CN103166645B - A kind of R-2R type d convertor circuit - Google Patents
A kind of R-2R type d convertor circuit Download PDFInfo
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- CN103166645B CN103166645B CN201110418177.XA CN201110418177A CN103166645B CN 103166645 B CN103166645 B CN 103166645B CN 201110418177 A CN201110418177 A CN 201110418177A CN 103166645 B CN103166645 B CN 103166645B
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Abstract
The invention discloses a kind of R-2R type d convertor circuit, include the control logic of series connection, R-2R type digital to analog converter and switch, also there is at output the electric capacity of a ground connection.In 4 of the arbitrary neighborhood of the binary digital signal of n position, comprise at least one position and change 1 into from 0, also comprise at least one position and change 0 into from 1; And the described position occurring to change has every except low four except being arranged in the binary digital signal of described n position at least, the condition disconnected for making switch.When control logic finds that the condition making switch disconnect meets, first the control signal of output switch makes switch disconnect, then the binary digital signal on one, 2n-4 road after conversion is exported to R-2R type digital to analog converter, after the digital-to-analogue conversion time of this R-2R type digital to analog converter arrives, then the control signal of output switch makes switch close.The present invention thoroughly avoids the overshoot phenomenon of output, guarantees the stable of the control system using this R-2R d convertor circuit.
Description
Technical field
The present invention relates to a kind of digital to analog converter (DAC, Digital-AnalogConverter) circuit.
Background technology
Divide according to internal circuit configuration, DAC can be divided into weighting resistor type, trapezoidal R-2R network-type, inverted ladder type R-2R network-type etc.These are known by persons skilled in the art, such as, " modem electronic circuitry " book (author: Wang Zhigang; Publishing house of Tsing-Hua University 2003 publishes) Section 8.1 just have a detailed description.The DAC of R-2R type wherein because structure is simple, area is little, precision is suitable, speed and power consumption compromise, be widely used in semiconductor integrated circuit.
Refer to Fig. 1, this is the schematic diagram of the R-2R type DAC of 8.Resistance wherein only has R and 2R two kinds, D0, D1 ..., D7n, D7p for input data, OUT is output voltage.Comprise 8 parallel branches in circuit, each route resistance 2R and two switches Si (i is the natural number between 1 ~ 16) forms, and this branch road is connected reference voltage VDD and ground GND by these two switches respectively.There is resistance R isolated between each branch road.
In theory, each branch road of R-2R type DAC only needs a switch, and this switch alternatively by this branch road or connection reference voltage VDD, or connects ground GND.But when realizing R-2R type DAC in semiconductor integrated circuit, if find that each branch road only has a switch, then the one or more situations that may produce this switch and need to connect reference voltage VDD and ground GND simultaneously of n position digital signal.Therefore be two switches by each local road design.
Refer to Fig. 2, this is a kind of existing R-2R type DAC-circuit.It includes switch drive (SwitchDriver) 11 and the DAC12 of series connection.Described DAC12 is exactly the physical circuit of the R-2R type DAC shown in Fig. 1.Described switch drive 11 is used for the binary digital signal DI<N-1:0> of a n position, road to be converted to the binary digital signal in one, 2n-4 road, makes it adapt to the input of DAC12.
Refer to Fig. 3, the concrete conversion method of switch drive 11 pairs of signals is: it is the binary digital signal in one, a road that low four DI<0>, DI<1>, DI<2>, DI<3> of the binary digital signal DI<N-1:0> of described n position export respectively, the 5th and more high-order, and each is divided into two-way binary digital signal.Partition mode illustrates with two examples.
Example 1: the five DI<4> is signal " 0 ", represents with trailing edge.5th DI<4> is divided into DN<4> and DP<4>, as long as the trailing edge of DP<4> is later than the trailing edge 1 ~ 5ns (nanosecond) of DN<4>.
Example 2: the six DI<5> are signal " 1 ", represent with rising edge.6th DI<5> is divided into DN<5> and DP<5>, as long as the rising edge of DP<5> is early than the rising edge 1 ~ 5ns of DN<5>.
When formally inputing to DAC12, the binary digital signal in one, four tunnel exported by low four DI<0>, DI<1>, DI<2>, DI<3> of the binary digital signal DI<N-1:0> of n position, there is a signal copied on each road, and so just constitutes the binary digital signal in one, 2n road.
R-2R type DAC-circuit shown in Fig. 2 may run into the phenomenon of the signal of telecommunication overshoot of output.Such as, 8 binary digital signal DI<7:0>, when being converted to 80h from 7Fh (h at end represents it is hexadecimal), are namely equivalent to be converted to 10000000b from 01111111b (b at end represents it is binary system).For R-2R pattern number converter 12, only require that 8 binary digital signal entirety (t in Fig. 3) in official hour are converted to the signal of telecommunication of simulation by it.So likely highest order DI<7> can first change by this R-2R pattern number converter 12, and all the other every DI<6:0> are changed after a while, the analog electrical signal that what this R-2R pattern number converter 12 exported instantaneously in this time difference is corresponding to digital signal 11111111b and FFh, has been flushed to reference voltage VDD on as out (1) signal in Fig. 4.Similarly, this R-2R pattern number converter 12 analog electrical signal that also possibility moment output stage is low, has been flushed to ground GND under as the out (2) in Fig. 4.127 × LSB in Fig. 4,128 × LSB represent the analog electrical signal corresponding to the digital signal of 7Fh and 80h respectively.
The overshoot phenomenon of this R-2R type DAC-circuit easily causes the stability problem of control system, makes its application in the controls really receive challenge and difficulty.
Summary of the invention
Technical problem to be solved by this invention is to provide a kind of new R-2R type DAC-circuit, and it can avoid producing overshoot phenomenon, guarantees that control system is stablized.
For solving the problems of the technologies described above, R-2R type d convertor circuit of the present invention includes the control logic of series connection, R-2R type digital to analog converter and switch, also has the electric capacity of a ground connection at output;
The binary digital signal of one n position, road is converted to the binary digital signal on one, 2n-4 road by described control logic on the one hand, generates the control signal of switch on the other hand;
In 4 of the arbitrary neighborhood of the binary digital signal of n position, comprise at least one position and change into " 1 " from " 0 ", also comprise at least one position and change into " 0 " from " 1 "; And the described position occurring to change has every except low four except being arranged in the binary digital signal of described n position at least, the condition disconnected for making switch;
When control logic finds that the condition making switch disconnect meets, first the control signal of output switch makes switch disconnect, then the binary digital signal on one, 2n-4 road after conversion is exported to R-2R type digital to analog converter, after the digital-to-analogue conversion time of this R-2R type digital to analog converter arrives, then the control signal of output switch makes switch close.
R-2R type d convertor circuit of the present invention, by arranging a switch after R-2R type digital to analog converter, and judge that switch disconnects condition by control logic, thoroughly avoid the overshoot phenomenon of output, guarantee the stable of the control system using this R-2R d convertor circuit.
Accompanying drawing explanation
Fig. 1 is the electrical block diagram of R-2R type digital to analog converter;
Fig. 2 is a kind of structural representation of existing R-2R type d convertor circuit;
Fig. 3 is the schematic diagram that switch driving circuit 11 in Fig. 2 carries out signal conversion;
Fig. 4 is the schematic diagram that existing R-2R type d convertor circuit produces overshoot phenomenon;
Fig. 5 is the structural representation of R-2R type d convertor circuit of the present invention;
Fig. 6 is the schematic diagram that control logic 21 in Fig. 5 carries out signal conversion and output.
Description of reference numerals in figure:
11 is switch driving circuit; 12 is R-2R type digital to analog converter; 21 is control logic; 23 is switch; 24 is electric capacity.
Embodiment
Refer to Fig. 5, R-2R type DAC-circuit of the present invention includes the control logic (ControlLogic) 21 of series connection, DAC12 and switch 23, also has the electric capacity 24 of a ground connection at output OUT.
Described control logic 21 adds an output signal cp and produces logic on the basis of existing switching over 11.
Described DAC12 is exactly the physical circuit form of the R-2R type DAC shown in Fig. 1.
Described switch 23 is controlled the control of the output signal cp of logic 21 and closes or disconnect.
Specifically, the control logic 21 1 aspect Jiang Yilu n binary digital signal DI<N-1:0> in position is converted to the binary digital signal in one, 2n-4 road, make it adapt to the input of DAC12, n can be 8,9,10,11 or 12; Generate the control signal cp of switch 23 on the other hand.
Wherein, the concrete conversion method of control logic 21 pairs of signals is identical with switching over 11, that is: low four DI<0> of the described binary digital signal DI<N-1:0> in n position, DI<1>, DI<2>, it is the digital signal on one, a road that DI<3> exports respectively, 5th and more high-order DI<m> (m is the natural number of >=4) are then divided into two-way binary digital signal DP<m> and DN<m>.When DI<m> represents with trailing edge, as long as the trailing edge that two signals of its partition meet DP<m> is later than the trailing edge 1 ~ 5ns of DN<m>.When DI<m> represents with rising edge, as long as two signals of its partition meet the rising edge 1 ~ 5ns of rising edge early than DN<m> of DP<m>.
Wherein, the logic that control logic 21 generates the control signal cp of switch 23 is: in 4 of the arbitrary neighborhood of the binary digital signal DI<N-1:0> of n position, comprise at least one position to change into " 1 " from " 0 ", also comprise at least one position and change into " 0 " from " 1 "; And the described position occurring to change has an every DI<N-1:4> except low four being arranged in the binary digital signal DI<N-1:0> of described n position at least, this is the condition that switch 23 is disconnected.
Refer to Fig. 6, when supposing that signal cp is high level, control switch 23 closes, for control switch during low level 23 disconnects.Further, when control logic 21 finds that the condition making switch 23 disconnect meets, first outputing signal cp makes switch 23 disconnect, and then exports DP<N-1:4>, DN<N-1:4>, D<3:0> to R-2R type digital to analog converter 12.The time that this R-2R type digital to analog converter 12 carries out digital-to-analogue conversion is known, 2 ~ 10ns after this time, and control logic outputs signal cp again makes switch 23 close.
Preferably, the output resistance of the conducting resistance <0.1*R-2R type digital to analog converter 12 of described switch 23, such switch 23 would not impact the conversion speed of R-2R type digital to analog converter 12.
Described electric capacity 24 maintains output OUT and still has output when switch 23 disconnects, play filter action when switch 23 closes.Its preferable range is 0.1 ~ 50pF.
After adopting R-2R type d convertor circuit of the present invention, completely eliminate the hidden danger that overshoot phenomenon appears in output, as shown in out (3) signal in Fig. 4.
These are only the preferred embodiments of the present invention, be not intended to limit the present invention.For a person skilled in the art, the present invention can have various modifications and variations.Within the spirit and principles in the present invention all, any amendment done, equivalent replacement, improvement etc., all should be included within protection scope of the present invention.
Claims (5)
1. a R-2R type d convertor circuit, is characterized in that, includes the control logic of sequential series, R-2R type digital to analog converter and switch, also has the electric capacity of a ground connection at output;
The binary digital signal of one n position, road is converted to the binary digital signal on one, 2n-4 road by described control logic on the one hand, generates the control signal of switch on the other hand; The rule that the binary digital signal of one n position, road is converted to the binary digital signal on one, 2n-4 road is by described control logic: to export respectively be the digital signal on one, a road to low four of the binary digital signal in described n position, and the 5th and more high-order DI<m> are then divided into two-way binary digital signal DP<m> and DN<m>;
When DI<m> represents with trailing edge, the trailing edge that its two signals broken meet DP<m> is later than the trailing edge 1 ~ 5ns of DN<m>;
When DI<m> represents with rising edge, two signals of its partition meet the rising edge 1 ~ 5ns of rising edge early than DN<m> of DP<m>;
In 4 of the arbitrary neighborhood of the binary digital signal of n position, comprise at least one position and change into " 1 " from " 0 ", also comprise at least one position and change into " 0 " from " 1 "; And the described position occurring to change has every except low four except being arranged in the binary digital signal of described n position at least, the condition disconnected for making switch;
When control logic finds that the condition making switch disconnect meets, first the control signal of output switch makes switch disconnect, then the binary digital signal on one, 2n-4 road after conversion is exported to R-2R type digital to analog converter, after the digital-to-analogue conversion time of this R-2R type digital to analog converter arrives, then the control signal of output switch makes switch close.
2. R-2R type d convertor circuit according to claim 1, is characterized in that, the value of n is the natural number in 8 ~ 12.
3. R-2R type d convertor circuit according to claim 1, is characterized in that, described control logic, after the digital-to-analogue conversion time of R-2R type digital to analog converter arrives, waits for 2 ~ 10ns, then the control signal of output switch makes switch close.
4. R-2R type d convertor circuit according to claim 1, is characterized in that, the output resistance of the R-2R type digital to analog converter of the conducting resistance < 1/10th times of described switch.
5. R-2R type d convertor circuit according to claim 1, it is characterized in that, the capacitance of described electric capacity is between 0.1 ~ 50pF.
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| CN201110418177.XA CN103166645B (en) | 2011-12-14 | 2011-12-14 | A kind of R-2R type d convertor circuit |
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Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5008676A (en) * | 1990-02-15 | 1991-04-16 | Mitsubishi Denki Kabushiki Kaisha | Digital/analog converter |
| US6975261B1 (en) * | 2004-07-28 | 2005-12-13 | Intersil America's Inc. | High accuracy digital to analog converter using parallel P and N type resistor ladders |
| CN101136635A (en) * | 2007-09-04 | 2008-03-05 | 中国电子科技集团公司第二十四研究所 | Method for reducing inverse R-2R structure D/A converter output current overshoot |
| CN102130688A (en) * | 2010-01-20 | 2011-07-20 | 上海华虹Nec电子有限公司 | Resistance network type digital to analog converter structure |
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Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5008676A (en) * | 1990-02-15 | 1991-04-16 | Mitsubishi Denki Kabushiki Kaisha | Digital/analog converter |
| US6975261B1 (en) * | 2004-07-28 | 2005-12-13 | Intersil America's Inc. | High accuracy digital to analog converter using parallel P and N type resistor ladders |
| CN101136635A (en) * | 2007-09-04 | 2008-03-05 | 中国电子科技集团公司第二十四研究所 | Method for reducing inverse R-2R structure D/A converter output current overshoot |
| CN102130688A (en) * | 2010-01-20 | 2011-07-20 | 上海华虹Nec电子有限公司 | Resistance network type digital to analog converter structure |
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Owner name: SHANGHAI HUAHONG GRACE SEMICONDUCTOR MANUFACTURING Free format text: FORMER OWNER: HUAHONG NEC ELECTRONICS CO LTD, SHANGHAI Effective date: 20140107 |
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