Current source circuit and oscillator

Abstract

The embodiment of the invention provides a current source circuit and an oscillator. The current source circuit comprises a positive temperature coefficient current generating circuit, a negative temperature coefficient current generating circuit and a current summing circuit, the positive temperature coefficient current generating circuit is connected with the negative temperature coefficient current generating circuit and the current summing circuit. The current generator generates positive temperature coefficient current; the negative temperature coefficient current generating circuit is connected with the current summing circuit; the negative-temperature-coefficient current generator generates negative-temperature-coefficient current. The current summing circuit is respectively connected with the positive temperature coefficient current generating circuit and the negative temperature coefficient current generating circuit; and the current mirroring module is used for mirroring the positive temperature coefficient current and the negative temperature coefficient current according to a corresponding preset proportion, summing the mirrored positive temperature coefficient current and the mirrored negative temperature coefficient current, generating a zero temperature coefficient current and outputting the zero temperature coefficient current. The magnitude of the zero temperature coefficient current is not kept constant along with the temperature change, so that the problems that the output current changes obviously along with the temperature and the temperature characteristic is poor are solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of power supply, in particular to a current source circuit and an oscillator. BACKGROUND

[0002] In analog and mixed-signal integrated circuits, oscillators are widely used in clock generation, timing control and data synchronization scenarios. The stability of the output frequency, especially the temperature drift characteristic, directly affects the accuracy and reliability of the system. In order to improve the frequency stability of the oscillator, a reference current source is usually used to provide a bias current for it. However, in the prior art, a traditional reference current source circuit is used as a bias source. Such circuits often do not fully consider the temperature compensation mechanism, resulting in a significant change in output current with temperature and poor temperature characteristics. SUMMARY

[0003] In view of the above problems, the present application is proposed to provide a current source circuit and an oscillator that overcome the above problems or at least partially solve the above problems.

[0004] In order to solve the above problems, the present application discloses a current source circuit, which comprises a positive temperature coefficient current generating circuit, a negative temperature coefficient current generating circuit and a current summing circuit.

[0005] The positive temperature coefficient current generating circuit is connected with the negative temperature coefficient current generating circuit and the current summing circuit respectively; and is used for generating a positive temperature coefficient current.

[0006] The negative temperature coefficient current generating circuit is connected with the current summing circuit; and is used for generating a negative temperature coefficient current.

[0007] The current summing circuit is connected with the positive temperature coefficient current generating circuit and the negative temperature coefficient current generating circuit respectively; and is used for mirroring the positive temperature coefficient current and the negative temperature coefficient current according to a corresponding preset ratio, summing the mirrored positive temperature coefficient current and the mirrored negative temperature coefficient current, and outputting a zero temperature coefficient current.

[0008] Optionally, the positive temperature coefficient current generating circuit comprises a first switch tube, a second switch tube, a third switch tube, a fourth switch tube and a first resistor.

[0009] The input end of the first switch tube is connected with a power supply.

[0010] The input end of the second switch tube is connected with the power supply, and the control end of the second switch tube is connected with the control end of the first switch tube.

[0011] The input end of the third switch tube is connected with the output end of the first switch tube.

[0012] The input end of the fourth switch tube is connected with the control end of the third switch tube and the output end of the second switch tube respectively, the control end of the fourth switch tube is connected with the output end of the second switch tube and the input end of the fourth switch tube respectively, and the output end of the fourth switch tube is connected with the control end of the third switch tube and the ground respectively.

[0013] One end of the first resistor is connected with the output end of the second switch tube and the control end of the fourth switch tube respectively, and the other end of the first resistor is connected with the control end of the third switch tube and the input end of the fourth switch tube respectively.

[0014] Optionally, the first switch tube and the second switch tube are in the saturation region, and the third switch tube and the fourth switch tube are in the sub-threshold region.

[0015] Optionally, the negative temperature coefficient current generating circuit comprises a fifth switch tube, a sixth switch tube, a seventh switch tube, an eighth switch tube, a ninth switch tube and a second resistor.

[0016] The input end of the fifth switch tube is connected with the power supply, and the control end of the fifth switch tube is connected with the control end of the first switch tube and the control end of the second switch tube respectively.

[0017] The input end of the sixth switch tube is connected with the output end of the fifth switch tube, and the output end of the sixth switch tube is grounded.

[0018] The input end of the seventh switch tube is connected with the power supply, and the output end of the seventh switch tube is connected with the control end of the sixth switch tube and the ground respectively.

[0019] The input end of the eighth switch tube is connected with the power supply, and the control end of the eighth switch tube is connected with the control end of the seventh switch tube.

[0020] The input end of the ninth switch tube is connected with the output end of the eighth switch tube, and the control end of the ninth switch tube is connected with the output end of the seventh switch tube and the control end of the sixth switch tube respectively.

[0021] One end of the second resistor is connected with the output end of the sixth switch tube and the ground respectively, and the other end of the second resistor is connected with the control end of the sixth switch tube, the output end of the seventh switch tube and the control end of the ninth switch tube respectively.

[0022] Optionally, the fifth switch tube, the seventh switch tube, the eighth switch tube and the ninth switch tube are in the saturation region, and the sixth switch tube is in the sub-threshold region.

[0023] Optionally, the current summation circuit comprises a first current mirror branch and a second current mirror branch.

[0024] The first current mirror branch is connected with the positive temperature coefficient current generation circuit, and is configured to mirror and output the positive temperature coefficient current according to a corresponding preset ratio.

[0025] The second current mirror branch is connected with the negative temperature coefficient current generation circuit and the first current mirror branch respectively, and is configured to mirror and output the negative temperature coefficient current according to a corresponding preset ratio, so that the mirrored positive temperature coefficient current and the mirrored negative temperature coefficient current are added to generate a zero temperature coefficient current.

[0026] Optionally, the first current mirror branch comprises a tenth switch tube.

[0027] The input end of the tenth switch tube is connected with the power supply, the control end of the tenth switch tube is connected with the control end of the first switch tube and the control end of the second switch tube respectively, and the tenth switch tube is configured to mirror and output the positive temperature coefficient current according to a corresponding preset ratio.

[0028] Optionally, the second current mirror branch comprises an eleventh switch tube.

[0029] The input end of the eleventh switch tube is connected with the power supply, the control end of the eleventh switch tube is connected with the control end of the seventh switch tube and the control end of the eighth switch tube respectively, and the output end of the eleventh switch tube is connected with the output end of the tenth switch tube, and the eleventh switch tube is configured to mirror and output the negative temperature coefficient current according to a corresponding preset ratio.

[0030] Optionally, the tenth switch tube is a plurality of parallel switch tubes, and the eleventh switch tube is a plurality of parallel switch tubes.

[0031] Optionally, the first switch tube, the second switch tube, the third switch tube, the fourth switch tube, the fifth switch tube, the sixth switch tube, the seventh switch tube, the eighth switch tube, the ninth switch tube, the tenth switch tube and the eleventh switch tube are MOS tubes.

[0032] Correspondingly, the embodiment of the present application discloses a kind of oscillators, comprising the current source circuit as any one described above.

[0033] The embodiment of the present application comprises the following advantages:

[0034] The current source circuit of this invention includes a positive temperature coefficient current generating circuit, a negative temperature coefficient current generating circuit, and a current summing circuit. The positive temperature coefficient current generating circuit is connected to both the negative temperature coefficient current generating circuit and the current summing circuit to generate a positive temperature coefficient current. The negative temperature coefficient current generating circuit is connected to the current summing circuit to generate a negative temperature coefficient current. The current summing circuit is connected to both the positive and negative temperature coefficient current generating circuits to mirror the positive and negative temperature coefficient currents according to a preset ratio, and sums the mirrored positive and negative temperature coefficient currents to generate a zero temperature coefficient current for output. This invention uses the current summing circuit to mirror and sum the positive and negative temperature coefficient currents generated by the positive and negative temperature coefficient current generating circuits according to a preset ratio to generate a zero temperature coefficient current. Since the magnitude of the zero temperature coefficient current remains constant regardless of temperature, this avoids the problem of significant temperature variations in the output current and poor temperature characteristics. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of a current source circuit according to an embodiment of the present invention;

[0036] Figure 2 This is a schematic diagram of another current source circuit according to an embodiment of the present invention.

[0037] Figure reference numerals: Positive temperature coefficient current generating circuit 10, first switch 11, second switch 12, third switch 13, fourth switch 14, first resistor 15, negative temperature coefficient current generating circuit 20, fifth switch 21, sixth switch 22, seventh switch 23, eighth switch 24, ninth switch 25, second resistor 26, current summing circuit 30, first current mirror branch 31, tenth switch 311, second current mirror branch 32, eleventh switch 321, power supply 40, inverter chain circuit 50. Detailed Implementation

[0038] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0039] In analog and mixed-signal integrated circuits, oscillators are widely used in clock generation, timing control and data synchronization, etc. The stability of the output frequency, especially the temperature drift characteristic, directly affects the accuracy and reliability of the system. In order to improve the frequency stability of the oscillator, a reference current source is usually used to provide bias current for it. However, in the prior art, a traditional reference current source circuit is used as a bias source, and such a circuit often does not fully consider the temperature compensation mechanism, resulting in a significant change in output current with temperature and poor temperature characteristics.

[0040] In order to suppress the change of frequency with temperature, a reference current source with low temperature coefficient is usually used to provide bias current for the oscillator to achieve temperature compensation of the frequency. The temperature characteristics of bipolar junction transistors (BJT) are used to construct a reference current source, and the reference current generated by the reference current source is used to bias the oscillator, which can effectively reduce the temperature drift of the output frequency. However, bipolar transistors occupy a large area in standard CMOS processes, which is not conducive to high-integration chip design. Secondly, BJT usually needs a large static bias current to work normally, resulting in high power consumption of the reference current source and the overall circuit. In addition, its process compatibility is poor, and it may need additional process steps when integrated into a CMOS flow, increasing manufacturing costs.

[0041] One of the core ideas of the embodiments of the present application is that the positive temperature coefficient current generated by the positive temperature coefficient current generating circuit and the negative temperature coefficient current generated by the negative temperature coefficient current generating circuit are mirrored and summed according to the corresponding preset ratio by the current summing circuit to generate a zero temperature coefficient current. Since the size of the zero temperature coefficient current remains constant with temperature, the problem of significant change in output current with temperature and poor temperature characteristics is avoided.

[0042] Referring to Figure 1 , a structure schematic diagram of a current source circuit according to an embodiment of the present application is shown, which can specifically include the following structure:

[0043] The positive temperature coefficient current generating circuit 10, the negative temperature coefficient current generating circuit 20 and the current summing circuit 30.

[0044] The positive temperature coefficient current generating circuit 10 is connected with the negative temperature coefficient current generating circuit 20 and the current summing circuit 30 respectively; and is used for generating a positive temperature coefficient current.

[0045] The positive temperature coefficient current is also a current proportional to absolute temperature (IPTAT), and the current value of the positive temperature coefficient current increases with the increase of temperature, and has a positive temperature coefficient.

[0046] The negative temperature coefficient current generating circuit 20 is connected with the current summing circuit 30; for generating a negative temperature coefficient current.

[0047] The negative temperature coefficient current is also a current complementary to absolute temperature (ICTAT), the current value of the negative temperature coefficient current decreases with the increase of temperature, and has a negative temperature coefficient.

[0048] The current summing circuit 30 is connected with the positive temperature coefficient current generating circuit 10 and the negative temperature coefficient current generating circuit 20 respectively; for mirroring the positive temperature coefficient current and the negative temperature coefficient current according to the corresponding preset proportion, and summing the mirrored positive temperature coefficient current and the mirrored negative temperature coefficient current to generate and output a zero temperature coefficient current.

[0049] The current summing circuit 30 and the positive temperature coefficient current generating circuit 10 are coupled through a current mirror, the input tube of the current mirror is located in the positive temperature coefficient current generating circuit 10, the output tube is located in the current summing circuit 30, and the current summing circuit 30 mirrors the positive temperature coefficient current generated by the positive temperature coefficient current generating circuit 10 to the summing node inside the current summing circuit 30 according to the corresponding preset proportion through the current mirror structure.

[0050] The current summing circuit 30 and the negative temperature coefficient current generating circuit 20 are coupled through a current mirror, the input tube of the current mirror is located in the negative temperature coefficient current generating circuit 20, the output tube is located in the current summing circuit 30, and the current summing circuit 30 mirrors the negative temperature coefficient current generated by the negative temperature coefficient current generating circuit 20 to the summing node inside the current summing circuit 30 according to the corresponding preset proportion through the current mirror structure.

[0051] The mirrored positive temperature coefficient current and the mirrored negative temperature coefficient current are superimposed at the summing node inside the current summing circuit 30, and a zero temperature coefficient current is generated and output through the complementary offset of the temperature coefficient.

[0052] The current source circuit of the embodiment of the application comprises a positive temperature coefficient current generating circuit, a negative temperature coefficient current generating circuit and a current summing circuit; the positive temperature coefficient current generating circuit is connected with the negative temperature coefficient current generating circuit and the current summing circuit respectively; the positive temperature coefficient current generating circuit is used for generating a positive temperature coefficient current; the negative temperature coefficient current generating circuit is connected with the current summing circuit; the negative temperature coefficient current generating circuit is used for generating a negative temperature coefficient current; the current summing circuit is connected with the positive temperature coefficient current generating circuit and the negative temperature coefficient current generating circuit respectively; the current summing circuit is used for mirroring the positive temperature coefficient current and the negative temperature coefficient current according to a corresponding preset ratio, summing the mirrored positive temperature coefficient current and the mirrored negative temperature coefficient current, and outputting a zero temperature coefficient current after the summing. The embodiment of the application mirrors and sums the positive temperature coefficient current generated by the positive temperature coefficient current generating circuit and the negative temperature coefficient current generated by the negative temperature coefficient current generating circuit according to a corresponding preset ratio through the current summing circuit, to generate a zero temperature coefficient current. Since the size of the zero temperature coefficient current remains constant without being changed with temperature, the problem that the output current is significantly changed with temperature and the temperature characteristic is poor is avoided.

[0053] Referring to Figure 2 , a structure schematic diagram of a current source circuit of the embodiment of the application is shown, and the positive temperature coefficient current generating circuit comprises a first switch tube 11, a second switch tube 12, a third switch tube 13, a fourth switch tube 14 and a first resistor 15.

[0054] The input end of the first switch tube 11 is connected with a power supply 40.

[0055] The input end of the second switch tube 12 is connected with the power supply 40, and the control end of the second switch tube 12 is connected with the control end of the first switch tube 11.

[0056] The input end of the third switch tube 13 is connected with the output end of the first switch tube 11.

[0057] The input end of the fourth switch tube 14 is connected with the control end of the third switch tube 13 and the output end of the second switch tube 12 respectively, the control end of the fourth switch tube 14 is connected with the output end of the second switch tube 12 and the input end of the fourth switch tube 14 respectively, and the output end of the fourth switch tube 14 is connected with the control end of the third switch tube 13 and the ground respectively.

[0058] One end of the first resistor 15 is connected with the output end of the second switch tube 12 and the control end of the fourth switch tube 14 respectively, and the other end of the first resistor 15 is connected with the control end of the third switch tube 13 and the input end of the fourth switch tube 14 respectively.

[0059] The first switch tube 11 and the second switch tube 12 constitute a current mirror structure for copying the positive temperature coefficient current to other branches, the first switch tube 11 is a reference transistor, the second switch tube 12 copies the current of the first switch tube 11, the current mirror can "copy" or "mirror" one reference current to another branch, realizing the accurate transmission or multiplication of the current.

[0060] In the embodiment of the present application, the first switch tube 11 and the second switch tube 12 are in the saturation region, and the third switch tube 13 and the fourth switch tube 14 are in the sub-threshold region.

[0061] The switch tube can be a MOS tube (Metal-Oxide-Semiconductor Field-Effect Transistor), the gate of the first switch tube 11 is short-circuited with the drain of the first switch tube 11, the gate of the first switch tube 11 is connected with the gate of the second switch tube 12, and the source of the first switch tube 11 and the source of the second switch tube 12 are both connected with the power supply 40.

[0062] The first switch tube 11 and the second switch tube 12 are in the saturation region, when the MOS tube works in the saturation region, the drain current of the MOS tube basically no longer increases significantly with the increase of the drain-source voltage, but is mainly controlled by the gate-source voltage, which makes the MOS tube in this region exhibit the characteristics similar to "current source".

[0063] The third switch tube 13 and the fourth switch tube 14 are in the sub-threshold region, when the MOS tube works in the sub-threshold region, the drain current is in exponential relationship with the gate-source voltage.

[0064] The voltage drop on the first resistor 15 is the gate-source voltage difference of the third switch tube 13 and the fourth switch tube 14, that is: ΔV GS = V GS4 -V GS3 = I D4 R1, wherein ΔV GS is the gate-source voltage difference of the third switch tube 13 and the fourth switch tube 14, V GS4 is the gate-source voltage of the fourth switch tube 14, V GS3 is the gate-source voltage of the third switch tube 13, R1 is the resistance value of the first resistor 15, and I D4 is the drain voltage of the fourth switch tube 14.

[0065] The channel of the third switch tube 13 and the fourth switch tube 14 is set to be long enough to reduce the channel modulation effect, so that the threshold voltage VTH3 of the third switch tube 13 and the threshold voltage VTH4 of the fourth switch tube 14 are equal, the width-length ratio of the third switch tube 13 is K1, and the width-length ratio of the fourth switch tube 14 is K2, where the width-length ratio refers to the ratio of the width (W) of the MOS tube channel to the channel length (L), that is:

[0066] Since ΔV GS = V GS4 -V GS3 = I D4 R1, that is:

[0067] Where I D3 is the drain current of the third switch tube 13, V T is the thermal voltage, and η is the sub-threshold slope factor. According to the MOS tube sub-threshold region current formula, the current is exponentially related to the gate-source voltage, and by combining the sub-threshold region current formulas of the third switch tube 13 and the fourth switch tube 14, the relationship between the drain current of the third switch tube 13 and the drain current of the fourth switch tube 14 is obtained.

[0068] The derivative of the above formula with respect to I D4 is equal to 0, which gives:

[0069]

[0070] That is The solution is Since V T is the thermal voltage, where K is the Boltzmann constant, q is the electron charge, and V T is the voltage, which is positively related to temperature, so I D4 is a positive temperature coefficient current.

[0071] The current flowing through the second switch tube 12, the first resistor 15, and the fourth switch tube 14 branch is a positive temperature coefficient current, and the current flowing through the first switch tube 11 and the third switch tube 13 is also a positive temperature coefficient current.

[0072] The first switch tube 11 and the second switch tube 12 form a current mirror, and the first switch tube 11 and the second switch tube 12 are in the saturation region, so that the drain current of the first switch tube 11 and the second switch tube 12 does not significantly increase with the increase of the drain-source voltage, but is mainly controlled by the gate-source voltage, and the third switch tube 13 and the fourth switch tube 14 are in the sub-threshold region, so that the drain current of the third switch tube 13 and the fourth switch tube 14 is exponentially related to the gate-source voltage, thereby generating a positive temperature coefficient current through the first resistor 15, the third switch tube 13, and the fourth switch tube 14.

[0073] In the embodiment of the present application, the negative temperature coefficient current generating circuit comprises a fifth switch tube 21, a sixth switch tube 22, a seventh switch tube 23, an eighth switch tube 24, a ninth switch tube 25 and a second resistor 26.

[0074] The input end of the fifth switch tube 21 is connected with the power supply 40, and the control ends of the fifth switch tube 21 are respectively connected with the control end of the first switch tube 11 and the control end of the second switch tube 12.

[0075] The input end of the sixth switch tube 22 is connected with the output end of the fifth switch tube 21, and the output end of the sixth switch tube 22 is grounded.

[0076] The input end of the seventh switch tube 23 is connected with the power supply 40, and the output end of the seventh switch tube 23 is respectively connected with the control end of the sixth switch tube 22 and the ground.

[0077] The input end of the eighth switch tube 24 is connected with the power supply 40, and the control end of the eighth switch tube 24 is connected with the control end of the seventh switch tube 23.

[0078] The input end of the ninth switch tube 25 is connected with the output end of the eighth switch tube 24, and the control end of the ninth switch tube 25 is respectively connected with the output end of the seventh switch tube 23 and the control end of the sixth switch tube 22.

[0079] One end of the second resistor 26 is respectively connected with the output end of the sixth switch tube 22 and the ground, and the other end of the second resistor 26 is respectively connected with the control end of the sixth switch tube 22, the output end of the seventh switch tube 23 and the control end of the ninth switch tube 25.

[0080] The gate of the eighth switch tube 24 is short-circuited with the drain of the eighth switch tube 24, the gate of the eighth switch tube 24 is connected with the gate of the seventh switch tube 23, the source of the eighth switch tube 24 and the source of the seventh switch tube 23 are both connected with the power supply 40, the eighth switch tube 24 and the seventh switch tube 23 constitute a current mirror structure, which functions to copy the negative temperature coefficient current to other branches, the fifth switch tube 21 serves as the current source load of the sixth switch tube 22, the ninth switch tube 25 provides a suitable bias point for the sixth switch tube 22, and the sixth switch tube 22 and the second resistor 26 generate the negative temperature coefficient current.

[0081] In the embodiment of the present application, the fifth switch tube 21, the seventh switch tube 23, the eighth switch tube 24 and the ninth switch tube 25 are in the saturation region, and the sixth switch tube 22 is in the sub-threshold region.

[0082] The sixth switch tube 22 is in the sub-threshold region, the gate-source voltage of the sixth switch tube 22 is determined by the voltage drop on the second resistor 26, and the drain current of the sixth switch tube 22 is exponentially related to the temperature change.

[0083] When the sixth switch tube 22 works in the sub-threshold region, and the gate-source voltage of the sixth switch tube 22 approaches its threshold voltage, the sixth switch tube 22 starts to conduct, the current is small, and the drain current of the sixth switch tube 22 is:

[0084]

[0085] wherein, I D6 is the drain current of the sixth switch tube 22, μ is the mobility of the carrier, C ox is the gate oxide layer capacitance, V T is the thermal voltage, η is the sub-threshold slope factor, W is the width of the MOS gate, L is the length of the MOS gate, V GS is the gate-source voltage of the MOS, V TH is the threshold voltage of the MOS.

[0086] From the above formula, it can be obtained that: It can be seen from the formula that when the MOS works in the sub-threshold region, the value of the threshold voltage VTH will become smaller and smaller with the increase of the working temperature, that is, VGS decreases with the increase of the temperature, and presents a negative temperature characteristic.

[0087] The drain current of the sixth switch tube 22 is equal to:

[0088]

[0089] VGS6 is a negative temperature coefficient voltage, and the temperature coefficient of the resistor R2 is ignored, so that I D6 is a negative temperature coefficient current.

[0090] The current flowing through the seventh switch tube 23, the eighth switch tube 24, the ninth switch tube 25 and the second resistor 26 is a negative temperature coefficient current.

[0091] The fifth switch tube 21, the seventh switch tube 23, the eighth switch tube 24 and the ninth switch 25 are in the saturation region, and the sixth switch tube 22 is in the sub-threshold region, and the negative temperature coefficient current can be generated through the sixth switch tube 22 and the second resistor 26.

[0092] In the embodiment of the present application, the current summation circuit 30 comprises a first current mirror branch 31 and a second current mirror branch 32;

[0093] The first current mirror branch 31 is connected with the positive temperature coefficient current generation circuit 10, and is used for outputting the positive temperature coefficient current after mirroring according to a corresponding preset proportion;

[0094] The second current mirror branch 32 is connected with the negative temperature coefficient current generating circuit 20 and the first current mirror branch 31 respectively, and is used for mirroring and outputting the negative temperature coefficient current according to a corresponding preset proportion, so that the mirrored positive temperature coefficient current and the mirrored negative temperature coefficient current are added to generate the zero temperature coefficient current.

[0095] The first current mirror branch 31 and the positive temperature coefficient current generating circuit 10 constitute a current mirror structure, the first current mirror branch 31 copies the positive temperature coefficient current IPTAT generated by the positive temperature coefficient current generating circuit 10 N times to the first current mirror branch 31, and N times of the positive temperature coefficient current NIPTAT is obtained.

[0096] The second current mirror branch 32 and the negative temperature coefficient current generating circuit 20 constitute a current mirror structure, the second current mirror branch 32 copies the negative temperature coefficient current ICTAT generated by the negative temperature coefficient current generating circuit 20 M times to the second current mirror branch 32, and M times of the negative temperature coefficient current MICTAT is obtained.

[0097] The N times of the positive temperature coefficient current and the M times of the negative temperature coefficient current are added with the coefficients of M and N to cancel each other to obtain the zero temperature coefficient current. The first current mirror branch 31 and the second current mirror branch 32 respectively copy the positive temperature coefficient current IPTAT and the negative temperature coefficient current ICTAT according to different proportions and then superimpose to generate the zero temperature coefficient current.

[0098] In the embodiment of the application, the first current mirror branch 31 includes a tenth switch tube 311.

[0099] The input end of the tenth switch tube 311 is connected with the power supply 40, the control end of the tenth switch tube 311 is connected with the control end of the first switch tube 11 and the control end of the second switch tube 12 respectively; and is used for mirroring and outputting the positive temperature coefficient current according to a corresponding preset proportion.

[0100] The tenth switch tube 311 and the second switch tube 12 of the positive temperature coefficient current generating circuit 10 constitute a current mirror, since the current flowing through the second switch tube 12 is the positive temperature coefficient current, the tenth switch tube 311 mirrors and outputs the positive temperature coefficient current according to a corresponding preset proportion, for example, copies the positive temperature coefficient current N times.

[0101] The tenth switch tube 311 and the second switch tube 12 constitute a current mirror structure, the second switch tube 12 is a reference tube of the current mirror, and the tenth switch tube 311 is a copy tube of the current mirror, so that the positive temperature coefficient current is mirrored according to a corresponding preset proportion.

[0102] In the embodiment of the application, the second current mirror branch 32 includes an eleventh switch tube 321;

[0103] The input end of the eleventh switch tube 321 is connected with the power supply 40, the control end of the eleventh switch tube 321 is connected with the control end of the seventh switch tube 23 and the control end of the eighth switch tube 24 respectively, and the output end of the eleventh switch tube 321 is connected with the output end of the tenth switch tube 311; and the negative temperature coefficient current is output after being mirrored according to a corresponding preset ratio.

[0104] The eleventh switch tube 321 and the seventh switch tube 23 of the negative temperature coefficient current generating circuit 20 constitute a current mirror, since the current flowing through the seventh switch tube 23 is the negative temperature coefficient current, the eleventh switch tube 321 outputs the negative temperature coefficient current after mirroring according to a corresponding preset ratio, for example, M times of the negative temperature coefficient current.

[0105] The eleventh switch tube 321 and the seventh switch tube 23 constitute a current mirror structure, the seventh switch tube 23 is a reference tube of the current mirror, and the eleventh switch tube 321 is a copy tube of the current mirror, so that the negative temperature coefficient current is mirrored according to a corresponding preset ratio.

[0106] The output end of the eleventh switch tube 321 is connected with the output end of the tenth switch tube 311, M times of the negative temperature coefficient current output by the eleventh switch tube 321 and N times of the positive temperature coefficient current output by the tenth switch tube 311 are added at the connection position of the output end of the eleventh switch tube 321 and the output end of the tenth switch tube 311, to generate a zero temperature coefficient current.

[0107] Exemplarily, the mirroring ratio, i.e., the copy multiple, can be determined through a simulation experiment, by changing the temperature, the curve of the positive temperature coefficient current generated by the positive temperature coefficient current generating circuit 10 and the curve of the negative temperature coefficient current generated by the negative temperature coefficient current generating circuit 20 at different temperatures are determined, the slope of the curve of the positive temperature coefficient current and the slope of the curve of the negative temperature coefficient current are determined, according to the slope of the curve of the positive temperature coefficient current and the slope of the curve of the temperature coefficient current, the mirroring ratio N of the positive temperature coefficient current and the mirroring ratio M of the negative temperature coefficient current are determined, so that N times of the positive temperature coefficient current and M times of the negative temperature coefficient current are added at the connection position of the output end of the eleventh switch tube 321 and the output end of the tenth switch tube 311, to generate a zero temperature coefficient current.

[0108] In the embodiment of the application, the tenth switch tube 311 is a plurality of parallel switch tubes, and the eleventh switch tube 321 is a plurality of parallel switch tubes.

[0109] The tenth switch tube 311 and the second switch tube 12 constitute a current mirror structure, the eleventh switch tube 321 and the seventh switch tube 23 constitute a current mirror structure, the tenth switch tube 311 is provided as a plurality of parallel switch tubes, the eleventh switch tube 321 is provided as a plurality of parallel switch tubes, the current of the second switch tube 12, i.e. the positive temperature coefficient current, can be copied by the tenth switch tube 311 at a preset proportion, the current of the seventh switch tube 23, i.e. the negative temperature coefficient current, can be copied by the eleventh switch tube 321 at a preset proportion, so that the positive temperature coefficient current copied at a preset proportion and the negative temperature coefficient copied at a preset proportion are added, and a zero temperature coefficient current is obtained.

[0110] In the embodiment of the present application, the first switch tube 11, the second switch tube 12, the third switch tube 13, the fourth switch tube 14, the fifth switch tube 21, the sixth switch tube 22, the seventh switch tube 23, the eighth switch tube 24, the ninth switch tube 25, the tenth switch tube 311 and the eleventh switch tube 321 are MOS tubes.

[0111] The behavior of the MOS tube in the subthreshold region has a unique temperature dependence. Specifically, the negative temperature characteristic of the gate-source voltage in the subthreshold region means that as the temperature rises, the required gate-source voltage will decrease in order to maintain the same subthreshold current. The embodiment of the present application utilizes the negative temperature characteristic of the gate-source voltage in the subthreshold region of the MOS tube to generate a negative temperature coefficient current, and at the same time utilizes the positive temperature characteristic of the thermal voltage to generate a positive temperature coefficient current. The positive temperature coefficient current and the negative temperature coefficient current pass through the first current mirror branch 31 and the second current mirror branch 32 of the current summing circuit 30 respectively to obtain two weighted currents, i.e. N times the positive temperature coefficient current (NIPTAT) and M times the negative temperature coefficient current (MICTAT). The two weighted currents are mutually compensated to obtain a zero temperature coefficient current.

[0112] The zero temperature coefficient current source circuit of the embodiment of the present application does not need to rely on bipolar transistors, but is based on the subthreshold characteristics of MOS transistors to generate and sum positive and negative temperature coefficient currents. By optimizing the current mirror structure and the proportion relationship, a stable zero temperature drift reference current is generated for biasing an oscillator, which not only effectively reduces the frequency drift with temperature, but also significantly reduces the static power consumption and layout area of the circuit, and is more suitable for low-power integrated circuit applications.

[0113] The current source circuit of the embodiment of the present application comprises a positive temperature coefficient current generating circuit, a negative temperature coefficient current generating circuit and a current summing circuit; the positive temperature coefficient current generating circuit is connected with the negative temperature coefficient current generating circuit and the current summing circuit respectively; the positive temperature coefficient current generating circuit is used for generating a positive temperature coefficient current; the negative temperature coefficient current generating circuit is connected with the current summing circuit; the negative temperature coefficient current generating circuit is used for generating a negative temperature coefficient current; the current summing circuit is connected with the positive temperature coefficient current generating circuit and the negative temperature coefficient current generating circuit respectively; the current summing circuit is used for mirroring the positive temperature coefficient current and the negative temperature coefficient current according to a corresponding preset ratio, summing the mirrored positive temperature coefficient current and the mirrored negative temperature coefficient current, and outputting a zero temperature coefficient current after the zero temperature coefficient current is generated. The embodiment of the present application mirrors and sums the positive temperature coefficient current generated by the positive temperature coefficient current generating circuit and the negative temperature coefficient current generated by the negative temperature coefficient current generating circuit according to a corresponding preset ratio through the current summing circuit, and generates a zero temperature coefficient current. Since the size of the zero temperature coefficient current remains constant without temperature change, the problem that the output current changes significantly with temperature and the temperature characteristic is poor is avoided.

[0114] The embodiment of the present application also provides an oscillator comprising the current source circuit according to any one of the above.

[0115] Reference Figure 2 The oscillator comprises an inverter chain circuit 50, and the output end of the current summing circuit 30 is connected with the inverter chain circuit 50. The current summing circuit 30 adds the positive temperature coefficient current and the negative temperature coefficient current through different ratios to obtain a zero temperature coefficient current, and outputs the zero temperature coefficient current to the inverter chain circuit 50 of the oscillator. The good temperature characteristic of the zero temperature coefficient current ensures that the working current of each inverter in the ring oscillator changes little with temperature, thereby keeping the delay time stable, reducing the temperature drift of the frequency, and maintaining the constant of the oscillation frequency. Meanwhile, the third switch tube 13, the fourth switch tube 14 and the sixth switch tube 22 are designed to be in the sub-threshold region state, the sub-threshold region tube current is significantly smaller than the saturation region current, and the power consumption of the circuit is reduced.

[0116] The negative temperature coefficient voltage characteristic of the gate-source voltage of the sub-threshold region MOS tube and the positive temperature coefficient voltage of the difference between the gate-source voltages of two sub-threshold region MOS tubes are utilized to generate a zero temperature coefficient current, reduce the drift of the oscillator frequency with temperature, and reduce the overall circuit power consumption.

[0117] The oscillator can be a ring oscillator, the ring oscillator comprising an inverter chain circuit 50 and a current source circuit connected with the inverter chain circuit 50; the current source circuit comprising a positive temperature coefficient current generating circuit 10, a negative temperature coefficient current generating circuit 20 and a current summing circuit 30; the inverter chain circuit 50 comprising a twelfth switch tube 51, a thirteenth switch tube 52, a fourteenth switch tube 53, a fifteenth switch tube 54, a sixteenth switch tube 55, a seventeenth switch tube 56, a first capacitor 57, a second capacitor 58 and a third capacitor 59.

[0118] The current source circuit comprises a positive temperature coefficient current generating circuit, a negative temperature coefficient current generating circuit and a current summing circuit; the positive temperature coefficient current generating circuit is connected with the negative temperature coefficient current generating circuit and the current summing circuit respectively; the positive temperature coefficient current generating circuit is used for generating a positive temperature coefficient current; the negative temperature coefficient current generating circuit is connected with the current summing circuit; the negative temperature coefficient current generating circuit is used for generating a negative temperature coefficient current; the current summing circuit is connected with the positive temperature coefficient current generating circuit and the negative temperature coefficient current generating circuit respectively; the current summing circuit is used for mirroring the positive temperature coefficient current and the negative temperature coefficient current according to a corresponding preset ratio, summing the mirrored positive temperature coefficient current and the mirrored negative temperature coefficient current, and outputting a zero temperature coefficient current. The embodiment of the present application mirrors and sums the positive temperature coefficient current generated by the positive temperature coefficient current generating circuit and the negative temperature coefficient current generated by the negative temperature coefficient current generating circuit according to a corresponding preset ratio through the current summing circuit, to generate a zero temperature coefficient current. Since the size of the zero temperature coefficient current remains constant without being changed with temperature, the problem that the output current changes significantly with temperature and the temperature characteristic is poor is avoided.

[0119] The embodiments in the specification are described in a progressive manner, and each embodiment focuses on the difference from other embodiments. The same or similar parts of each embodiment can be referred to each other.

[0120] Those skilled in the art should understand that the embodiments of the present application can be provided as a method, device or computer program product. Therefore, the embodiments of the present application can be in the form of a complete hardware embodiment, a complete software embodiment or an embodiment combining software and hardware aspects. Moreover, the embodiments of the present application can be in the form of a computer program product implemented on one or more computer usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer usable program code.

[0121] The embodiments of the present application are described with reference to the flowchart illustrations and / or block diagrams of the methods, terminal devices (systems) and computer program products according to the embodiments of the present application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing terminal devices to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing terminal devices, create means for implementing the functions specified in the flowchart illustrations and / or block diagrams. Figure 1 one or more functions specified in the flowchart illustrations and / or block diagrams. Figure 1 one or more functions specified in the flowchart illustrations and / or block diagrams.

[0122] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing terminal devices to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instructions which implement the function specified in the flowchart illustrations and / or block diagrams. Figure 1 one or more functions specified in the flowchart illustrations and / or block diagrams. Figure 1 one or more functions specified in the flowchart illustrations and / or block diagrams.

[0123] These computer program instructions can also be loaded onto a computer or other programmable data processing terminal devices, such that a series of operational steps are carried out on the computer or other programmable terminal devices to produce a computer implemented process so that the instructions executed on the computer or other programmable terminal devices provide steps for implementing the functions specified in the flowchart illustrations and / or block diagrams. Figure 1 one or more functions specified in the flowchart illustrations and / or block diagrams. Figure 1 one or more functions specified in the flowchart illustrations and / or block diagrams.

[0124] Although preferred embodiments of the present application have been described, those skilled in the art will be able to make additional modifications and variations to the embodiments without departing from the scope of the present application. Accordingly, the appended claims are intended to encompass all such modifications and variations as falling within the scope of the embodiments of the present application.

[0125] Finally, it is to be understood that the phraseology or terminology such as "first" and "second" etc. used herein is merely intended to differentiate one entity or operation from another entity or operation, without necessarily requiring or implying any actual such relationship or order between such entities or operations. Moreover, the terms "comprising", "including", or any other closure, are intended to cover the non-exclusive inclusion such that a process, method, article, or apparatus that comprises a list of elements does not include those elements alone but can include other elements not expressly listed or even include elements inherent in such process, method, article, or apparatus. Without more limitations, the element defined by the statement "comprising a" does not exclude the presence of additional identical elements in the process, method, article, or apparatus including the element.

[0126] The above describes in detail the current source circuit and oscillator provided by the present application. The principles and implementation modes of the present application are described by using specific examples. The above description of the embodiments is only used to help understand the method of the present application and its core idea. Meanwhile, for those skilled in the art, the specific implementation modes and application ranges can be changed according to the idea of the present application. In summary, the content of the specification should not be understood as a limitation of the present application.

Claims

1. A current source circuit, characterized by, The circuit comprises a positive temperature coefficient current generating circuit, a negative temperature coefficient current generating circuit and a current summing circuit; The positive temperature coefficient current generating circuit is connected with the negative temperature coefficient current generating circuit and the current summing circuit respectively; For generating a positive temperature coefficient current; The negative temperature coefficient current generating circuit is connected with the current summing circuit; For generating a negative temperature coefficient current; The current summing circuit is connected with the positive temperature coefficient current generating circuit and the negative temperature coefficient current generating circuit respectively; for mirroring the positive temperature coefficient current and the negative temperature coefficient current according to a corresponding preset ratio, summing the mirrored positive temperature coefficient current and the mirrored negative temperature coefficient current, and outputting after generating a zero temperature coefficient current.

2. The current source circuit of claim 1, wherein, The positive temperature coefficient current generating circuit comprises a first switch tube, a second switch tube, a third switch tube, a fourth switch tube and a first resistor; The input end of the first switch tube is connected with a power supply; The input end of the second switch tube is connected with the power supply, and the control end of the second switch tube is connected with the control end of the first switch tube; The input end of the third switch tube is connected with the output end of the first switch tube; The input end of the fourth switch tube is connected with the control end of the third switch tube and the output end of the second switch tube respectively, the control end of the fourth switch tube is connected with the output end of the second switch tube and the input end of the fourth switch tube respectively, and the output end of the fourth switch tube is connected with the control end of the third switch tube and the ground respectively; One end of the first resistor is connected with the output end of the second switch tube and the control end of the fourth switch tube respectively, and the other end of the first resistor is connected with the control end of the third switch tube and the input end of the fourth switch tube respectively.

3. The current source circuit of claim 2, wherein, The first switch tube and the second switch tube are in the saturation region, and the third switch tube and the fourth switch tube are in the sub-threshold region.

4. The current source circuit of claim 2, wherein, The negative temperature coefficient current generating circuit comprises a fifth switch tube, a sixth switch tube, a seventh switch tube, an eighth switch tube, a ninth switch tube and a second resistor; The input end of the fifth switch tube is connected with the power supply, and the control end of the fifth switch tube is connected with the control end of the first switch tube and the control end of the second switch tube respectively; The input end of the sixth switch tube is connected with the output end of the fifth switch tube, and the output end of the sixth switch tube is grounded; The input end of the seventh switch tube is connected with the power supply, and the output end of the seventh switch tube is connected with the control end of the sixth switch tube and the ground respectively; The input end of the eighth switch tube is connected with the power supply, and the control end of the eighth switch tube is connected with the control end of the seventh switch tube; The input end of the ninth switch tube is connected with the output end of the eighth switch tube, and the control end of the ninth switch tube is connected with the output end of the seventh switch tube and the control end of the sixth switch tube respectively; One end of the second resistor is connected with the output end of the sixth switch tube and the ground respectively, and the other end of the second resistor is connected with the control end of the sixth switch tube, the output end of the seventh switch tube and the control end of the ninth switch tube respectively.

5. The current source circuit of claim 4, wherein, The fifth switch tube, the seventh switch tube, the eighth switch tube and the ninth switch tube are in a saturation region, and the sixth switch tube is in a sub-threshold region.

6. The current source circuit of claim 4, wherein, The current summing circuit includes a first current mirror branch and a second current mirror branch. The first current mirror branch is connected with the positive temperature coefficient current generating circuit, and is configured to mirror and output the positive temperature coefficient current according to a corresponding preset ratio. The second current mirror branch is connected with the negative temperature coefficient current generating circuit and the first current mirror branch respectively, and is configured to mirror and output the negative temperature coefficient current according to a corresponding preset ratio, so that the mirrored positive temperature coefficient current and the mirrored negative temperature coefficient current are added to generate a zero temperature coefficient current.

7. The current source circuit of claim 6, wherein, The first current mirror branch includes a tenth switch tube. An input end of the tenth switch tube is connected with the power supply, and control ends of the tenth switch tube are connected with control ends of the first switch tube and the second switch tube respectively. The first current mirror branch is configured to mirror and output the positive temperature coefficient current according to a corresponding preset ratio.

8. The current source circuit of claim 7, wherein, The second current mirror branch includes an eleventh switch tube. An input end of the eleventh switch tube is connected with the power supply, control ends of the eleventh switch tube are connected with control ends of the seventh switch tube and the eighth switch tube respectively, and an output end of the eleventh switch tube is connected with an output end of the tenth switch tube.

9. The current source circuit of claim 8, wherein, The tenth switch tube is a plurality of parallel switch tubes, and the eleventh switch tube is a plurality of parallel switch tubes.

10. The current source circuit of claim 8, wherein, The first switch tube, the second switch tube, the third switch tube, the fourth switch tube, the fifth switch tube, the sixth switch tube, the seventh switch tube, the eighth switch tube, the ninth switch tube, the tenth switch tube and the eleventh switch tube are MOS tubes.

11. An oscillator characterized by The current source circuit includes the current source circuit according to any one of claims 1 to 10. The current source circuit includes the current source circuit according to any one of claims 1 to 10.

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