refl};$

Wherein, vout is the output analog voltage of described digital to analog converter, v_hFor the magnitude of voltage of described first order output voltage, v_l For the magnitude of voltage of described second level output voltage, v_refhFor described high reference level, v_reflFor described low datum, b_iFor institute State the i-th bit signal of supplied with digital signal.

9. the digital to analog converter according to any one of claim 1～8 it is characterised in that described first univoltage selector, Described second univoltage selector and described 3rd univoltage selector are tree-like, fully decoded, two-dimension addressing or three-dimensional and seek The univoltage selecting switch array of location form.

10. the digital to analog converter according to any one of claim 1～8 it is characterised in that described decoder be tree-like, two Dimension addressing or the switch arrays decoder of three-dimensional addressing form.