CN105932976A - Temperature compensation circuit for crystal oscillator - Google Patents

Abstract

The invention belongs to the field of integrated circuits, and specifically relates to a temperature compensation circuit for a crystal oscillator. The temperature compensation circuit generates reference voltage Vref of a third power function for temperature, and controls the magnitude, monomial coefficient, quadratic coefficient and ternary coefficient of the output reference voltage under the actions of control signals Cont-Rm1, Cont-Rm2, Cont-Rm3 and Cont-NL, so as to change the temperature coefficient and the zero temperature coefficient point of the reference voltage according to the temperature-frequency characteristics of different crystals. The reference voltage controls the capacitance of a variable capacitance diode, so as to accurately compensate the offset of the oscillation frequency of the crystal oscillator due to temperature changes and improve the temperature stability of the frequency. The temperature compensation circuit generates the reference voltage with different temperature coefficients and zero temperature coefficient points for crystals with different temperature characteristics, is high in flexibility, high in compensation precision, simple in structure and low in cost, and facilities miniaturization and integration.

Description

A kind of temperature-compensation circuit for crystal oscillator

Technical field

The invention belongs to integrated circuit fields, relate to the temperature-compensation circuit of crystal oscillator, it is a kind of right to be specially Temperature is the reference voltage generating circuit of cube function.

Background technology

Crystal oscillator is widely used in portable electric appts and radio communication skill as stable frequency source The fields such as art, its frequency is to weigh the important indicator that crystal oscillator performance is good and bad to the degree of stability of variations in temperature One of.Temperature compensating crystal oscillator reduces crystal oscillator output frequency because of temperature by temperature compensation network The skew that change produces, thus improve frequency stability.

For being usually used in the AT cut type quartz resonator of crystal oscillator, the relation of its resonant frequency and temperature is used Cubic curve describes, particularly as follows:

F (T)=f₀+A·(T-T₀)+B·(T-T₀)²+C·(T-T₀)³ (1)

Wherein, T is absolute temperature, and f is the resonant frequency at temperature T, f₀Be temperature be T₀Time nominal frequency, T₀Being reference temperature, be also characteristic using temperature-frequency point of inflexion on a curve, A, B, C are temperature-frequency relation respectively The coefficient of first order, quadratic term, cubic term in formula.

In order to compensate the skew that the resonant frequency of crystal produces because of variations in temperature, crystal resonator branch road is connected One varactor, the capacitance of varactor, by the Control of Voltage at its two ends, changes change by changing voltage Hold the capacitance of diode, thus change the load capacitance of resonator, make the resonant frequency of resonator to reducing frequency The direction change of rate skew, reduces frequency offset, improves the frequency stability of crystal oscillator.

The change approximate linear function of resonant frequency of a crystal is described, specifically by the voltage that controls of varactor For:

F (V)=f₀-G(V-V₀) (2)

Wherein, G is gain, V₀It it is reference voltage.

In order to compensate the side-play amount of resonator resonant frequency, it is necessary to have:

Δ f (T)=-Δ f (V) (3)

Then the relational representation controlling voltage and temperature of varactor is:

V (T)=V₀+a·(T-T₀)+b·(T-T₀)²+c·(T-T₀)³ (4)

Wherein, a=A/G, b=B/G, c=C/G, this voltage versus temperature is cube functional relationship, crystal oscillating circuit Technique for temperature compensation it is crucial that producing is control voltage V (T) of cube function to temperature, make crystal oscillator Frequency-temperature characteristic curve close to preferable f (T)=f₀。

The temperature compensation technology of crystal oscillating circuit has analog temperature compensation, design and temperature of micro at present The technology such as compensation.Design technology is owing to have employed A/D, D/A, memorizer, temperature sensor etc. Module makes the relatively costly of system, and owing to frequency hopping phenomenon adds the phase noise of crystal oscillating circuit； Temperature of micro compensation technique is especially owing to have employed the peripheries such as microprocessor, A/D, D/A and wave filter Circuit module is difficult to realize integrated and miniaturization.

Analog temperature compensation technology is more prone to continuous print voltage, and being easily integrated and miniaturization.Current In analog temperature compensation technology, mostly use the mode of segmented compensation, produce respectively high temperature section and low-temperature zone The voltage compensated, obtain after summation in the range of total temperature to temperature be cubic function relation compensation electricity Pressure, and use each term coefficient in the mode adjustable type (4) of parameter read-in RAM and PROM.Existing Analog temperature compensation technology, not only circuit structure is complicated, and circuit power consumption is big, is unfavorable for the little of integrated chip Typeization realizes, and is difficult to control each the adjustable requirement of term coefficient of voltage, it is impossible to be applicable to different Crystal.

Summary of the invention

For existing crystal oscillator temperature compensation network cost height, circuit structure is complicated, it is integrated and little to be difficult to The shortcoming of type, the invention provides a kind of temperature-compensation circuit for crystal oscillator, this temperature-compensating Circuit is cube letter to temperature according to the temperature characterisitic of different crystal, generation size and temperature coefficient adjustable The reference voltage of number, this reference voltage changes the load capacitance of crystal by the capacitance controlling varactor, Thus compensate the skew that crystal oscillation frequency produces because of variations in temperature, improve frequency stability.

Technical scheme is as follows:

A kind of temperature-compensation circuit for crystal oscillator, including start-up circuit, adjustable PTAT (proportional to absolute temperature) current source, adjustable CTAT (complementary to Absolute temperature) current source, adjustable non-linear current source, electric current summation module and adjustable Current-voltage converter.

Start-up circuit, in power supply electrifying moment, provides the DC operation of non-zero to adjustable PTAT current source Point.After circuit start completes, start-up circuit cuts out, and does not consume electric current；

Adjustable PTAT current source produces the PTAT current that size is different with Monomial coefficient；

Adjustable CTAT current source produces the CTAT current that size is different with Monomial coefficient；

Adjustable non-linear current source produces size, Monomial coefficient, quadratic term coefficient, cubic term coefficient the most not Same non-linear current；

Electric current summation module is to described PTAT current, CTAT current and non-linear current modulus, and it is right to produce Temperature is the electric current of cube function；

Adjustable current-voltage converter converts electrical current into voltage, and this voltage versus temperature is cube functional relationships System, for controlling the capacitance of varactor in crystal oscillator, compensates the frequency of oscillation of crystal because of temperature change Change the skew produced.

In control signal Cont_R_m1、Cont_R_m2、Cont_R_m3With under Cont_NL effect, regulate respectively PTAT current, CTAT current, the temperature coefficient of non-linear current and the size of reference voltage, thus root Size and the temperature coefficient of this reference voltage is regulated according to the characteristic using temperature-frequency of different crystal.

Further, described start-up circuit includes p-type metal-oxide-semiconductor MS1, MS2 and electric capacity C1.MS1 Grid meet V_A, miss the grid of MS2, source meets power supply VCC, and the grid of MS2 meet leakage and the electric capacity C1 of MS1 Anode, source meets power supply VCC, misses the grid of MN1, the negativing ending grounding current potential of electric capacity C1.

Further, described adjustable PTAT current source includes 4 p-type metal-oxide-semiconductors, respectively MP1, MP2, MP3 and MP4,4 N-type metal-oxide-semiconductors, respectively MN1, MN2, MN3 and MN4 with And the memristor network R of m × n memristor composition_m1, m ＞ 1, n ＞ 1.The source of MP1 meets power supply VCC, The form that grid and leakage connect with diode is connected together, and connects the source of MP3 and the grid of MP2；The source of MP2 With memristor network R_m1One end be connected, miss the source of MP4；The grid of MP3 and MP4 are connected together, leakage Being connected with the leakage of MN1 and MN2 respectively, the grid of MP3 the most also connect the leakage of MP3；The substrate of MP2 with Source is connected and eliminates body bias effect, and the substrate of MP1, MP3 and MP4 all meets power supply VCC；Memristor net Network R_m1Another termination power VCC；The leakage missing MP3 of MN1, source connects the leakage of MN3, and grid meet MN2 Grid and leakage；The leakage missing MP4 of MN2, source connects the leakage of MN4；The grid of MN3 with MN4 are connected, And connect the leakage of MN4, the source of MN3 and MN4 all earthing potentials；MN1, MN2, MN3 and MN4 Substrate all earthing potentials.

Further, in above-mentioned adjustable PTAT current source, p-type metal-oxide-semiconductor MP1, MP2 and memristor Network R_m1Produce the electric current of positive temperature coefficient, i.e. PTAT current；P-type metal-oxide-semiconductor MP3 and MP4 forms Current mirror；N-type metal-oxide-semiconductor MN1, MN2, MN3 and MN4 form common-source common-gate current mirror, altogether grid Pipe MN1 and MN2 has been effectively isolated the fluctuation of supply voltage, improves the PSRR of PTAT current source.

Further, described MP1 and MP2 is operated in subthreshold region, its number than for 1:N, i.e. MP1 by The metal-oxide-semiconductor composition of 1 unit, MP2 is composed in parallel by the metal-oxide-semiconductor of N number of unit, then its breadth length ratio is: (W/L)_MP1:(W/L)_MP2=1:N (N >=2).The electric current flowing through MP1 and MP2 is equal, and is all PTAT current.

By current-voltage correlation and the annexation of circuit of MP1 and MP2, this PTAT current is expressed as:

$I_{PTAT}=\frac{kT}{{\mathrm{qR}}_{m1}}lnN={\mathrm{\α}}_{11}T---\left(5\right)$

Wherein, I_PTATIt is PTAT current, α₁₁It it is the Monomial coefficient of PTAT current.

Described adjustable PTAT current source produces the size PTAT current different with Monomial coefficient by following Method realizes: memristor network R_m1It is made up of m × n memristor, internal with erasable circuit, by control Signal Cont_R processed_m1Control, it is achieved arbitrarily resistance, thus adjust the slope of PTAT current₁₁。

Consider that MP1 and MP2 does not mates and V_AAnd V_BThe unequal nonlinear characteristic caused, PTAT current It is expressed as:

I_PTAT=α₁₂T+α₁₂T² (6)

Wherein, α₁₂It it is the quadratic term coefficient of PTAT current.

Further, adjustable CTAT current source of the present invention includes p-type metal-oxide-semiconductor MP5 and MP6, N-type metal-oxide-semiconductor MN5, MN6, MN7 and MN9, amplifier OPA and m × n memristor composition Memristor network R_m2, m ＞ 1, n ＞ 1.The grid leak of MP5 is connected together with diode, and connects amplifier The in-phase input end of OPA, source and substrate meet power supply VCC；The grid of MP6 connect the outfan of amplifier OPA, Source connects the inverting input of amplifier OPA, and with memristor network R_m2One end be connected；Memristor network R_m2's The other end is connected with power supply VCC；MN5 and MN6 grid connect the grid of MN2 and MN4 respectively, MN5's Source connects the leakage of MN6, misses the leakage of MP5, the source earthing potential of MN6；The grid of MN7 and leakage are with diode The form connected is connected together, and connects the leakage of MP6, and source connects the leakage of MN9；The grid leak of MN9 connect together and It is connected with the source of MN7, source earthing potential；The substrate of MN5, MN6, MN7 and MN9 all earthing potentials.

Further, in described adjustable CTAT current source, MP5, amplifier OPA and memristor network R_m2Produce Raw CTAT current, MN5 and MN6 composition current mirror mirror image PTAT current provides direct current biasing to MP5, MN7 and MN9 composition current mirror does the load of MP6, exports CTAT current simultaneously.

Further, above-mentioned p-type metal-oxide-semiconductor MP5 is operated in subthreshold region, is used for producing CTAT voltage. For being operated in the metal-oxide-semiconductor of subthreshold region, when its electric current is fixed value, its gate source voltage V_sg5There is negative temperature Degree coefficient；The clamping function of amplifier OPA makes the current potential of its in-phase input end and inverting input equal；By The annexation of circuit, memristor network R_m2The voltage at two ends is V_sg5, so flowing through R_m2Electric current be V_sg5/R_m2, Due to V_sg5There is negative temperature coefficient, ignore R_m2Temperature coefficient time, flow through memristor network R_m2Electric current also There is negative temperature coefficient, be embodied as:

$I_{CTAT}=\frac{V_{sg5}}{R_{m2}}={\mathrm{\α}}_{21}T---\left(7\right)$

Wherein, I_CTATIt is CTAT current, α₂₁It it is the Monomial coefficient that varies with temperature of CTAT current.

Described adjustable CTAT current source produces the size CTAT current different with Monomial coefficient by following Method realizes: memristor network R_m2It is made up of m × n memristor, internal with erasable circuit, by control Signal Cont_R processed_m2Control, it is achieved arbitrarily resistance, thus adjust the slope of CTAT current₂₁。

Further, it is considered to V_sg5The nonlinear terms caused due to the temperature characterisitic of bias current, amplifier imbalance etc., CTAT current is expressed as:

I_CTAT=α₂₁T+α₂₂T² (8)

Wherein, α₂₂It it is the quadratic term coefficient that varies with temperature of CTAT current.

Described adjustable non-linear current source is by k the N-type metal-oxide-semiconductor of M1～Mk, the k of SW1～SWk Individual selection switchs and decoder S composition.The grid end of k the N-type metal-oxide-semiconductor of M1～Mk is with respective Source is respectively connected with, and drain terminal one end with the switch of SW1～SWk respectively is connected, substrate all with earth potential phase Even；The other end of k the selection switch of SW1～SWk is connected together and is connected with the leakage of MN8；Decoder Output signal Cont_1 of S～Cont_k control the switch of SW1～SWk respectively, and the input of decoder connects control Signal Cont_NL processed.

Further, k the N-type metal-oxide-semiconductor of described M1～Mk is operated in sub-threshold region, its electric current right and wrong Linear current, is embodied as:

$I_{Mk}={\mathrm{\μC}}_{ox}{\left(\frac{W}{L}\right)}_{Mk}(\mathrm{\η}-1){\left(\frac{kT}{q}\right)}^2\exp \left(\frac{-{\mathrm{qV}}_{th}}{\mathrm{\η}kT}\right)---\left(9\right)$

Wherein, I_MkBeing the electric current flowing through metal-oxide-semiconductor Mk, μ is carrier mobility, C_oxIt it is gate oxide list Position area capacitance, W is channel width, and L is channel length, and η is subthreshold obliquity factor, and q is electron charge, K is Boltzmann constant, and T is absolute temperature, V_thIt it is the threshold voltage of Mk.This electric current is the non-thread of temperature Property function, by this electric current Taylor series expansion to three rank items, ignores higher order term, then this non-linear current table It is shown as:

I_Mk=α₃₁T+α₃₂T²+α₃₃T³ (10)

Wherein, α₃₁It is non-linear current I_MkThe Monomial coefficient varied with temperature, α₃₂It is non-linear current I_MkWith The quadratic term coefficient of variations in temperature, α₃₃It is non-linear current I_MkThe cubic term coefficient varied with temperature.

Further, in k the N-type metal-oxide-semiconductor of M1～Mk, M1 is made up of 1 unit, and M2 is by two Individual unit composes in parallel, and Mk is composed in parallel by k unit, and their breadth length ratio meets: (W/L)_M1:(W/L)_M2: ...: (W/L)_Mk=1:2:...:k.It is all to be composed in parallel by identical unit due to M1～Mk, Its threshold voltage is identical, then the current ratio flowing through M1～Mk meets: I_M1:I_M2:...:I_Mk=1:2:...:k.

Further, output signal Cont_1 of decoder S～Cont_k only one of which signal at any time Effectively, thus switch SW1～SWk only one of which at any time and open, thus this moment only have M1～ A metal-oxide-semiconductor electric current in Mk can export, it may be assumed that

I_NL=α₃₁T+α₃₂T²+α₃₃T³ (11)

Described adjustable non-linear current source produces non-linear different with quadratic term coefficient of size, Monomial coefficient Electric current is realized by the following method: changes the control word of input signal Cont_NL of decoder S, then changes Control signal Cont_1 of switch～the effectiveness of Cont_k, thus change size and the temperature of non-linear current Coefficient.

Described electric current summation module includes N-type metal-oxide-semiconductor MN8, MN10, MN11 and MN12.Its In, MN7, MN8, MN9 and MN10 form common-source common-gate current mirror mirror image CTAT current, MN8 Grid connect the grid of MN7, source connects the leakage of MN10, misses the leakage of MN11；The grid of MN10 connect MN9's Grid, source earthing potential；In like manner, MN2, MN4, MN11 and MN12 form common-source common-gate current mirror mirror As PTAT current, the grid of MN11 connect the grid of MN2, and source connects the leakage of MN12, and the grid of MN12 meet MN4 Grid, miss the source of MN11, source earthing potential；The substrate of MN8, MN10, MN11 and MN12 is all Earthing potential, the leakage of MN8 simultaneously is connected with the leakage of MN11, and connects the outfan of non-linear current, is formed Reference current I_ref, this electric current is expressed as:

I_ref=I_PTAT+I_CTAT+I_NL=(α₁₁+α₂₁+α₃₁)T+(α₁₂+α₂₂+α₃₂)T²+α₃₃T³ (12)

Described adjustable current-voltage converter includes the memristor network R of m × n memristor composition_m3.Memristor Device network R_m3A termination power VCC, another termination MN8 leakage, then reference voltage V_refIt is expressed as:

V_ref=V_DD-R_m3[(α₁₁+α₂₁+α₃₁)T+(α₁₂+α₂₂+α₃₂)T²+α₃₃T³] (13)

Memristor network R_m3Internal with erasable circuit, by control signal Cont_R_m3Control, with realize Arbitrarily resistance, thus according to the characteristic of varactor, regulate reference voltage V_refSize.

Further, the temperature characterisitic of said reference voltage does not accounts for the temperature characterisitic of memristor, in reality, Memristor has temperature characterisitic, it is contemplated that after the temperature characterisitic of memristor, and reference voltage can be expressed as:

$V_{ref}=V_{DD}-R_{m3}\[\frac{{\mathrm{\ΔV}}_{gs}}{R_{m1}}+\frac{V_{sg5}}{R_{m2}}+({\mathrm{\α}}_{31}T+{\mathrm{\α}}_{32}{T}^2+{\mathrm{\α}}_{33}{T}^3)\]---\left(14\right)$

Above formula shows, the temperature characterisitic of non-linear current only can be had an impact by the temperature characterisitic of memristor, without The temperature characterisitic of PTAT current and CTAT current is produced impact, and non-linear current is to temperature exponentially type Relation, its Monomial coefficient, quadratic term coefficient, cubic term coefficient compare the coefficient of the temperature characterisitic of memristor Bigger, therefore the impact of reference voltage can be ignored by the temperature characterisitic of memristor.

To sum up, a kind of temperature-compensation circuit for crystal oscillator of the present invention produces temperature is cube function Reference voltage V_ref, in control signal Cont_R_m1、Cont_R_m2、Cont_R_m3With under Cont_NL effect, Realize the size to output reference voltage, Monomial coefficient, quadratic term coefficient, the control of cubic term coefficient, Thus according to the characteristic using temperature-frequency of different crystal, change temperature coefficient and the zero-temperature coefficient system of reference voltage Several points.The capacitance of this reference voltage control varactor, thus the oscillation frequency of accurate compensated crystal oscillator The skew that rate produces because of variations in temperature, carries high-frequency temperature stability.

The invention have the benefit that the crystal to different temperatures characteristic, produce temperature coefficient and zero-temperature coefficient system The reference voltage that several points are different, motility is high, and compensation precision is high；Do not use the mode of segmented compensation, electricity Line structure is simple, low cost；Need not the regulation of RAM and PROM write parameters and compensate the coefficient of voltage, Need not single temperature sensor, it is not necessary to critesistor and fixed resistor network, it is easy to miniaturization and collection Cheng Hua.

Accompanying drawing explanation

Fig. 1 is the theory diagram that a kind of temperature-compensation circuit for crystal oscillator of the present invention works；

Fig. 2 is the circuit diagram of a kind of temperature-compensation circuit for crystal oscillator of the present invention；

Fig. 3 is in control signal Cont_R_m1R is changed under effect_m1To reference voltage temperature coefficient and low-temperature zone zero The simulation result of temperature coefficient point impact；

Fig. 4 is in control signal Cont_R_m2R is changed under effect_m2To reference voltage temperature coefficient and low-temperature zone zero The simulation result of temperature coefficient point impact；

Fig. 5 is that the control word changing control signal Cont_NL is to reference voltage temperature coefficient and high temperature section zero temperature The simulation result of coefficient point impact.

Detailed description of the invention

The tool of a kind of temperature-compensation circuit for crystal oscillator of the present invention is given below in conjunction with Fig. 1 and Fig. 2 Body embodiment.It should be noted that this embodiment is intended merely to explain the present invention, it is not to the present invention's Limit.

Fig. 1 is the principle frame that a kind of temperature-compensation circuit for crystal oscillator that the present embodiment provides works Figure, temperature-compensation circuit is in control signal Cont_R_m1、Cont_R_m2、Cont_R_m3With Cont_NL effect Under, produce size, Monomial coefficient, quadratic term coefficient and the adjustable reference voltage V of cubic term coefficient_ref, The capacitance of varactor in this voltage controlled crystal oscillator, thus the frequency of oscillation of compensated crystal oscillator Because the skew that variations in temperature produces.

Fig. 2 is the circuit structure of a kind of temperature-compensation circuit for crystal oscillator of the present embodiment, including starting Circuit, adjustable PTAT current source, adjustable CTAT current source, adjustable non-linear current source, electric current Summation module and adjustable current-voltage converter.

Start-up circuit includes p-type metal-oxide-semiconductor MS1, MS2 and electric capacity C1.The grid of MS1 meet V_A, miss The grid of MS2, source meets power supply VCC, and the grid of MS2 connect leakage and the anode of electric capacity C1 of MS1, and source connects power supply VCC, misses the grid of MN1, the grid just terminating MS2 of electric capacity C1, negativing ending grounding current potential.Start-up circuit For in power supply electrifying moment, provide the DC point of non-zero, circuit start to adjustable PTAT current source After completing, start-up circuit cuts out, and does not consume electric current.Power supply electrifying moment, MS2 opens, to the grid of MN1 Node input current, thus MN2 conducting, produce electric current, when adjustable PTAT current source has started, MS1 detects that the grid current potential of MP1 rises, and the grid current potential of MS2 can be made to increase, rise to after MS1 conducting When the gate source voltage of MS2 approximates the threshold voltage of MS2, MS2 closes, and startup completes, and hereafter starts electricity Road does not consume electric current, and adjustable PTAT current source will not be produced impact.

Adjustable PTAT current source includes 4 p-type metal-oxide-semiconductors, respectively MP1, MP2, MP3 and MP4,4 N-type metal-oxide-semiconductors, respectively MN1, MN2, MN3 and MN4 and memristor networking R_m1。 The form that the grid of MP1 and leakage connect with diode is connected together, and meets the source of MP3 and the grid of MP2, MP1 Source meet power supply VCC；The source of MP2 and memristor network R_m1One end be connected, miss the source of MP4；MP3 Being connected together with the grid of MP4, source is connected with the leakage of MP1 and MP2 respectively, leakage respectively with MN1 and MN2 Leakage be connected, the grid of MP3 the most also connect the leakage of MP3；The substrate of MP2 is connected with source and eliminates lining effect partially Should, the substrate of MP1, MP3, MP4 all meets power supply VCC；Memristor networking R_m1Another termination power VCC；N-type metal-oxide-semiconductor MN1, MN2, MN3 and MN4 constitute common-source common-gate current mirror, MN1's Missing the leakage of MP3, source connects the leakage of MN3, and grid connect grid and the leakage of MN2；The leakage missing MP4 of MN2, Source connects the leakage of MN4；The grid of MN3 with MN4 are connected, and connect the leakage of MN4, the source of MN3 and MN4 All earthing potentials；The substrate of MN1, MN2, MN3, MN4 all earthing potentials.

Further, p-type metal-oxide-semiconductor MP1, MP2 and memristor network R_m1Produce the electric current of positive temperature coefficient, I.e. PTAT current；P-type metal-oxide-semiconductor MP3 and MP4 forms current mirror, it is ensured that V_AAnd V_BEqual, improve The precision of PTAT current source；N-type metal-oxide-semiconductor MN1, MN2, MN3, MN4 composition cascade electricity Stream mirror loads, and bank tube MN1 and MN2 has been effectively isolated the fluctuation of supply voltage altogether, improves adjustable The PSRR of PTAT current source.

Further, described MP1 and MP2 is operated in subthreshold region, is used for producing PTAT voltage, its number Ratio is made up of the metal-oxide-semiconductor of 1 unit for 1:N, i.e. MP1, and MP2 is by the metal-oxide-semiconductor of N number of unit also Joint group becomes, then its breadth length ratio is: (W/L)_MP1:(W/L)_MP2=1:N (N >=2).Owing to MP1 and MP2 is by difference The metal-oxide-semiconductor composition of number same unit, its threshold voltage is identical.MN1 and MN2 and MN3 and MN4 Breadth length ratio be respectively as follows: (W/L)_MN1:(W/L)_MN2=1:1, (W/L)_MN3:(W/L)_MN4=1:1, it is ensured that MP1 and MP2 Electric current equal, and be all PTAT current.Utilize the index of the current-voltage of the MOS being operated in subthreshold region Relation and the annexation of circuit, this PTAT current is expressed as:

$I_{FTAT}=\frac{kT}{{\mathrm{qR}}_{m1}}lnN={\mathrm{\α}}_{11}T---\left(15\right)$

Wherein, α₁₁It it is the Monomial coefficient of PTAT current.

Adjustable PTAT current source produces the size PTAT current different with Monomial coefficient by the following method Realize: memristor network R_m1It is made up of m × n memristor, internal with erasable circuit, believed by control Number Cont_R_m1Control, it is achieved arbitrarily resistance, thus adjust the slope of PTAT current₁₁, change benchmark Voltage V_refTemperature coefficient and low-temperature zone zero temperature coefficient point.Fig. 3 is individually to change memristor network R_m1Resistance The value (± 5%) reference voltage V to output_refTemperature coefficient and low-temperature zone zero temperature coefficient point impact emulation knot Really, simulation result shows, Cont_R_m1Signal is to reference voltage V_refControl action obvious.

In reality, due to the non-ideal factor in semiconductor technology production process, the mismatch of metal-oxide-semiconductor can be caused. Consider that MP1 and MP2 does not mates and V_AAnd V_BThe unequal nonlinear characteristic caused, PTAT current represents For:

I_PTAT=α₁₁T+α₁₂T² (16)

Wherein, α₁₂Being the quadratic term coefficient of PTAT current, its value compares α₁₁Smaller.

Described adjustable CTAT current source include p-type metal-oxide-semiconductor MP5 and MP6, N-type metal-oxide-semiconductor MN5, MN6, MN7 and MN9, amplifier OPA and memristor network R_m2.The grid leak of MP5 is with diode It is connected together, and connects the in-phase input end of amplifier OPA, source and substrate and meet power supply VCC；The grid of MP6 connect fortune Putting the outfan of OPA, source connects the inverting input of amplifier OPA, and with memristor network R_m2One end phase Even；Memristor network R_m2The other end be connected with power supply VCC；MN5 and MN6 grid connect respectively MN2 and The grid of MN4, the source of MN5 connects the leakage of MN6, misses the leakage of MP5, the source earthing potential of MN6；MN7 Grid and the form that connects with diode of leakage be connected together, and connect the leakage of MP6, source connects the leakage of MN9；MN9 Grid leak connect together and be connected with the source of MN7, source earthing potential；MN5, MN6, MN7, MN9's Substrate all earthing potentials；MP5, amplifier OPA and memristor network R_m2Produce CTAT current, MN5 and MN6 composition current mirror mirror image PTAT current provides direct current biasing to MP5, MN7 and MN9 forms electric current Mirror does load and the output CTAT current of MP6.

Further, above-mentioned p-type metal-oxide-semiconductor MP5 is operated in subthreshold region, is used for producing CTAT voltage. For being operated in the metal-oxide-semiconductor of subthreshold region, when its electric current is fixed value, its gate source voltage V_sg5There is negative temperature Degree coefficient is generally-2mV/ DEG C～-1mV/ DEG C, the most relevant to the bias conditions of MP5.In this embodiment, MP5 PTAT current biases, and owing to PTAT current has less positive temperature coefficient, causes V_sg5Subzero temperature Coefficient ratio-2mV/ DEG C～-1mV/ DEG C is smaller.For preferable amplifier, its gain is infinitely great, by its " empty short " Characteristic is known, the current potential of in-phase input end and inverting input is equal, it may be assumed that

V_in+=V_in- (17)

Source and memristor network R due to MP5_m2One end all meet identical power supply VCC, therefore memristor net Network R_m2The voltage at two ends is V_sg5, so the electric current flowing through memristor network is V_sg5/R_m2.Due to V_sg5Have negative Temperature coefficient, ignores R_m2Temperature coefficient time, flow through memristor network R_m2Electric current also there is negative temperature system Number, is expressed as:

$I_{CTAT}=\frac{V_{sg5}}{R_{m2}}={\mathrm{\α}}_{21}T---\left(18\right)$

Wherein, α₂₁It it is the Monomial coefficient that varies with temperature of CTAT current.

Described adjustable CTAT current source produces the size CTAT current different with Monomial coefficient by following Method realizes: memristor network R_m2It is made up of m × n memristor, internal with erasable circuit, by control Signal Cont_R processed_m2Control, it is achieved arbitrarily resistance, thus adjust the slope of CTAT current₂₁, change Reference voltage V_refTemperature coefficient and low-temperature zone zero temperature coefficient point.Fig. 4 is individually to change memristor R_m2Resistance The value (± 5%) reference voltage V to output_refTemperature coefficient and low-temperature zone zero temperature coefficient point impact emulation knot Really, simulation result shows, Cont_R_m2Signal is to reference voltage V_refControl action obvious.

Consider V_sg5Due to the temperature characterisitic of bias current, cause non-linear such as amplifier OPA imbalance and self Non-linear, then CTAT current can be expressed as:

I_CTAT=α₂₁T+α₂₂T² (19)

Wherein, α₂₂Being the quadratic term coefficient that varies with temperature of CTAT current, its value compares α₂₁Smaller.

Adjustable non-linear current source includes k the N-type metal-oxide-semiconductor of M1～Mk, the k of SW1～SWk Individual selection switchs and decoder S composition.The grid end of k the N-type metal-oxide-semiconductor of M1～Mk divides with source The most connected, drain terminal one end with the switch of SW1～SWk respectively is connected, another termination of all switches together, Output signal Cont_1 of decoder S～Cont_k control the switch of SW1～SWk respectively, decoder Input connects control signal Cont_NL.

Further, k the N-type metal-oxide-semiconductor of M1～Mk is operated in sub-threshold region, and its electric current is non-linear Electric current, is expressed as:

$I_{Mk}={\mathrm{\μC}}_{ox}{\left(\frac{W}{L}\right)}_{Mk}(\mathrm{\η}-1){\left(\frac{kT}{q}\right)}^2\exp \left(\frac{-{\mathrm{qV}}_{th}}{\mathrm{\η}kT}\right)---\left(20\right)$

Wherein, I_MkBeing the electric current flowing through metal-oxide-semiconductor Mk, μ is carrier mobility, C_oxIt it is gate oxide list Position area capacitance, W is channel width, and L is channel length, and η is subthreshold obliquity factor, and q is electron charge, K is Boltzmann constant, and T is absolute temperature, V_thIt it is the threshold voltage of Mk.This electric current is the non-thread of temperature Property function, by this electric current Taylor series expansion to three rank items, ignores higher order term, then this non-linear current table It is shown as:

I_NL=α₃₁T+α₃₂T²+α₃₃T³ (21)

Wherein, α₃₁It is non-linear current I_NLThe Monomial coefficient varied with temperature, α₃₂It is non-linear current I_NLWith The quadratic term coefficient of variations in temperature, α₃₃It is non-linear current I_NLThe cubic term coefficient varied with temperature.

Further, in k the N-type metal-oxide-semiconductor of M1～Mk, M1 is made up of 1 unit, and M2 is by two Individual unit composes in parallel, and Mk is composed in parallel by k unit, and their breadth length ratio meets: (W/L)_M1:(W/L)_M2:...:(W/L)_Mk=1:2:...:k.It is all to be composed in parallel by identical unit due to M1～Mk, Its threshold voltage is identical, then the current ratio flowing through M1～Mk meets: I_M1:I_M2:...:I_Mk=1:2:...:k.

Described non-linear current source produces size, Monomial coefficient, quadratic term coefficient and cubic term coefficient respectively can The non-linear current adjusted is accomplished by: under different control word Cont_NL effects, decoder Output signal Cont_1 of S～Cont_k only one of which signal at any time is effective, thus switch SW1～ SWk only one of which at any time is opened, so this moment only has a metal-oxide-semiconductor in M1～Mk Non-linear current can export.Change the control word of input signal Cont_NL of decoder S, then can change Become control signal Cont_1～the effectiveness of Cont_k of switch, thus change the big of the non-linear current of output Little and temperature coefficient.Fig. 5 is the control word individually the changing control signal Cont_NL reference voltage to output V_refTemperature coefficient and high temperature section zero temperature coefficient point impact simulation result, simulation result shows, Cont_NL Signal is to reference voltage V_refControl action obvious.

Electric current summation module includes N-type metal-oxide-semiconductor MN8, MN10, MN11 and MN12.MN8's Grid connect the grid of MN7, and source connects the leakage of MN10, miss the leakage of MN11；The grid of MN10 connect the grid of MN9, Source earthing potential；MN9 and MN10 forms current mirror mirror image CTAT current.In like manner, MN11 and MN12 Composition current mirror mirror image PTAT current, the grid of MN11 connect the grid of MN2, and source meets the leakage of MN12, MN12 Grid connect the grid of MN4, miss the leakage of MN8, source earthing potential；MN8、MN10、MN11、MN12 Substrate all earthing potentials；The leakage of MN8 simultaneously is connected with the leakage of MN11, and connects adjustable non-linear current The other end of source breaker in middle, forms reference current, and this electric current can be expressed as:

I_ref=I_PTAT+I_CTAT+I_NL=(α₁₁+α₂₁+α₃₁)T+(α₁₂+α₂₂+α₃₂)T²+α₃₃T³ (22)

Adjustable current-voltage converter includes the memristor network R of m × n memristor composition_m3.Memristor net Network R_m3A termination power VCC, another termination MN8 leakage, be also the outfan of reference voltage.This base Quasi-voltmeter is shown as:

V_ref=V_DD-R_m3[(α₁₁+α₂₁+α₃₁)T+(α₁₂+α₂₂+α₃₂)T²+α₃₃T³] (23)

Due to memristor network R_m3Internal with erasable circuit, by control signal Cont_R_m3Control, real Incumbent meaning resistance, thus according to the characteristic of varactor, the size of regulation reference voltage.This reference voltage It is cube functional relationship to temperature, is regulated the coefficient of each item of this reference voltage by control signal, it is achieved The migration produced the frequency of oscillation of crystal because of variations in temperature, improves the temperature stability of crystal oscillating circuit.

The temperature characterisitic of said reference voltage does not accounts for the temperature characterisitic of memristor network, in reality, memristor Network has temperature characterisitic, it is contemplated that after the temperature characterisitic of memristor network, and benchmark can be expressed as:

$V_{ref}=V_{DD}-R_{m3}\left(T\right)\[\frac{{\mathrm{\ΔV}}_{gs}}{R_{m1}\left(T\right)}+\frac{V_{sg5}}{R_{m2}\left(T\right)}+({\mathrm{\α}}_{31}T+{\mathrm{\α}}_{32}{T}^2+{\mathrm{\α}}_{33}{T}^3)\]---\left(24\right)$

Above formula shows, the temperature characterisitic of non-linear current only can be had an impact, but by the temperature characterisitic of memristor network The temperature characterisitic of PTAT current and CTAT current will not be produced impact, and non-linear current is finger to temperature Number type relation, its Monomial coefficient, quadratic term coefficient, cubic term coefficient compare the temperature characterisitic of memristor Coefficients comparison is big, therefore the impact of reference voltage can be ignored by the temperature characterisitic of memristor.

Fig. 3, Fig. 4 and Fig. 5 show, control signal Cont_R_m1、Cont_R_m2, Cont_NL to output Reference voltage V_refTemperature coefficient and the regulation effect of high/low temperature zero temperature coefficient point obvious, thus according to difference The frequency-temperature characteristic of crystal regulates the temperature characterisitic of this reference voltage, and control mode is simple, it is not necessary to by ginseng The mode of number write RAM and PROM regulates the temperature coefficient of reference voltage, provides cost savings.

Claims (6)

1. for the temperature-compensation circuit of crystal oscillator, including start-up circuit, adjustable PTAT current source, adjustable CTAT current source, adjustable non-linear current source, electric current summation module and adjustable current-voltage converter, its feature exists In:

Described start-up circuit includes p-type metal-oxide-semiconductor MS1, MS2 and electric capacity C1；For in power supply electrifying moment, to adjustable PTAT current source provide non-zero DC point, after circuit start completes, start-up circuit close, do not consume electric current；

The grid of MS1 meet V_A, miss the grid of MS2, source meets power supply VCC, and the grid of MS2 are just meeting the leakage of MS1 and electric capacity C1 End, source meets power supply VCC, misses the grid of MN1, the negativing ending grounding current potential of electric capacity C1；

Described adjustable PTAT current source includes 4 p-type metal-oxide-semiconductors, respectively MP1, MP2, MP3 and MP4,4 Individual N-type metal-oxide-semiconductor, respectively MN1, MN2, MN3 and MN4 and the memristor network R of m × n memristor composition_m1, M ＞ 1, n ＞ 1；R_m1Internal with erasable circuit, by control signal Cont_R_m1Realize any resistance, produce size and The PTAT current that secondary term coefficient is different；

The source of MP1 connects power supply VCC, grid and leakage and is connected together with the form of diode connection, and meets source and the MP2 of MP3 Grid；The source of MP2 and memristor network R_m1One end be connected, miss the source of MP4；The grid of MP3 and MP4 are connected together, Leakage is connected with the leakage of MN1 and MN2 respectively, and the grid of MP3 the most also connect the leakage of MP3；The substrate of MP2 is connected with source and disappears Except body bias effect, the substrate of MP1, MP3 and MP4 all meets power supply VCC；Memristor network R_m1Another termination power VCC；The leakage missing MP3 of MN1, source connects the leakage of MN3, and grid connect grid and the leakage of MN2；MN2 misses MP4's Leakage, source connects the leakage of MN4；The grid of MN3 with MN4 are connected, and connect the leakage of MN4, the source of MN3 and MN4 all ground connection electricity Position；The substrate of MN1, MN2, MN3 and MN4 all earthing potentials；

Described adjustable CTAT current source include p-type metal-oxide-semiconductor MP5 and MP6, N-type metal-oxide-semiconductor MN5, MN6, MN7 and MN9, amplifier OPA and the memristor network R of m × n memristor composition_m2, m ＞ 1, n ＞ 1；R_m2Internal band There is erasable circuit, by control signal Cont_R_m2Realize any resistance, produce the CTAT electricity that size is different with Monomial coefficient Stream；

The grid leak of MP5 is connected together with diode, and connects the in-phase input end of amplifier OPA, source and substrate and meet power supply VCC； The grid of MP6 connect the outfan of amplifier OPA, and source connects the inverting input of amplifier OPA, and with memristor network R_m2One end phase Even；Memristor network R_m2The other end be connected with power supply VCC；MN5 and MN6 grid connect the grid of MN2 and MN4 respectively, The source of MN5 connects the leakage of MN6, misses the leakage of MP5, the source earthing potential of MN6；The grid of MN7 and leakage connect with diode Form be connected together, and connect the leakage of MP6, source connects the leakage of MN9；The grid leak of MN9 connects together and is connected with the source of MN7, Source earthing potential；The substrate of MN5, MN6, MN7 and MN9 all earthing potentials；

Described adjustable non-linear current source is by k the N-type metal-oxide-semiconductor of M1～Mk, k the selection switch of SW1～SWk And decoder S composition；Size, Monomial coefficient, quadratic term coefficient, cubic term coefficient is produced equal under Cont_NL control Different non-linear currents；

The grid end of k the N-type metal-oxide-semiconductor of M1～Mk is respectively connected with respective source, and drain terminal is respectively with SW1's～SWk The one end selecting switch is connected, and substrate is all connected with earth potential；The other end of k the selection switch of SW1～SWk is connected together And be connected with the leakage of MN8；Output signal Cont_1 of decoder S～Cont_k control the switch of SW1～SWk respectively, translate The input of code device connects control signal Cont_NL；

Described electric current summation module includes N-type metal-oxide-semiconductor MN8, MN10, MN11 and MN12；To described PTAT electricity Stream, CTAT current and non-linear current modulus, generation is the electric current of cube function to temperature；

MN7, MN8, MN9 and MN10 form common-source common-gate current mirror mirror image CTAT current, and the grid of MN8 meet MN7 Grid, source connects the leakage of MN10, misses the leakage of MN11；The grid of MN10 connect the grid of MN9, source earthing potential；In like manner, MN2, MN4, MN11 and MN12 form common-source common-gate current mirror mirror image PTAT current, and the grid of MN11 connect the grid of MN2, Source connects the leakage of MN12, and the grid of MN12 connect the grid of MN4, misses the source of MN11, source earthing potential；MN8、MN10、 The substrate of MN11 and MN12 all earthing potentials, the leakage of MN8 simultaneously is connected with the leakage of MN11, and connects the defeated of non-linear current Go out end, form reference current I_ref；

Described adjustable current-voltage converter includes the memristor network R of m × n memristor composition_m3, memristor network R_m3's One termination power VCC, the leakage of another termination MN8；Converting electrical current into voltage, this voltage versus temperature is cube functional relationships System, for controlling the capacitance of varactor in crystal oscillator, compensates the skew that the frequency of oscillation of crystal produces because of variations in temperature； Memristor network R_m3Internal with erasable circuit, by control signal Cont_R_m3Control, it is achieved arbitrarily resistance, thus root According to the characteristic of varactor, regulate reference voltage V_refSize.

A kind of temperature-compensation circuit for crystal oscillator, it is characterised in that: described MP1 and MP2 is operated in subthreshold region, and its number is made up of the metal-oxide-semiconductor of 1 unit than for 1:N, i.e. MP1, and MP2 is by N number of list The metal-oxide-semiconductor of unit composes in parallel, then its breadth length ratio is: (W/L)_MP1:(W/L)_MP2=1:N (N >=2)；Flow through MP1's and MP2 Electric current is equal, and is all PTAT current, is expressed as:

I_PTAT=α₁₂T+α₁₂T² (6)

Wherein, I_PTATIt is PTAT current, α₁₁It is the Monomial coefficient of PTAT current, α₁₂It it is the secondary term system of PTAT current Number.

A kind of temperature-compensation circuit for crystal oscillator, it is characterised in that: described p-type MOS Pipe MP5 is operated in subthreshold region, is used for producing CTAT voltage, and this voltage drop is at memristor network R_m2Two ends produce CTAT electricity Stream, particularly as follows:

I_CTAT=α₂₁T+α₂₂T² (7)

Wherein, I_CTATIt is CTAT current, α₂₁It is the Monomial coefficient that varies with temperature of CTAT current, α₂₂It it is CTAT current The quadratic term coefficient varied with temperature.

A kind of temperature-compensation circuit for crystal oscillator, it is characterised in that: described M1～Mk K N-type metal-oxide-semiconductor be operated in sub-threshold region, its electric current is non-linear current, particularly as follows:

I_Mk=α₃₁T+α₃₂T²+α₃₃T³ (9)

Wherein, I_MkIt is the electric current flowing through metal-oxide-semiconductor Mk, α₃₁It is non-linear current I_MkThe Monomial coefficient varied with temperature, α₃₂ It is non-linear current I_MkThe quadratic term coefficient varied with temperature, α₃₃It is non-linear current I_MkThe cubic term coefficient varied with temperature.

A kind of temperature-compensation circuit for crystal oscillator, it is characterised in that: described decoder S Output signal Cont_1～Cont_k only one of which signal at any time effective, thus switch SW1～SWk when any Quarter, only one of which was opened, so this moment only has a metal-oxide-semiconductor electric current in M1～Mk to export, formed non-linear electricity Stream, it may be assumed that

I_NL=α₃₁T+α₃₂T²+α₃₃T³ (11)。

A kind of temperature-compensation circuit for crystal oscillator, it is characterised in that: final output reference Voltage V_refFor:

V_ref=V_DD-R_m3[(α₁₁+α₂₁+α₃₁)T+(α₁₂+α₂₂+α₃₂)T²+α₃₃T³] (13)。