DE2938849A1 - TEMPERATURE COMPENSATED IC REFERENCE VOLTAGE - Google Patents

Description

The invention relates to a temperature compensated IC diffraction voltage according to the generic term of the main claim, i.e., on a diffraction stress for a solid-state building block. in the In particular, this invention relates to an improved arrangement or method for temperature compensation this reference voltage as well as a simplified procedure by which this reference voltage can be set so that it experiences an optimal compensation.

Diffraction voltages for solid-state building blocks usually have a voltage source consisting of semiconductor layers, for example a zener diode, but which has a significant temperature coefficient that makes compensation necessary. For many voltage reference devices, the voltage vs temperature relationship can be given by the following equation:

^V dev = V _{K +} ö6 (T - T _K ) (1)

where V \ j = the device terminal voltage at any temperature T, V _K and T "is constant and O ^ = a coefficient which varies with treatment of the device.

In order to provide compensation for the voltage changes occurring with temperature changes, the output signal of such a device can be superimposed with the voltage of a compensation spam circuit, this circuit, for example "band-gap junction ¹¹ source, having a temperature coefficient that is opposite to that

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Original is opposite in terms of sign (inclination), has a suitable scale of change to a specific one To generate output voltage levels. The characteristics of such a compensated reference voltage device can be given by the following equation:

/ T (V ₀₀ - β τ) στ + v _K + OC (τ -t _k ) J7 (2)

VIV

ref
where V_ _o = the "band-gap" voltage

the temperature coefficient of a forward biased pn junction,

CT "= a proportionality factor between the

Reference voltage device and the compensation device, and

an overall scale factor needed to obtain a specific voltage value.

Such a device has two degrees of freedom for the purpose of adjustment, symbolically represented by the characters ςρ (slope, slope) and () (scale) in equation (2) above. One principle for setting the device to specified operating characteristics is to use a computer-treated algorithm so as to set the CT value to an appropriate value so as to minimize the temperature-induced changes for a calculated value of 100 and um then adjust the value of ^ in order to obtain the specific output voltage ^v _re f · n. Obviously, this method requires two separate adjustment ^{steps, to be precise}

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Jewells one for each of the two degrees of freedom of the control circuit Draft. However, experience has shown that the aforementioned method is undesirably complex and expensive to carry out so that while it is commercially viable, it is not yet fully in effecting the desired compensation satisfied.

The invention is therefore based on the object of performing the compensation in such a way that the aforementioned disadvantages no longer occur appear.

This problem is solved according to the features of the characterizing part of the main claim

In accordance with an important aspect of the present invention, it has been found that highly satisfactory results can advantageously be obtained by a technique in which the reference voltage is set by a single element of the circuit while simultaneously controlling the two variable factors (given by fo and (j ~ in equation (2)), these factors controlling the output voltage and the temperature characteristics of the reference voltage. which brings the reference output voltage to the specific value, and which at the same time changes the temperature compensation control circuit so as to provide an optimal temperature compensation at the point at which the output reference voltage is equal to the specific value.

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In other words, it has been found that the two degrees of freedom that have hitherto been used for this purpose are complete Make adjustment of their reference voltage, can be reduced to a single degree of freedom so as to benefit the Quality of the reference voltage and at the same time to simplify the implementation procedure. The reduction of the setting procedure to a single degree of freedom can be understood in the mathematical sense that the variable Jl, of the size (J " was made dependent, namely by the topology of the assigned control circuit for the compensation voltage source. These Dependency relationship can be expressed as follows:

^v k

where V _ft = the specific output voltage. The output voltage can then be expressed as follows:

^ r ef '
^V ref ⁼ / ~ (V _rn -AT) (T + V _K

^V K (Γ ^V G0 ^ ¹ K

This gives the final expression:

+ V _K - oC T _K + (OC - / 6 CT ) T

V + ν »iki Φ

where Q "= the remaining setting parameter.

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In accordance with an important aspect of the invention, setting the value of V- makes it the specified value

λ re ι

(oC - / 5 (T *) to zero, i.e. by adding

β (Γ 'Ch sets, the desired equality is achieved within the limits of the model.

Further design features and further advantages of the invention emerge from the description of the exemplary embodiments shown in the drawing.

Show it:

1 shows a simplified circuit diagram to show the basic arrangement a preferred embodiment of the invention,

FIG. 2 is a circuit diagram showing details of tensile stress based on that shown in FIG. 1 Circuit, and

Fig. 3 is a diagram showing the voltage-temperature dependency different classes of voltage sources.

In Fig. 1, in accordance with the principles of this invention, the reference voltage comprises a zener diode voltage source 10 with one electrode of the diode connected to the output line 12 of an operational amplifier Ik . The other electrode of the diode is connected to the inverting input terminal 16 of the amplifier via a negative feedback circuit, this terminal in turn being connected via a resistor 18 to a common connecting line or to ground 20.

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The Zener diode 10 is designed as part of an IC chip, together with the associated control circuit according to FIG. 2. The chip also has the other circuits, not shown, which require the stabilized reference voltage to be generated, as will be explained later. The Zener diode is preferably designed as a "burled layer" device, for example as described in US application Ser.-No. 801, ¹ IlO of May 27, 1977 of the present applicant is executed.

The potential of the non-inverting terminal 22 of the amplifier 14 is held by a control circuit generally designated 24, this control circuit containing a second voltage source arrangement. This control circuit has two series-connected, mutually balanced transistors Q ₁ and Q ₂ , each of which has an emitter resistor R ₁ and R, respectively. The collector of the transistor Q ₂ is connected to the output line 12, while the emitter resistor R _{1 is connected} to ground. Furthermore, a voltage divider consisting of three resistors 26, 28, 30 is provided in order to keep the base voltages of the transistors Q ₁ , Q ₂ at predetermined levels, as will be explained below. The feedback circuit of the operational amplifier 14 keeps the input terminals 16 and 22 at the same potential so that the amplifier output voltage V can be regarded as the sum of the diode voltage V_ and the voltage applied to the non-inverting input 22. It should be noted that in the particular bridge-type circuit shown here, the voltage at the input or terminal 22 is also dependent on the output voltage V. However, this dependency is not a requirement of the present invention and other types of circuitry can be used to combine the Zener voltage with a compensation voltage.

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- ίο -

We Aue output voltage V can be represented as a function of circuit element values, and significant parameters, as will be discussed hereinafter. A detailed derivation of the relationships is given in the appendix at the end of the description. As shown in this derivative, the output voltage can be expressed by:

^V z ⁺ <ίς - *) ^V be

-6 ♦ «2

^R l

where V s is the zener diode voltage

V _be = the base-emitter voltage (from Q ₁ or Q ₂ )

ζ = the proportionality factor for the base voltage of Q ₂ (i.e. V _b2 - ^ V _Q ),

a is the proportionality factor for the base voltage of Q ₁ , and
R ₁ and R ₂ = the resistance values.

To determine a set of relationships for zero temperature compensation, one can use the derivative of equation (IA) with respect to temperature are formed and set to zero in order to specify the relationship:

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29388 ^ 9

^R 2 -. £ ^ (2A)

where / s is defined as the expression §φ \ ₆ , which is approximately equal to the value (V _Q0 - V _beQ ) / T ₀ ;

and where

s, as previously described, is equal to the value V ₇ ;

and
= is the "band-gap" voltage.

To the further necessary content for the conditions of the state To develop zero temperature compensation, equation IA can therefore be written as:

R ₂

1 -

where V _K and T _{R are constants slnd} (see equation (1 above)) and where T is the temperature of the device.

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Using equation (2A), the equation can be written as follows:

yjoo )

v _K + OO (Zoo - t _k )
¹ ^

where V _K , T _K , £> £ and fi are constants.

By taking the derivative of equation (4A) with respect to dt / and sets this equal to zero, one obtains the relationship:

ZK. £. (5A)

K ^ ¹ Yi 1 - f + 6

When this relationship is established, V _{Q is} independent of ch . This means that the control circuit can then deliver the desired result regardless of the specific Zener diode with which it is used.

Since the given parameters must be valid for some value of <? C /, another relationship for <f and £ can be found by putting & - 0 in equation (4a). This results in the expression:

^V K = l - S + £ (6a)

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for "λ The equations (5A) and (6A) can then be solved for / 6 and O , which results in:

£ ^s < ^V Q0 - ^ ^T K> ^{/ V}

QO "° ¹ K" ^¥ o (7A)

^{1 + fc} - ^Vr (8A)

The aforementioned relationships were derived to provide zero temperature compensation the specified output voltage. However, it can be modified by the same technique Relationships are derived for other types of desired control of the temperature coefficient, depending on the setting the output voltage to a specific value. For example, there are applications in which a specific non-zero temperature coefficient is at the specified Reference voltage is necessary, for example for the purpose to match the characteristics of different circles. Furthermore, the control function described above can be used in applications where different output voltages for individual units of a Qruppe are necessary, each of these output voltages being a

different temperature compensation is required. The specific The manner in which the invention is used therefore depends on the problem to be solved in the particular application away.

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In the case of Figure 1, a circuit used to provide zero temperature compensation, the numerical values for and Q can be obtained by entering experimentally determined values for Eq. (7A) and (8A) V _K and T _K begins, along with the known value of V _Q0 , a calculated value for £ (using the definition in equation (IA) with a known value of V.), and the desired value of V, the values for V " _K and T" were determined experimentally on the basis of voltage temperature measurements on a large number of Zener diodes, with typical extra-polar values being: V _K = U, Tk and Tj, = -383 ⁰ K. The value of V _beQ is 0.655 and the value for T _Q = 300 K. Using a specific value V s ίο the proportionality factors;

C = 0.1960
° = 0.7220.

By now choosing the resistors 26, 28 and 30 accordingly so that one contains Bas is voltages V. ^ and V. ₂ of 1.960 and 7.220 volts, the circuit arrangement according to Fig.l gives an optimal temperature compensation if one or the other emitter resistor R ^ or R ₂ is set so that the specific output voltage of 10 volts results. Which of the resistors R ₂ or R _{1 is} trimmed depends on whether the initial measurement of the output voltage gives a value that is below or above 10 volts.

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For an experimentally measured range of ° ^ with a large number of units of the class of Zener diodes produced by an IC process, as described in this application, the corresponding values of R ₂ ZR _{1 are} of practical interest In equation (2A) replacing the measured range of values for (J * corresponding to the measured Zener voltages of V (at 300 ⁰ K) from 6.0 to 6.6, it was found that:

The minimum of R ₃ ZR ₁ «1.966 (for V _g = 6.0)

and

the maximum of R ₃ ZR ₁ ■ 2.426 (for V _z = 6.6) is.

FIG. 2 shows details of a preferred embodiment of the circuit for the reference voltage which includes the arrangement of FIG. 1 and which operates in accordance with that described above. In FIG. 2, the elements Q ₁₁₂ ^and Q113 form ^the basic elements of the operational amplifier 14. The Zener diode Dp has Kelvin connections, the force and sense electrodes being essentially at the same potential. One of the electrodes is connected to the inverting input terminal 16 and the other of the electrodes via a resistor R ₁ I ₄₅ (reference number 18 in FIG. 1) to the common line 20 * The transistors Q ₁₁ C and Q ₁₁ correspond to the Transistors Q ₂ and Q ₁ of Flg. 1, resistors R ₁₅ Q and resistors R ₂ , R ₁ , resistors to resistors 26, 28 and 30.

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The amplifier circuit of Fig. 2 is substantially balanced symmetrically. Transistor Q _lo7 outputs a collector current to transistors Q ₁₁₂ and Q ₁₁₃ . The collector of Q ₁₁₁ . receives the emitter currents from Q ₁₁₂ ^{un (i} ^ i 13 ^and ß ^ ^b ^ ^e * ^ne adjustment in order to set the total current correctly. The base Q _111. is controlled by the current of the left-hand collector of Q ₁₀₇ above the voltage _-translator Q 1o q and the Plnch resistor R ₁₁ J ₀ controlled.

^ Io9 ^and ^ Ho ^{öin (} * buffer transistors. The current in Q _lo q is controlled by Q _{1 K} , which is balanced with Q. 1.

^xo ? ^1OH through

before giving currents. The Q ₁ .. current goes _{through / Q 1} g balanced with Q _lo7 so that the current through Q ₁₀₇ and the current through Q _{1 Q are} equal and also equal to the current of Q ₁₁₁ . As a result, even if the base currents of Q ₁ Q and Q ₁₁ ^ may contain errors, these errors can be compensated for with respect to Q ₁₁₂ and Q ₁₁ T * so that they tend to differ because of circuit symmetry wipe out.

Q ₁ , carries some additional current _{needed by Q 11} C and Q ₁₁ ^. Q ₁₁₁ provides protection for the output buffer Q ₁₁₀ . The left-hand emitter of Q ₃ - serves to jump-start the circuit.

FIG. 3 graphically shows the relationships between voltage and temperature discussed above in relation to FIG and which serve to achieve an optimum of temperature compensation when setting the reference output voltage to their specific Guarantee value.

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2 9 3 8 8 Λ 9

The illustration shows two straight lines Z. and Z ₂ , which represent the boundary lines of the region of the voltage-temperature characteristic curves of a large number of "buried" Zener diodes. The slope of these lines (p (, ^ and ch ₂ ) represent the derivative of the voltage-temperature relationship discussed above. An extra polarization of these lines (and lines not shown for intervening data) to the left results in a cut in a common area; centered around a specific voltage V _K and a corresponding temperature T _R. (It should be noted that for the measured data presented here, the intersection is at a temperature which is below absolute zero, making it none has physical meaning, but has a significant influence on the concept.) With a common point of intersection and the equation of the straight lines, the voltage-temperature equation of this Zener diode class used as a voltage source, as already stated above, can be represented as follows :

^V dev ^{s V} K ⁺ ώ CT - T _K ) where oO represents the slope of each curve.

Fig. 3 shows two additional straight lines J. and J ₂ , which indicate the range of the voltage-temperature characteristic curves for the voltage which is combined with the Zener voltage and which is derived from the compensation voltage source arrangement 2k , the one contains pn junction with a "band gap". These lines also intersect in a common area and the control circuit of the compensating voltage source arrangement is constructed in such a way that this common area in a

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Temperature of T _K lies, that is, on the same vertical line on which the common area of the intersection of the Zener characteristic curves Z ₁ and Zp lies. The control circuit is further arranged to place the common intersection on the compensation _{voltage Vj which is of such magnitude that when V i is combined with V R} the composite voltage is equal to the specified reference output voltage, in this case 10 volts .

In the present arrangement, therefore, setting the diffraction voltage in order to obtain a specified output value of 10 volts by changing the slope of the compensation voltage source lines within the range between J ₁ and J automatically results in a finally set slope of the curve J _n , which is an inversely matched, ie, a complementary relationship to the slope of the line Z "of the characteristic curve of the particular Zener diode which forms the base source for the reference voltage. In this way, the temperature coefficient of the diffraction voltage is optimized to or very close to zero by trimming the output voltage to the specified value of 10 volts.

While a specific preferred embodiment of the invention has been described in detail herein, it is it is understood that the invention is not limited thereto, but that other embodiments are within the scope of the invention are possible. It will thus be understood that the invention can be used in a wide variety of types to compensate for ground voltage sources, and that the compensation

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sationsordnung the most varied types of compensation voltage source arrangements that are connected to the basic voltage source work, can use * A wide variety of control circuits can still be provided to support the basic concept of the To Carry Out Invention «The invention disclosed herein can stimulate the skilled person to a wide variety of applications.

A temperature compensated IC reference voltage has been described herein which has a zener diode which is used as a basic voltage source is used in connection with a compensation voltage source, with a transistor, which has a forward biased pn-junction and in connection with a control circuit · The compensation voltage is with the Zener voltage is added up in order to specify a reference voltage. «The compensation voltage source has an adjustment element to set the reference output voltage to a specified value to trim, and the control circuit works with the adjustment element in such a way that it automatically generates an optimal temperature compensation when the reference output voltage to the specified value is set.

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attachment

Since the input terminals of the amplifier 14 are at the same potential the following equations can be written as follows:

-vs £ v -v - R (r V ^v z O ^v _o ^v be "l M ^v o

? 2

V -XV + A * Tf * V s V - V + -, V

^v o $ ^v o * "l ^v o ^v z ^v be R,» ^v be

Rp ο

v _o (ι - 4 ♦ * ις) «v _z ♦ ας -ο v _be

R ₂
^V z ⁺ (^ - ¹ ^ ^V be

1 - <6 + f ^R 2

(IA)

, - dV ^ R ₀ dV.

/ ζ / 2 ^ x be -τ

3τ ~ ^ rT "^; ^ ^-

^R l

dV / dT dV

- = -, where —2 = ο

dV _be / dT dT

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R _{2 1} ^d V ^{/ dT}

^{let V} z " ^V

dT

let V _be = V ₀₀ -

v _b . ■ -r

dT

^dV be

Ro o6 (2A)

By inserting these values for V _g and R ₂ ZR ₁ into equation (IA), the result is

_v . v *** ^CT - ■ ν * p

° "ι - S + ε ei ♦ Ot ₁

resolving the counter results in:

v _K -ob t _k ♦ - v _go

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so that the stress is a function of ei according to the relation:

V ₁ , + οΛ (- ^ - T ")

^ν ο ⁼ ■ ■ · ■ ^ . . V _K , Τ _κ , ^, f »A *" ^{5 K} ° nstants

By taking the derivatives according to ^, we get:

- ^t k) - Γν _κ ^ (^ - ^t k) _7 | -

Γ ι -Λ + £ (ι ♦

By setting the derivatives equal to zero and the equation dissolves, results in:

^ ² - f ' - ^s ^ (5A)

^v k ^v k 1

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Claims (5)

PATENT ^{Attorney DiPUNG} HELMUT GÖRTZ 2938849 6 Fron'klurl am Main 70 Schn «ckenho (slr. 77 - valley. 617079 ANALOG DEVICES, INCORPORATED 2k . September 1979 GzW / goe Temperature compensated IC reference voltage Claims ( l, j arrangement for generating a temperature-compensated supply reference signal for a solid, characterized by a first supply signal source arrangement which produces a first signal which follows a signal temperature characteristic curve with a first slope; by a second supply signal source arrangement which has a generates a second signal which is combined with the first signal so as to generate a composite reference output signal which is dependent on the first and second signals, the second signal following a signal-temperature characteristic curve with a second slope; which cooperate with the second supply signal source arrangement and comprise an adjustment arrangement for the purpose of varying this second signal so as to bring the composite reference output signal accordingly to a specified value; this control circuit arrangement of the 030016/0707 Adjusting arrangement has controlled arrangements, for the purpose Varying the second slope when the second signal is changed by a predetermined temperature coefficient for the composite signal when it is set to the specified value. 2. Arrangement according to claim 1, characterized in that that the control arrangement is so constructed that it has the temperature coefficient zero for the composite Signal when it reaches the specified value. 3. Arrangement according to claim 2, characterized in that that the control circuit arrangement is so constructed that there is an inverse vote between the two Slopes generated when the composite signal denotes the specified value is reached so as to achieve a temperature coefficient of zero at that level. 1. Arrangement according to claim 1 or one of the following, characterized in that the first Voltage source arrangement comprises a Zener diode, and that the second voltage source arrangement has an arrangement for generating a compensation signal which is a function of the base-emitter voltage of a semiconductor junction. 5. Arrangement according to claim 4, characterized in that that the adjustment means have a variable resistance in series with this transition. 030016/0707 Method for temperature compensation of the signal of a solid state supply signal source, by connecting a second signal source arrangement to this, which generates a second signal generated in such a way that a reference signal is generated which is based on the first and second signals are responsive, and wherein the signal-temperature characteristic curves of the two signals are opposite Have signs so that the temperature effects tend to be reflected in the reference signal extinguish, characterized in that to achieve temperature compensation for a reference signal at a specified value, the circuit elements coupled to the second signal source arrangement can be set to change the second signal while keeping the reference signal at the specified value set and characterized by controlling the slope of the characteristic signal temperature curve of the second signal by the setting of the circuit element so as to have a predetermined relationship between the effects on the reference signal to establish the temperature characteristics of the first and second signals, so as to specify a predetermined temperature coefficient for the reference signal when this is on the specified Value is set. 030016/0707