CN112636755A - Current source of digital-to-analog converter, calibration device, calibration system and calibration method - Google Patents
Current source of digital-to-analog converter, calibration device, calibration system and calibration method Download PDFInfo
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Abstract
The invention discloses a current source, a calibration device, a calibration system and a calibration method of a digital-to-analog converter, wherein the current source of a current steering digital-to-analog converter comprises an LSB unit current source, a calibration current source, a first current output end and a second current output end; the thermometer code calibration current source array comprises a plurality of thermometer code calibration current sources, and each thermometer code calibration current source receives a thermometer code control signal and outputs a thermometer code calibration current according to the thermometer code control signal so as to compensate the output current of the thermometer code current sources; the binary code calibration current source array comprises a plurality of binary code calibration current sources, and each binary code calibration current source receives one path of binary code control signal and outputs a binary code calibration current according to the binary code control signal so as to compensate the output current of the binary code current source. The invention realizes the calibration of the current sources with equal weights and the calibration of the current sources with other weights.
Description
Technical Field
The present invention relates to the field of electronic technologies, and in particular, to a current source, a calibration device, a calibration system, and a calibration method for a digital-to-analog converter.
Background
A high-speed high-precision DAC (digital-to-analog converter) usually adopts a current steering structure, and each current source in a current source array is controlled by input data through a switch to output a current corresponding to the input data, and then converted into a voltage signal at an output end. Since the high-precision DAC generally has a large number of bits, the number of current sources in the corresponding current source array is also large. Gradient errors, secondary errors, random errors and the like are inevitably introduced in the manufacturing process of the integrated circuit due to some non-ideal factors, mismatching among current sources is caused, INL (integral nonlinearity) and DNL (differential nonlinearity) of the DAC are influenced, and harmonic waves or burrs are generated in the output frequency spectrum of the DAC. Therefore, in order to reduce INL/DNL caused by current source mismatch and improve the linearity of the DAC, a calibration circuit is required to calibrate the matching degree between the main current sources of the DAC.
A traditional DAC calibration needs a reference current source, and the calibration circuit can only calibrate current sources with the same weight as the reference current source in the DAC, but cannot calibrate current sources with other weights. Because current sources with other weights cannot be calibrated, in order to improve the accuracy of the DAC, the current source area of each binary code current source unit in the DAC needs to be increased, so that the parasitic capacitance is large, and the dynamic performance of the circuit is poor.
Disclosure of Invention
The invention provides a current source, a calibration device, a calibration system and a calibration method of a digital-to-analog converter, aiming at overcoming the defect that only a current source with the weight equal to that of a reference current source in a DAC can be calibrated and current sources with other weights cannot be calibrated in the prior art.
The invention solves the technical problems through the following technical scheme:
the invention provides a current source of a current-steering digital-to-analog converter with calibration, wherein the current source of the current-steering digital-to-analog converter comprises a thermometer code current source array and a binary code current source array; the thermometer code current source array comprises a plurality of thermometer code current sources which are connected in parallel, and the weights corresponding to the thermometer code current sources are the same; the binary code current source array comprises a plurality of binary code current source units which are connected in parallel, the weight corresponding to each binary code current source is gradually reduced or increased, and the current steering digital-to-analog converter current source further comprises an LSB unit current source, a calibration current source, a first current output end and a second current output end; the calibration current source comprises a thermometer code calibration current source array and a binary code calibration current source array;
each thermometer code current source is also connected with the first current output end through a first thermometer code switch, connected with the second current output end through a second thermometer code switch and grounded or connected with a load through a third thermometer code switch; each binary code current source is also connected with the first current output end through a first binary code switch, connected with the second current output end through a second binary code switch and grounded or connected with a load through a third binary code switch;
the LSB unit current source is connected with the first current output end through a first LSB unit current source switch, connected with the second current output end through a second LSB unit current source switch and grounded or connected with a load through a third LSB unit current source switch;
the first thermometer code switch, the second thermometer code switch, the third thermometer code switch, the first binary code switch, the second binary code switch, the third binary code switch, the first LSB unit current source switch, the second LSB unit current source switch, and the third LSB unit current source switch are turned on or off according to a switch control signal;
the thermometer code calibration current source array comprises a plurality of thermometer code calibration current sources, each thermometer code calibration current source is correspondingly connected with one thermometer code current source, and each thermometer code calibration current source receives one path of thermometer code control signal and outputs a thermometer code calibration current according to the thermometer code control signal so as to compensate the output current of the thermometer code current sources;
the binary code calibration current source array comprises a plurality of binary code calibration current sources, each binary code calibration current source is correspondingly connected with one binary code current source, and each binary code calibration current source receives one path of binary code control signal and outputs a binary code calibration current according to the binary code control signal so as to compensate the output current of the binary code current source.
Preferably, the thermometer code calibration current source array and the binary code calibration current source array are implemented using pmos and/or nmos.
Preferably, when said thermometer code current source array and said binary code current source array are implemented in pmos and said thermometer code calibration current source array and said binary code calibration current source array are implemented in pmos, said thermometer code calibration current source array performs additive compensation on said thermometer code current source array and said binary code calibration current source array performs additive compensation on said binary code current source array;
or, when said thermometer code current source array and said binary code current source array are implemented with pmos and said thermometer code calibration current source array and said binary code calibration current source array are implemented with nmos, said thermometer code calibration current source array performs subtraction compensation on said thermometer code current source array, and said binary code calibration current source array performs subtraction compensation on said binary code current source array;
or, when said thermometer code current source array and said binary code current source array are implemented with pmos and said thermometer code calibration current source array and said binary code calibration current source array are implemented with pmos and nmos, said thermometer code calibration current source array performs add and subtract compensation to said thermometer code current source array, said binary code calibration current source array performs add and subtract compensation to said binary code current source array;
or, when said thermometer code current source array and said binary code current source array are implemented using nmos, and when said thermometer code calibration current source array and said binary code calibration current source array are implemented using pmos, said thermometer code calibration current source array performs subtraction compensation on said thermometer code current source array, and said binary code calibration current source array performs subtraction compensation on said binary code current source array;
or, when said thermometer code current source array and said binary code current source array are implemented using nmos, and when said thermometer code calibration current source array and said binary code calibration current source array are implemented using nmos, said thermometer code calibration current source array performs additive compensation on said thermometer code current source array, and said binary code calibration current source array performs additive compensation on said binary code current source array;
or, when said thermometer code current source array and said binary code current source array are implemented with nmos and when said thermometer code calibration current source array and said binary code calibration current source array are implemented with pmos and nmos, said thermometer code calibration current source array performs subtraction and addition compensation on said thermometer code current source array, and said binary code calibration current source array performs subtraction and addition compensation on said binary code current source array.
The invention also provides a calibration device of the current source of the current steering digital-to-analog converter, which comprises a calibration control logic and a comparison circuit;
a first input end and a second input end of the comparison circuit are respectively connected with a first current output end and a second current output end of the current source with the calibration current steering digital-to-analog converter, and an output end of the comparison circuit is connected with an input end of the calibration control logic;
the comparison circuit is used for comparing the current values of the first current source end and the second current end and outputting the comparison result to the calibration control logic;
the calibration control logic is configured to output a switch control signal to the first thermometer code switch, the second thermometer code switch, the third thermometer code switch, the first binary code switch, the second binary code switch, the third binary code switch, the first LSB unit current source switch, the second LSB unit current source switch, and the third LSB unit current source switch, and output a thermometer code control signal to a thermometer code calibration current source array and a binary code control signal to a binary code calibration current source array according to a comparison result.
Preferably, the comparison circuit comprises a voltage comparator, a first load resistor and a second load resistor;
when the thermometer code current source array and the binary code current source array are implemented by adopting pmos, one end of the first load resistor is electrically connected with the first current output end and the first input end of the voltage comparator respectively, and the other end of the first load resistor is grounded; one end of the second load resistor is electrically connected with the second current output end and the second input end of the voltage comparator respectively, the other end of the second load resistor is grounded, and the output end of the voltage comparator is electrically connected with the input end of the calibration control logic;
or, when the thermometer code current source array and the binary code current source array are implemented by nmos, one end of the first load resistor is electrically connected with the first current output end and the first input end of the voltage comparator respectively, and the other end of the first load resistor is connected with a power supply; one end of the second load resistor is electrically connected with the second current output end and the second input end of the voltage comparator respectively, the other end of the second load resistor is connected with the power supply, and the output end of the voltage comparator is electrically connected with the input end of the calibration control logic.
Preferably, the comparison circuit comprises a current comparator;
and a first input end and a second input end of the current comparator are respectively and electrically connected with the first current output end and the second current output end, and an output end of the current comparator is electrically connected with an input end of the calibration control logic.
Preferably, the calibration device further comprises a storage unit;
the memory cell is electrically connected with the calibration control logic;
the storage unit is used for storing thermometer code control signals and binary code control signals output by the calibration control logic.
The invention also provides a current source with a calibrated and stored current-steering digital-to-analog converter, which comprises the current source with the calibrated current-steering digital-to-analog converter and a storage unit;
the storage unit is electrically connected with the current steering digital-to-analog converter with calibration;
the memory cell is used for storing a thermometer code control signal and a binary code control signal, outputting the thermometer code control signal to the thermometer code calibration current source, and outputting the binary code control signal to the binary code calibration current source.
The invention also provides a calibration system of the current source of the current-steering digital-to-analog converter with calibration, which comprises the current source of the current-steering digital-to-analog converter with calibration and the calibration device of the current source of the current-steering digital-to-analog converter.
The invention also provides a calibration method of the current source of the current steering digital-to-analog converter with calibration, which comprises the following steps:
taking a thermometer code current source of the thermometer code current source array or a binary code current source in the binary code current source array as a calibration object;
according to a switch control signal output by the calibration control logic, a first calibration switch connected with the calibration object is conducted, a second calibration switch connected with a current source with lower weight than the calibration object is conducted, and a grounding switch or a load switch connected with other current sources with weight equal to or higher than that of the calibration object is conducted;
adjusting a thermometer code control signal and a binary code control signal output by the calibration control logic by adopting a successive approximation method so that the first current output end is equal to the second current output end;
when the first calibration switch is a switch electrically connected with the output end of the first current source, the corresponding second calibration switch is a switch electrically connected with the output end of the second current source;
when the first calibration switch is a switch electrically connected to the second current source output terminal, the corresponding second calibration switch is a switch electrically connected to the first current source output terminal.
The positive progress effects of the invention are as follows: the invention provides a current source, a calibration device, a calibration system and a calibration method of a digital-to-analog converter, which are characterized in that an LSB unit current source, a thermometer code calibration current source array, a binary code calibration current source array and switches corresponding to the current sources are arranged, each thermometer code calibration current source is correspondingly connected with one thermometer code current source, each binary code calibration current source is correspondingly connected with one binary code current source, each binary code calibration current source receives one path of binary code control signal and outputs a binary code calibration current according to the binary code control signal so as to compensate the output current of the binary code current source, thereby realizing the calibration of the current sources with equal weight and the calibration of the current sources with other weights, further reducing the area of the binary code current sources, the parasitic capacitance becomes smaller, and the dynamic performance of the circuit is improved.
Drawings
Fig. 1 is a schematic block diagram of a current source with a calibrated current-steering dac in embodiment 1 of the present invention;
fig. 2 is a schematic structural diagram of a first current source with a calibrated current-steering dac in embodiment 1 of the present invention;
fig. 3 is a schematic structural diagram of a second current source with a calibrated current-steering dac in embodiment 1 of the present invention;
fig. 4 is a schematic structural diagram of a third current source with a calibrated current-steering dac in embodiment 1 of the present invention;
fig. 5 is a schematic structural diagram of a fourth current source with a calibrated current-steering dac in embodiment 1 of the present invention;
fig. 6 is a schematic structural diagram of a calibration apparatus for a current source of a current-steering dac in embodiment 2 of the present invention;
fig. 7 is a schematic structural diagram of a calibration apparatus for a current source of a current-steering dac in embodiment 2 of the present invention;
fig. 8 is a schematic structural diagram of a calibration apparatus for a current source of a third current-steering dac in embodiment 2 of the present invention;
fig. 9 is a flowchart of a calibration method for a current source with a calibrated current-steering dac according to embodiment 3 of the present invention.
Detailed Description
The invention is further illustrated by the following examples, which are not intended to limit the scope of the invention.
Example 1
As shown in fig. 1, the present embodiment discloses a current-steering dac current source 1 with calibration, which includes a thermometer code current source array 11, a binary code current source array 12; the thermometer code current source array 11 comprises a plurality of thermometer code current sources which are connected in parallel, the weight corresponding to each thermometer code current source is the same, the binary code current source array 12 comprises a plurality of binary code current source units which are connected in parallel, the weight corresponding to each binary code current source is gradually reduced or increased, and the current steering digital-to-analog converter current source further comprises an LSB unit current source 13, a calibration current source 14, a first current output end and a second current output end; the calibration current source 14 includes a thermometer code calibration current source array 141 and a binary code calibration current source array 142;
each thermometer code current source is also connected with a first current output end through a first thermometer code switch, connected with a second current output end through a second thermometer code switch and grounded or connected with a load through a third thermometer code switch; each binary code current source is also connected with the first current output end through the first binary code switch, connected with the second current output end through the second binary code switch and grounded or connected with a load through the third binary code switch;
the LSB unit current source 13 is connected with the first current output end through the first LSB unit current source switch, connected with the second current output end through the second LSB unit current source switch and grounded or connected with a load through the third LSB unit current source switch;
the first thermometer code switch, the second thermometer code switch, the third thermometer code switch, the first binary code switch, the second binary code switch, the third binary code switch, the first LSB unit current source switch, the second LSB unit current source switch and the third LSB unit current source switch are switched on or switched off according to the switch control signal;
the thermometer code calibration current source array 141 comprises a plurality of thermometer code calibration current sources, each thermometer code calibration current source is correspondingly connected with one thermometer code current source, and each thermometer code calibration current source receives one path of thermometer code control signal and outputs a thermometer code calibration current according to the thermometer code control signal so as to compensate the output current of the thermometer code current sources;
the binary code calibration current source array 142 includes a plurality of binary code calibration current sources, each of which is correspondingly connected to one of the binary code current sources, and each of which receives one of the binary code control signals and outputs a binary code calibration current according to the binary code control signal, so as to compensate the output current of the binary code current source.
Specifically, the LSB unit current source is represented by B0_ dmy, and its output current magnitude is ideally IB0. The thermometer code current source array 11 comprises 2M-1 weights all of size 2LM and L are positive integers. In FIGS. 2 to 5, 2M1 high M-bit thermometer code current sources T1, T2 … T (2)M-1) and the ideal values of the output current are IM＝2L·IB0And each thermometer code current source is coded with a Thermo-code. The binary code current source array 12 comprises L binary code current sources with binary weights, each of which has a current weight of 2L-1、2L-2…22、21、20Each binary code current source is respectively represented by B (L-1), B (L-2), …, B2, B1 and B0, and the output current of each binary code current source is 2L-1·IB0，2L-2·IB0，…，22·IB0，2·IB0，IB0And each Binary-coded current source is coded with a Binary-code. Where the sum of M, L equals N, which is the resolution of the entire DAC. Some high-precision DACs are divided into three sections, the middle bits are coded by thermometer codes, the principle is the same, and two sections of codes are taken as an example here. The thermometer code calibration current source array 141 includes 2M-1 temperatureThe current source is calibrated by a meter code, which is respectively T1cal、T2cal…T(2M-1)calAnd each thermometer code calibration current source and thermometer code current source T1, T2 … T (2)M-1) one-to-one correspondence, T1calFor calibrating T1, T2calFor calibrating T2, …, T (2)M-1)calFor calibrating T (2)M-1), the current summing point is before the output of the respective current source unit switch, and a cascode transistor can be added after the current summing point. The output current of each calibration current source is adjustable, and a digital code DTx is input by m bitscalControl (x is 0 to 2)M-1). The binary calibration current source array 142 includes L binary calibration current sources, each of which is represented by B (L-1)cal，B(L-2)cal，…，B2cal，B1cal，B0calEach binary-code calibrated current source is represented by a one-to-one correspondence of binary-code current sources B (L-1), B (L-2), …, B2, B1, B0, B (L-1)calFor calibrating B (L-1), B (L-2)calFor calibrating B (L-2), …, B1calFor calibrating B1, B0calFor calibrating B0. The output current of each calibration current source is adjustable, and the digital code DBx is input by n bitscalControlling (x is 0-L-1). Furthermore, each thermometer code current source is connected with a first current output end I through a first thermometer code switchOUTPA second current output terminal I connected to the second thermometer code switchOUTNAnd each binary code current source is connected with the first current output end I through the first binary code switchOUTPA second current output terminal I is connected through a second binary code switchOUTNAnd the LSB unit current source is connected with the first current output end I through the first LSB unit current source switchOUTPA second current output terminal I connected with the second LSB unit current source switchOUTNAnd grounding through a third LSB unit current source switch, wherein the first thermometer code switch, the first binary code switch and the first LSB unit current source switch are marked as SPA second thermometer code switch, a second binary code switch, and a second LSB sheetThe bit current source switch is marked as SnThe third thermometer code switch, the third binary code switch and the third LSB unit current source switch are marked as S0. Switch SpAnd SnFor the switches used during normal operation of the DAC, the current in the respective current source unit is controlled via IOUTPOr IOUTNAnd (4) outflow, wherein only one of the valves can be closed at the same time. S0Switches which are used only during calibration (S is also used during calibration)pAnd Sn) For passing current to non-IOUTPIs not IOUTNHere, the current may be made to flow to a dummy load or the like, as an example.
In an implementable manner, the thermometer code calibration current source array 11 and the binary code calibration current source array 12 may be implemented using pmos and/or nmos. The following are specific examples of several possible specific circuit configurations that may be implemented:
the first circuit configuration: as shown in fig. 2, when the thermometer code current source array 11 and the binary code current source array 12 are implemented by pmos and the thermometer code calibration current source array 141 and the binary code calibration current source array 142 are implemented by pmos, the thermometer code current source and the corresponding thermometer code calibration current source are connected in parallel and the current directions of the two current sources are the same, so as to implement the addition compensation of the thermometer code current source by the thermometer code calibration current source, and the binary code current source and the corresponding binary code calibration current source are connected in parallel and the current directions of the two current sources are the same, so as to implement the addition compensation of the binary code calibration current source by the binary code calibration current source.
The second circuit structure: as shown in fig. 3, when the thermometer code current source array 11 and the binary code current source array 12 are implemented by pmos and the thermometer code calibration current source array 141 and the binary code calibration current source array 142 are implemented by nmos, the thermometer code current source and the corresponding thermometer code calibration current source are connected in parallel and the current directions of the two current sources are opposite, so as to implement the subtraction compensation of the thermometer code current source by the thermometer code calibration current source, and the binary code current source and the corresponding binary code calibration current source are connected in parallel and the current directions of the two current sources are opposite, so as to implement the subtraction compensation of the binary code current source by the binary code calibration current source.
The third circuit structure: as shown in fig. 4, when the thermometer code current source array 11 and the binary code current source array 12 are implemented by pmos and the thermometer code calibration current source array 141 and the binary code calibration current source array 142 are implemented by pmos and nmos, it is equivalent to a thermometer code current source calibrated by two thermometer code calibration current sources (a thermometer code calibration current source implemented by pmos (hereinafter referred to as P-type thermometer code calibration current source) and a thermometer code calibration current source implemented by nmos (hereinafter referred to as N-type thermometer code calibration current source)), one binary code current source calibrated by two binary code calibration current sources (a binary code calibration current source implemented by pmos (hereinafter referred to as P-type binary code calibration current source) and a binary code calibration current source implemented by nmos (hereinafter referred to as N-type binary code calibration current source)), the thermometer code current source is connected with the corresponding P-type thermometer code calibration current source and the corresponding N-type thermometer code calibration current source in parallel, the current directions of the thermometer code current source and the corresponding P-type thermometer code calibration current source are the same, and the current directions of the thermometer code current source and the corresponding N-type thermometer code calibration current source are opposite, so that the addition compensation of the P-type thermometer code calibration current source to the thermometer code current source and the subtraction compensation of the N-type thermometer code calibration current source to the thermometer code current source are realized, the binary code current source is connected with the corresponding P-type binary code calibration current source and the corresponding N-type binary code calibration current source in parallel, the current directions of the binary code current source and the corresponding P-type binary code calibration current source are the same, and the current directions of the corresponding N-type binary code calibration current source are opposite, so that the addition compensation of the P-type binary code calibration current source to the binary code current source and the phase compensation of the N-type binary code And (5) subtracting and compensating.
The fourth circuit configuration: as shown in fig. 5, when the thermometer code current source array 11 and the binary code current source array 12 are implemented by nmos and the thermometer code calibration current source array 141 and the binary code calibration current source array 142 are implemented by nmos, the thermometer code current source and the corresponding thermometer code calibration current source are connected in parallel and the current directions of the two current sources are the same, so as to implement the additive compensation of the thermometer code current source by the thermometer code calibration current source, and the binary code current source and the corresponding binary code calibration current source are connected in parallel and the current directions of the two current sources are the same, so as to implement the additive compensation of the binary code calibration current source by the binary code calibration current source.
Fifth circuit configuration: when the thermometer code current source array 11 and the binary code current source array 12 are implemented by nmos and the thermometer code calibration current source array 141 and the binary code calibration current source array 142 are implemented by pmos, the thermometer code current source and the corresponding thermometer code calibration current source are connected in parallel, and the current directions of the two current sources are opposite, so that the subtraction compensation of the thermometer code current source by the thermometer code calibration current source is realized, the binary code current source and the corresponding binary code calibration current source are connected in parallel, and the current directions of the two current sources are opposite, so that the subtraction compensation of the binary code current source by the binary code calibration current source is realized.
A sixth circuit configuration: when the thermometer code current source array 11 and the binary code current source array 12 are implemented by nmos and the thermometer code calibration current source array 141 and the binary code calibration current source array 142 are implemented by pmos and nmos, it is equivalent to one thermometer code current source calibrated by two thermometer code calibration current sources (one thermometer code calibration current source implemented by pmos (hereinafter referred to as P-type thermometer code calibration current source) and one thermometer code calibration current source implemented by nmos (hereinafter referred to as N-type thermometer code calibration current source)), one binary code current source calibrated by two binary code calibration current sources (one binary code calibration current source implemented by pmos (hereinafter referred to as P-type binary code calibration current source) and one binary code calibration current source implemented by nmos (hereinafter referred to as N-type binary code calibration current source)), the thermometer code current source is connected with the corresponding P-type thermometer code calibration current source and the corresponding N-type thermometer code calibration current source in parallel, the current directions of the thermometer code current source and the corresponding P-type thermometer code calibration current source are opposite, and the current directions of the thermometer code current source and the corresponding N-type thermometer code calibration current source are the same, so that the subtraction compensation of the P-type thermometer code calibration current source to the thermometer code current source and the addition compensation of the N-type thermometer code calibration current source to the thermometer code current source are realized, the binary code current source is connected with the corresponding P-type binary code calibration current source and the corresponding N-type binary code calibration current source in parallel, the current directions of the binary code current source and the corresponding P-type binary code calibration current source are opposite, the current directions of the N-type binary code calibration current source are the same, so that the subtraction compensation of the P-type binary code calibration current source to the binary code current source and the phase compensation of the N-type binary code calibration current And (5) adding compensation.
The current source of the current steering dac with calibration of this embodiment is implemented by setting the LSB unit current source and the thermometer code calibration current source array, the binary code calibration current source array and the switches corresponding to the current sources, where each thermometer code calibration current source is correspondingly connected to one thermometer code current source, each binary code calibration current source is correspondingly connected to one binary code current source, each binary code calibration current source receives one binary code control signal and outputs a binary code calibration current according to the binary code control signal to compensate the output current of the binary code current source, thereby realizing that not only the current sources with equal weight can be calibrated, but also the current sources with other weights can be calibrated, therefore, the area of the binary code current source is reduced, the parasitic capacitance is reduced, and the dynamic performance of the circuit is improved.
Example 2
As shown in fig. 6 to 8, the present embodiment discloses a calibration apparatus for a current source of a current steering dac, which includes a calibration control logic 2 and a comparison circuit;
the first input end and the second input end of the comparison circuit are respectively connected with the first current output end I of the current source 1 of the current-steering digital-to-analog converter with calibrationOUTPAnd a second current output terminal IOUTNThe output end of the comparison circuit is connected with the input end of the calibration control logic 2; the comparison circuit is used for comparing the first current output end IOUTPAnd a second current output terminal IOUTNAnd outputs the comparison resultTo calibration control logic 2; the calibration control logic 2 is used for outputting a switch control signal Sx (x is p,0, n) to the first thermometer code switch, the second thermometer code switch, the third thermometer code switch, the first binary code switch, the second binary code switch, the third binary code switch, the first LSB unit current source switch, the second LSB unit current source switch and the third LSB unit current source switch, and outputting a thermometer code control signal DTx according to the comparison resultcal(x is 0 to 2)M-1) to thermometer code current source array 11, binary code control signal DBxcal(x is 0-L-1) to the binary code calibration current source array 12. Thermometer code control signal DTxcal(x is 0 to 2)M-1) an output for controlling a thermometer code calibration current source; binary code control signal DBxcal(x is 0-L-1) for controlling the output of the binary code calibration current source; s of each current source unitp、Sn、S0For controlling the current source output to IOUTPOr IOUTNOr ground.
The comparison circuit may be implemented using a voltage comparator or a current comparator. When the current source implementation modes of the current-steering digital-to-analog converter are different, the implementation modes of the comparison circuit are also different, specifically as follows:
in a first circuit configuration, as shown in fig. 6, when the current source 1 of the current steering dac is implemented by pmos, the comparison circuit includes a voltage comparator 3 and a first load resistor RL1And a second load resistor RL2While, the first load resistance RL1One end of the first current output terminal I is connected with the first current output terminal IOUTPThe positive input end of the voltage comparator 3 is electrically connected, and the other end of the voltage comparator is grounded; a second load resistor RL2One end of the first current output terminal is respectively connected with the second current output terminal IOUTNThe output end of the voltage comparator 3 is electrically connected with the input end of the calibration control logic 2, and the comparison result D is output to the calibration control logic 2out。
In a second circuit configuration, as shown in fig. 7, when the current source 1 of the current-steering dac is implemented by nmos, the comparison circuit includes a voltage comparator 3 and a first load resistor RL1And a firstTwo load resistors RL2First load resistance RL1One end of the first current output terminal I is connected with the first current output terminal IOUTPThe positive input end of the voltage comparator 3 is electrically connected, and the other end of the voltage comparator is connected with a power supply; a second load resistor RL2One end of the first current output terminal is respectively connected with the second current output terminal IOUTNThe output end of the voltage comparator 3 is electrically connected with the input end of the calibration control logic 2, and the comparison result D is output to the calibration control logic 2out。
In the third circuit structure, as shown in fig. 8, when the current source 1 of the current-steering dac is implemented by pmos, the comparison circuit includes a current comparator 5, and a positive input terminal and a negative input terminal of the current comparator 5 are respectively connected to the first current output terminal IOUTPAnd a second current output terminal IOUTNThe output terminal of the current comparator 5 is electrically connected with the input terminal of the calibration control logic, and the comparison result D is output to the calibration control logic 2out。
In the fourth circuit structure, when the current source 1 of the current-steering dac is implemented by nmos, the comparison circuit includes a current comparator, and the circuit connection is the same as that in the third case, which is not described herein again.
In an alternative embodiment, the calibration device further comprises a memory unit 4; the storage unit 4 is electrically connected with the calibration control logic 2; the storage unit 4 is used for storing thermometer code control signals and binary code control signals output by the calibration control logic. After the calibration is finished, the calibration result (DB 0)cal～DB(L-1)calAnd DT0cal～DT(2M-1)calValue(s) is written into the memory unit 4 for later retrieval.
The calibrating device of this embodiment compares the electric current of current rudder digital-to-analog converter current source through being equipped with the comparator to control the output of calibration control logic, thereby can not only calibrate the current source that the weight equals, but also can calibrate the current source of other weights, and then make binary code current source area reduce, parasitic capacitance diminishes, has improved the dynamic behavior of circuit. In addition, the implementation mode of the calibration device is different along with different implementation modes of the current source of the current steering digital-to-analog converter, and further the calibration of various current steering digital-to-analog converter current sources is realized through various modes.
Example 3
The embodiment discloses a current source of a current-steering digital-to-analog converter with calibration and storage, wherein the current source of the current-steering digital-to-analog converter with calibration and storage comprises the current source of the current-steering digital-to-analog converter with calibration and a storage unit; the storage unit is electrically connected with the current steering digital-to-analog converter with calibration; the storage unit is used for storing a thermometer code control signal and a binary code control signal, outputting the thermometer code control signal to the thermometer code calibration current source and outputting the binary code control signal to the binary code calibration current source.
In this embodiment, the current source of the current steering dac is provided with a storage unit, so that the thermometer code control signal and the binary code control signal can be stored, and the thermometer code control signal and the binary code control signal can be respectively output to the thermometer code calibration current source and the binary code calibration current source when the current steering dac is used.
Example 4
The embodiment discloses a calibration system of a current source of a current-steering digital-to-analog converter with calibration, which comprises the current source of the current-steering digital-to-analog converter with calibration and a calibration device of the current source of the current-steering digital-to-analog converter.
The calibration system of this embodiment is through setting up LSB unit current source and thermometer code calibration current source array, the switch that binary code calibration current source array and current source correspond, every thermometer code calibration current source corresponds a thermometer code current source of connection respectively, every binary code calibration current source corresponds a binary code current source of connection respectively, every binary code calibration current source receives binary code control signal of the same way and exports binary code calibration current according to binary code control signal respectively, compensate with the output current to the binary code current source, thereby realized not only can calibrate the current source that the weight equals, but also can calibrate the current source of other weights, and then make binary code current source area reduce, parasitic capacitance diminishes, the dynamic behavior of circuit has been improved.
Example 5
As shown in fig. 9, the present embodiment discloses a calibration method for a current source of a current-steering dac with calibration, where the calibration method includes:
step S101, taking a thermometer code current source of the thermometer code current source array or a binary code current source in the binary code current source array as a calibration object;
step S102, a first calibration switch connected with a calibration object is conducted according to a switch control signal output by the calibration control logic, a second calibration switch connected with a current source with lower weight than the calibration object is conducted, and a grounding or load switch connected with other current sources with weight equal to or higher than that of the calibration object is conducted; for example, if the calibration object is a binary code current source, a ground or load switch connected to another binary code current source with a higher weight than the binary code current source and a thermometer code current source needs to be turned on; if the calibration object is a thermometer code current source, grounding or load switches with weights equal to other thermometer code current sources of the thermometer code current source are required to be conducted;
and step S103, adjusting the thermometer code control signal and the binary code control signal output by the calibration control logic by adopting a successive approximation method so as to enable the first current output end to be equal to the second current output end.
When the first calibration switch is a switch electrically connected with the output end of the first current source, the corresponding second calibration switch is a switch electrically connected with the output end of the second current source;
when the first calibration switch is a switch electrically connected to the second current source output terminal, the corresponding second calibration switch is a switch electrically connected to the first current source output terminal.
The grounding or load connecting switch is a third thermometer code switch, a third binary code switch or a third LSB unit current source switch.
In the present embodiment, taking fig. 2 as an example, if the lowest bit current source B0 is calibrated, the objective of the calibration is to adjust IB0calTo make its current source and corresponding calibrationThe sum of the output currents of the quasi-current sources is equal to the output current of B0-dmy, i.e. IB0+IB0cal＝IB0_dmy；
For cell B1, the calibration target is IB1+IB1cal＝IB0+IB0cal+IB0_dmy；
For cell B2, the calibration target is IB2+IB2cal＝IB1+IB1cal+IB0+IB0cal+IB0_dmy；
……
It can be seen that to calibrate the high order bits, the low order bits must be calibrated first, and thus the calibration sequence is from low order bits to high order bits. The current source cells of the lowest few bits may not need calibration, and in this case the corresponding calibration current sources are not needed. Assuming that the lowest order current source cell requiring calibration is B4, the calibration sequence is B4 → B5 → … → B (L-1) → T0 → T1 → … → T (2)M-1)。
Calibration procedure assuming that all bits need calibration: calibrating B0 first, the calibration control logic controls S of B0_ dmypClosed to make its current pass through the first current output terminal IOUTPOutputting; calibration logic controls S of B0nClosed to make its current pass through second current output terminal IOUTNOutputting; the calibration logic controls S of other current source units0Closed, making its current flow to ground. Calibrating the control logic output DB0 using successive approximationcalTo 100 … 000, the output D of the comparator is checkedoutIf high, DB0calThe most significant bit remains 1, otherwise it is 0. DB0 is thencalSecond highest position 1, inspection DoutIf high, DB0calThe next highest bit remains 1, otherwise it is 0. Repeat the above process until DB0calAll bits are asserted.
Calibration B1 is then initiated, and the calibration control logic controls S of B0_ dmy and B0pClose, control S of B1nClose, control othersS of the current source0And (5) closing. Then determining DB1 from high order to low order by successive approximationcal。
The same method was used to calibrate B2, B3, … B (L-1) in turn and determine DB2cal、DB3cal、…DB(L-1)calThe value of (c).
Calibration T0 is then initiated, and the calibration control logic controls S of B0_ dmy, B0, B1, … B (L-1)pClose, control S of T0nClosed, controlling S of other current sources0And (5) closing. Then, the DT0 is determined from high order to low order by successive approximationcal。
The same method is adopted to calibrate T1, T2 and … T (2)M-1), determine DT2cal、DT3cal、…DT(2M-1)calThe value of (c).
The calibration method for current source of current steering dac with calibration disclosed in this embodiment utilizes the relationship that a certain high bit of a binary weighted current source is equal to the sum of all low bits plus one Least Significant Bit (LSB), omits a reference current source, can calibrate a current source with arbitrary weight, by turning on a first calibration switch connected to the calibration object, turning on a second calibration switch connected to a current source with weight lower than that of the calibration object, turning on a ground or load switch connected to another current source with weight higher than that of the calibration object, and adjusting a thermometer code control signal and a binary code control signal output by the calibration control logic by successive approximation, so that the first current output end is equal to the second current output end, thereby achieving not only calibration for current sources with equal weight, but also calibration for current sources with other weights, therefore, the area of the binary code current source is reduced, the parasitic capacitance is reduced, and the dynamic performance of the circuit is improved.
While specific embodiments of the invention have been described above, it will be appreciated by those skilled in the art that this is by way of example only, and that the scope of the invention is defined by the appended claims. Various changes and modifications to these embodiments may be made by those skilled in the art without departing from the spirit and scope of the invention, and these changes and modifications are within the scope of the invention.
Claims (10)
1. A current source of a current-steering digital-to-analog converter with calibration comprises a thermometer code current source array and a binary code current source array; the thermometer code current source array comprises a plurality of thermometer code current sources which are connected in parallel, and the weights corresponding to the thermometer code current sources are the same; the binary code current source array comprises a plurality of binary code current source units which are connected in parallel, and the weight corresponding to each binary code current source is gradually reduced or increased, and the binary code current source array is characterized in that the current steering digital-to-analog converter current source further comprises an LSB unit current source, a calibration current source, a first current output end and a second current output end; the calibration current source comprises a thermometer code calibration current source array and a binary code calibration current source array;
each thermometer code current source is also connected with the first current output end through a first thermometer code switch, connected with the second current output end through a second thermometer code switch and grounded or connected with a load through a third thermometer code switch; each binary code current source is also connected with the first current output end through a first binary code switch, connected with the second current output end through a second binary code switch and grounded or connected with a load through a third binary code switch;
the LSB unit current source is connected with the first current output end through a first LSB unit current source switch, connected with the second current output end through a second LSB unit current source switch and grounded or connected with a load through a third LSB unit current source switch;
the first thermometer code switch, the second thermometer code switch, the third thermometer code switch, the first binary code switch, the second binary code switch, the third binary code switch, the first LSB unit current source switch, the second LSB unit current source switch, and the third LSB unit current source switch are turned on or off according to a switch control signal;
the thermometer code calibration current source array comprises a plurality of thermometer code calibration current sources, each thermometer code calibration current source is correspondingly connected with one thermometer code current source, and each thermometer code calibration current source receives one path of thermometer code control signal and outputs a thermometer code calibration current according to the thermometer code control signal so as to compensate the output current of the thermometer code current sources;
the binary code calibration current source array comprises a plurality of binary code calibration current sources, each binary code calibration current source is correspondingly connected with one binary code current source, and each binary code calibration current source receives one path of binary code control signal and outputs a binary code calibration current according to the binary code control signal so as to compensate the output current of the binary code current source.
2. The current-steering dac current source with calibration of claim 1 wherein the thermometer-code calibration current source array and the binary-code calibration current source array are implemented with pmos and/or nmos.
3. The calibrated current-steering dac current source of claim 2 wherein when said thermometer-code current source array and said binary-code current source array are implemented in pmos and when said thermometer-code calibration current source array and said binary-code calibration current source array are implemented in pmos, said thermometer-code calibration current source array additively compensates said thermometer-code current source array and said binary-code calibration current source array additively compensates said binary-code current source array;
or, when said thermometer code current source array and said binary code current source array are implemented with pmos and when said thermometer code calibration current source array and said binary code calibration current source array are implemented with nmos, said thermometer code calibration current source array performs subtraction compensation on said thermometer code current source array and said binary code calibration current source array performs subtraction compensation on said binary code current source array;
or, when said thermometer code current source array and said binary code current source array are implemented with pmos and when said thermometer code calibration current source array and said binary code calibration current source array are implemented with pmos and nmos, said thermometer code calibration current source array performs add and subtract compensation to said thermometer code current source array and said binary code calibration current source array performs add and subtract compensation to said binary code current source array;
or, when said thermometer code current source array and said binary code current source array are implemented using nmos, and when said thermometer code calibration current source array and said binary code calibration current source array are implemented using pmos, said thermometer code calibration current source array performs subtraction compensation on said thermometer code current source array, and said binary code calibration current source array performs subtraction compensation on said binary code current source array;
or, when said thermometer code current source array and said binary code current source array are implemented using nmos, and when said thermometer code calibration current source array and said binary code calibration current source array are implemented using nmos, said thermometer code calibration current source array performs additive compensation on said thermometer code current source array, and said binary code calibration current source array performs additive compensation on said binary code current source array;
or, when said thermometer code current source array and said binary code current source array are implemented with nmos and when said thermometer code calibration current source array and said binary code calibration current source array are implemented with pmos and nmos, said thermometer code calibration current source array performs subtraction and addition compensation on said thermometer code current source array, and said binary code calibration current source array performs subtraction and addition compensation on said binary code current source array.
4. A calibration device for a current source of a current steering digital-to-analog converter is characterized by comprising calibration control logic and a comparison circuit;
a first input and a second input of the comparison circuit are connected to a first current output and a second current output, respectively, of a current source with a calibrated current-steering digital-to-analog converter according to any of claims 1 to 3, an output of the comparison circuit is connected to an input of the calibration control logic;
the comparison circuit is used for comparing the current values of the first current source end and the second current end and outputting the comparison result to the calibration control logic;
the calibration control logic is configured to output a switch control signal to the first thermometer code switch, the second thermometer code switch, the third thermometer code switch, the first binary code switch, the second binary code switch, the third binary code switch, the first LSB unit current source switch, the second LSB unit current source switch, and the third LSB unit current source switch, and output a thermometer code control signal to a thermometer code calibration current source array and a binary code control signal to a binary code calibration current source array according to a comparison result.
5. The calibration device for a current source of a current steering digital-to-analog converter of claim 4, wherein the comparison circuit comprises a voltage comparator, a first load resistance, and a second load resistance;
when the thermometer code current source array and the binary code current source array are implemented by adopting pmos, one end of the first load resistor is electrically connected with the first current output end and the first input end of the voltage comparator respectively, and the other end of the first load resistor is grounded; one end of the second load resistor is electrically connected with the second current output end and the second input end of the voltage comparator respectively, the other end of the second load resistor is grounded, and the output end of the voltage comparator is electrically connected with the input end of the calibration control logic;
or, when the thermometer code current source array and the binary code current source array are implemented by nmos, one end of the first load resistor is electrically connected with the first current output end and the first input end of the voltage comparator respectively, and the other end of the first load resistor is connected with a power supply; one end of the second load resistor is electrically connected with the second current output end and the second input end of the voltage comparator respectively, the other end of the second load resistor is connected with the power supply, and the output end of the voltage comparator is electrically connected with the input end of the calibration control logic.
6. The calibration device for a current source of a current steering digital-to-analog converter of claim 4, wherein the comparison circuit comprises a current comparator;
and a first input end and a second input end of the current comparator are respectively and electrically connected with the first current output end and the second current output end, and an output end of the current comparator is electrically connected with an input end of the calibration control logic.
7. The calibration device for a current source of a current steering digital-to-analog converter of claim 4, wherein the calibration device further comprises a memory unit;
the memory cell is electrically connected with the calibration control logic;
the storage unit is used for storing thermometer code control signals and binary code control signals output by the calibration control logic.
8. A calibrated and stored current-steering dac current source, characterized in that the calibrated and stored current-steering dac current source comprises a calibrated current-steering dac current source and a memory unit according to any of claims 1 to 3;
the storage unit is electrically connected with the current steering digital-to-analog converter with calibration;
the memory cell is used for storing a thermometer code control signal and a binary code control signal, outputting the thermometer code control signal to the thermometer code calibration current source, and outputting the binary code control signal to the binary code calibration current source.
9. Calibration system with calibrated current-steering dac current source, characterized in that the calibration system comprises a calibrated current-steering dac current source according to any of claims 1 to 3, a calibration means of a current-steering dac current source according to any of claims 4 to 7.
10. A method for calibrating a current source of a current-steering digital-to-analog converter with calibration, the method comprising:
using a thermometer code current source of the thermometer code current source array or a binary code current source of the binary code current source array as claimed in claim 8 or claim 9 as a calibration object;
according to a switch control signal output by the calibration control logic, a first calibration switch connected with the calibration object is conducted, a second calibration switch connected with a current source with lower weight than the calibration object is conducted, and a grounding switch or a load switch connected with other current sources with weight equal to or higher than that of the calibration object is conducted;
adjusting a thermometer code control signal and a binary code control signal output by the calibration control logic by adopting a successive approximation method so that the first current output end is equal to the second current output end;
when the first calibration switch is a switch electrically connected with the output end of the first current source, the corresponding second calibration switch is a switch electrically connected with the output end of the second current source;
when the first calibration switch is a switch electrically connected to the second current source output terminal, the corresponding second calibration switch is a switch electrically connected to the first current source output terminal.
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Cited By (2)
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|---|---|---|---|---|
| CN113985759A (en) * | 2021-09-29 | 2022-01-28 | 山东爱通工业机器人科技有限公司 | Data acquisition and conversion module for robot polishing workstation |
| CN116015307A (en) * | 2023-03-27 | 2023-04-25 | 电子科技大学 | Current steering DAC |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113985759A (en) * | 2021-09-29 | 2022-01-28 | 山东爱通工业机器人科技有限公司 | Data acquisition and conversion module for robot polishing workstation |
| CN116015307A (en) * | 2023-03-27 | 2023-04-25 | 电子科技大学 | Current steering DAC |
| CN116015307B (en) * | 2023-03-27 | 2023-05-23 | 电子科技大学 | Current steering DAC |
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