CN101620450A - High-precision constant flow source circuit - Google Patents

Abstract

The invention discloses a high-precision constant flow source circuit which consists of two parts of a PTAT current generation circuit and a core circuit, wherein the PTAT current generation circuit generates a PTAT current with a certain negative temperature coefficient for the core circuit based on a principle of a BANGAP circuit. The core circuit mainly comprises a control MOS pipe, a positive temperature coefficient resistor and a current mirror image circuit and obtains a high-precision and low temperature coefficient constant current through a certain control relation by utilizing the PTAT current provided by a pre-stage circuit. The invention has the advantages of providing the high-precision and low temperature coefficient constant current for a relevant application occasion, and not only improves the overall performance of the application circuit, but also simplifies a peripheral circuit and reduces the application cost compared with a conventional method. The invention adopts a CMOS process, has good processing compatibility, saves the cost and better meets the requirement of the industrialization production of integrated circuits.

Description

High-precision constant flow source circuit

Technical field

The present invention relates to constant-current source circuit, belong to field of analog integrated circuit.Be particularly related to a kind of high-precision constant flow source circuit that produces electric current based on the CMOS processing procedure with very high linear adjustment capability and good temperature characterisitic.

Background technology

High precision, low temperature coefficient constant current are widely used in circuit such as clock control, oscillator.According to classic method, this electric current is to be realized divided by non-essential resistance by internal reference voltage, as adopting current regulator diode or realizing that with the triode of two homotypes the current precision of right this mode is low, and again owing to being to adopt discrete electronic component to realize, so increased application cost in chip exterior.If can realize this electric current, will significantly improve the performance of integrated circuit and simplify the peripheral applications circuit at chip internal.

Summary of the invention

In view of this, the invention provides a kind of constant-current source circuit based on the CMOS processing procedure, this circuit can be under broad supply voltage operate as normal, produce a high-precision steady current, this electric current has very high linear adjustment capability and good temperature characterisitic, under the normal condition, temperature coefficient can reach 125ppm/ ℃.

For achieving the above object, the present invention proposes a kind of high-precision constant flow source circuit, and it comprises PTAT current generating circuit and core circuit, and this PTAT current generating circuit produces the PTAT electric current with negative temperature coefficient and uses for core circuit; Described core circuit comprises control metal-oxide-semiconductor M1, M2, resistance R s and current mirror circuit are by regulating the breadth length ratio of described metal-oxide-semiconductor M1, M2, the ratio of the breadth length ratio of metal-oxide-semiconductor M1, M2 and resistance sizes, reach the Positive and Negative Coefficient Temperature balance, make output current have very little temperature coefficient.

Described PTAT electric current produces and comprises bipolar transistor Q1, Q2, resistance R 1 and the current mirror circuit of being made up of metal-oxide-semiconductor M11～M18.

The current mirror circuit of described core circuit has imports described control metal-oxide-semiconductor M1, the electric current I 1 of M2, I2 and output current Iout respectively.

Described control metal-oxide-semiconductor M1, M2 is operated in the saturation region.

Make described current mirror circuit I1=I2=I, the breadth length ratio of this electric current I and metal-oxide-semiconductor M1, M2 then, the expression formula between the ratio of the breadth length ratio of metal-oxide-semiconductor M1, M2 and resistance R 1, Rs is:

$\sqrt{I}=A1+\sqrt{\frac{(I+A2)}{K}}$

Wherein

$A1=\frac{k{R}_{\mathrm{<figure-callout\; id="1"\; label="S\; q\; R"\; filenames="A2009101627240010H1.png"\; state="\{\{state\}\}">S</figure-callout>}}}{q{R}_{}}\ln N\&CenterDot;\frac{\sqrt{C_{\mathrm{OX}}(W/L)}}{\sqrt{2}}\&CenterDot;{{\mathrm{\&mu;}}_0}^{1/2}{T_0}^{3/4}\&CenterDot;{\mathrm{<figure-callout\; id="1"\; label="T"\; filenames="A2009101627240010H1.png"\; state="\{\{state\}\}">T</figure-callout>}}^{1/4}$

$A2=\frac{k}{q{R}_1[1+t{c}_1(T-T_0)+t{c}_2{(T-T_0)}^2]}\ln N\&CenterDot;T$

In the following formula, K is the scale-up factor between the breadth length ratio W/L of control metal-oxide-semiconductor M1, M2; μ ₀Be t=T ₀Electron mobility during=300K, tc1, tc2 are the temperature coefficient of resistance R 1, Rs, and k is a Boltzmann constant, and q is the quantity of electric charge, and Cox is the unit area gate oxide electric capacity of metal-oxide-semiconductor.

The current mirror circuit of described core circuit is made up of metal-oxide-semiconductor M3～M10.

The present invention is with reference to the design philosophy of constant pressure source, and the method that adopts the amount of two opposite temperature coefficients to compensate mutually obtains the magnitude of current of low-temperature coefficient.In the design of constant pressure source, because just in time there is the voltage that two temperatures coefficient are opposite and temperature curve is relatively more linear, thus can design the pretty good voltage source of performance at an easy rate, but in the current source design, there are not two such magnitudes of current, so the design of constant current source is a difficult point always.The present invention has adopted a circuit more cleverly, the negative temperature coefficient and the positive temperature coefficient of resistance of electron mobility have been utilized indirectly, breadth length ratio by regulating metal-oxide-semiconductor, metal-oxide-semiconductor are to ratio, these three parameters that ratio is easier to regulate of resistance sizes of breadth length ratio, reach the Positive and Negative Coefficient Temperature balance, thereby obtained the very constant magnitude of current of temperature coefficient, this invention is simple in structure, and insensitive to process deviation, area occupied is few.

Description of drawings

Fig. 1 is a high-precision constant flow source circuit principle schematic of the present invention;

Fig. 2 is high-precision constant flow source circuit figure of the present invention.

Embodiment

As Fig. 1,2 show, disclosed high-precision constant flow source circuit comprises PTAT (ProportionalTo Absolute Temperature, proportional with absolute temperature) current generating circuit and core circuit, wherein the PTAT current generating circuit principle that is based on BANDGAP (band-gap reference) circuit generates the PTAT electric current with negative temperature coefficient and uses for core circuit, it is by bipolar transistor Q1, Q2, and metal-oxide-semiconductor M11～M18 and resistance R 1 are formed.The electric current I that this circuit produces _PTATCan be expressed as:

$I_{\mathrm{PTAT}}=\frac{V_T\&CenterDot;\mathrm{LnN}}{{\mathrm{<figure-callout\; id="1"\; label="R"\; filenames="A2009101627240010H1.png"\; state="\{\{state\}\}">R</figure-callout>}}_1}$

V wherein _TBe thermoelectrical potential, N is the ratio of the area of two bipolar transistor Q2 and Q1, and R1 is the resistance with positive temperature coefficient (PTC).In general processing procedure, temperature-coefficient of electrical resistance is greater than the temperature coefficient of thermal voltage, thereby makes I _PTATPresent negative temperature characteristic.

Core circuit is mainly by control metal-oxide-semiconductor M1, M2, the resistance R s and the current mirror circuit that have temperature coefficient of the same type with resistance R 1 are formed, in the present embodiment, current mirror circuit is made up of metal-oxide-semiconductor M3～M10, the effect of current mirror circuit M3～M8 is to force M1, M2 to have identical electric current I 1=I2=I, and I is by current mirror circuit M9, M10 output current Iout.The breadth length ratio of control metal-oxide-semiconductor M1, M2 is respectively W/L and K (W/L), and all is operated in the saturation region; Can draw following relation according to I1=I2=I:

$\sqrt{\frac{2I}{{\mathrm{\&mu;}}_n{C}_{\mathrm{OX}}(W/L)}}+{\mathrm{<figure-callout\; id="1"\; label="V\; TH"\; filenames="A2009101627240010H1.png"\; state="\{\{state\}\}">V</figure-callout>}}_{\mathrm{TH}}=\sqrt{\frac{2(I+I_{\mathrm{PTAT}})}{{\mathrm{\&mu;}}_n{C}_{\mathrm{OX}}K(W/L)}}+V_{\mathrm{TH}2}+I_{\mathrm{PTAT}}\&CenterDot;R_S---\left(1\right)$

V wherein _TH1And V _TH2Be respectively the threshold voltage of control metal-oxide-semiconductor M1, M2, and its approximately equal, so formula (1) can be reduced to:

$\sqrt{I}-\sqrt{\frac{(I+I_{\mathrm{PTAT}})}{K}}=I_{\mathrm{PTAT}}\&CenterDot;R_S\frac{\sqrt{{\mathrm{\&mu;}}_n}\&CenterDot;\sqrt{C_{\mathrm{OX}}(W/L)}}{\sqrt{2}}---\left(2\right)$

With the electron mobility model ${\mathrm{\&mu;}}_n={\mathrm{\&mu;}}_0{\left(\frac{T}{T_0}\right)}^{-3/2}$ And V _T=kT/q substitution formula (2), abbreviation gets:

$\sqrt{I}=\frac{k{R}_{\mathrm{<figure-callout\; id="1"\; label="S\; q\; R"\; filenames="A2009101627240010H1.png"\; state="\{\{state\}\}">S</figure-callout>}}}{q{R}_{}}\ln N\&CenterDot;\frac{\sqrt{C_{\mathrm{OX}}(W/L)}}{\sqrt{2}}\&CenterDot;{{\mathrm{\&mu;}}_0}^{1/2}{T_0}^{3/4}\&CenterDot;{\mathrm{<figure-callout\; id="1"\; label="T"\; filenames="A2009101627240010H1.png"\; state="\{\{state\}\}">T</figure-callout>}}^{1/4}+\sqrt{\frac{(I+\frac{k}{q{R}_1[1+t{c}_1(T-T_0)+t{c}_2{(T-T_0)}^2]}\ln N\&CenterDot;T)}{K}}---\left(3\right)$

In the following formula, μ ₀Be t=T ₀Electron mobility during=300K, tc1, tc2 are the temperature coefficient of resistance R 1, Rs, and k is a Boltzmann constant, and q is the unit charge amount, and Cox is the unit area gate oxide electric capacity of metal-oxide-semiconductor.

Can find that from formula (3) I is T, K, the isoparametric implicit function of W/L, the analytical expression of directly deriving I is relatively more difficult.Be easy analysis, order:

$A1=\frac{k{R}_{\mathrm{<figure-callout\; id="1"\; label="S\; q\; R"\; filenames="A2009101627240010H1.png"\; state="\{\{state\}\}">S</figure-callout>}}}{q{R}_{}}\ln N\&CenterDot;\frac{\sqrt{C_{\mathrm{OX}}(W/L)}}{\sqrt{2}}\&CenterDot;{{\mathrm{\&mu;}}_0}^{1/2}{T_0}^{3/4}\&CenterDot;{\mathrm{<figure-callout\; id="1"\; label="T"\; filenames="A2009101627240010H1.png"\; state="\{\{state\}\}">T</figure-callout>}}^{1/4}$

$A2=\frac{k}{q{R}_1[1+t{c}_1(T-T_0)+t{c}_2{(T-T_0)}^2]}\ln N\&CenterDot;T$

Thus, formula (3) can be expressed as:

$\sqrt{I}=A1+\sqrt{\frac{(I+A2)}{K}}---\left(4\right)$

By the expression formula of A1 and A2 as can be known, A1 has less positive temperature coefficient (PTC) and (is about T ^1/4, according to the actual process condition, this value may have deviation slightly), A2 has less negative temperature coefficient (this temperature coefficient is mainly determined by the temperature coefficient of resistance).The temperature coefficient that makes I is zero, exists the value of one group of A1, A2 and K to make equation (4) set up under temperature variation in theory.Need to prove that W/L only influences A1 in the practical adjustments process, K only influences A2, and Rs/R1 influences A1, and W/L, K, Rs/R1 do not have temperature coefficient, can adjust the result by this thinking.In the example test, the current offset overwhelming majority is in 2% in-40 ℃ to the 120 ℃ scopes.What be worth proposition is that A1, A2 just have very weak temperature coefficient, in case the temperature coefficient of I is adjusted to acceptable scope, change W/L slightly again, K, parameters such as Rs/R1 can not have tangible influence to temperature coefficient, but can change the absolute value of I, this makes the industry personnel can obtain a good exercisable Trim mode thus, thereby can Trim Rs reaches the effect of Trim electric current.

Technology contents of the present invention and technical characterictic have disclosed as above; yet those of ordinary skill in the art still may be based on teaching of the present invention and announcements and are done all replacement and modifications that does not deviate from spirit of the present invention; therefore; protection domain of the present invention should be not limited to the content that embodiment discloses; and should comprise various do not deviate from replacement of the present invention and modifications, and contained by the present patent application claim.

Claims (6)

1. high-precision constant flow source circuit, it comprises PTAT current generating circuit and core circuit, this PTAT current generating circuit produces the PTAT electric current with negative temperature coefficient and uses for core circuit; It is characterized in that: described core circuit comprises control metal-oxide-semiconductor M1, M2, resistance R s and current mirror circuit; By regulating the breadth length ratio of described metal-oxide-semiconductor M1, M2, the ratio of the breadth length ratio of metal-oxide-semiconductor M1, M2 and resistance sizes reach the Positive and Negative Coefficient Temperature balance, make output current have very little temperature coefficient.

2. high-precision constant flow source circuit as claimed in claim 1 is characterized in that: described PTAT electric current produces and comprises bipolar transistor Q1, Q2, resistance R 1 and the current mirror circuit of being made up of metal-oxide-semiconductor M11～M18.

3. high-precision constant flow source circuit as claimed in claim 1 is characterized in that: the current mirror circuit of described core circuit has imports described control metal-oxide-semiconductor M1, the electric current I 1 of M2, I2 and output current Iout respectively.

4. high-precision constant flow source circuit as claimed in claim 3 is characterized in that: described control metal-oxide-semiconductor M1, M2 is operated in the saturation region.

5. high-precision constant flow source circuit as claimed in claim 3, it is characterized in that: make described current mirror circuit I1=I2=I, the breadth length ratio of this electric current I and metal-oxide-semiconductor M1, M2 then, the expression formula between the ratio of the breadth length ratio of metal-oxide-semiconductor M1, M2 and resistance R 1, Rs is:

$\sqrt{I}=A1+\sqrt{\frac{I+A2}{K}}$

Wherein

$A1=\frac{{\mathrm{kR}}_S}{{\mathrm{qR}}_1}\ln N\&CenterDot;\frac{\sqrt{C_{\mathrm{OX}}(W/L)}}{\sqrt{2}}\&CenterDot;{{\mathrm{\&mu;}}_0}^{1/2}{T_0}^{3/4}\&CenterDot;T^{1/4}$

$A2=\frac{k}{{\mathrm{qR}}_1[1+{\mathrm{tc}}_1(T-T_0)+{\mathrm{tc}}_2{(T-T_0)}^2]}\ln N\&CenterDot;T$

In the following formula, K is the scale-up factor between the breadth length ratio W/L of control metal-oxide-semiconductor M1, M2; μ ₀Be t=T ₀Electron mobility during=300K, tc1, tc2 are the temperature coefficient of resistance R 1, Rs, and k is a Boltzmann constant, and q is the unit charge amount, and Cox is the unit area gate oxide electric capacity of metal-oxide-semiconductor.

6. high-precision constant flow source circuit as claimed in claim 1 is characterized in that: the current mirror circuit of described core circuit is made up of metal-oxide-semiconductor M3～M10.

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