SENSOR CIRCUIT HAVING A COMPENSATING RESISTOR FOR COMPENSATING A TEMPERATURE COEFFICIENT OF A BRIDGE CIRCUIT

Abstract

The present disclosure relates to a sensor circuit, including a first connection, a second connection and a bridge circuit, which is connected between the first connection and the second connection, having a plurality of bridge resistors with a respective temperature coefficient. The bridge circuit has a measurement sensitivity and a temperature coefficient of measurement sensitivity and a bridge offset with a temperature coefficient of the bridge offset. The sensor circuit further includes at least one compensating resistor, which is connected between the first connection and the second connection, with a temperature coefficient that differs from the temperature coefficient of the bridge resistors.

Claims

1. A sensor circuit, comprising a first connection; a second connection; a bridge circuit, which is connected between the first connection and the second connection, having a plurality of bridge resistors with respective temperature coefficients, wherein the bridge circuit has a measurement sensitivity with a temperature coefficient of measurement sensitivity and a bridge offset with a temperature coefficient of the bridge offset; and at least one compensating resistor, which is connected between the first connection and the second connection, with a temperature coefficient that differs from the respective temperature coefficients of the plurality of bridge resistors.

2. The sensor circuit as claimed in claim 1, wherein the at least one compensating resistor is measurement-variable-independent.

3. The sensor circuit as claimed in claim 1, wherein the at least one compensating resistor is connected between the first connection and the second connection and parallel to the bridge circuit.

4. The sensor circuit as claimed in claim 3, wherein a further compensating resistor is connected in the bridge circuit in series to a bridge resistor, of the plurality of bridge resistors.

5. The sensor circuit as claimed in claim 1, wherein the temperature coefficient of measurement sensitivity of the bridge circuit is negative, the respective temperature coefficients of the plurality of bridge resistors are negative and the temperature coefficient of the at least one compensating resistor is positive.

6. The sensor circuit as claimed in claim 1, wherein the temperature coefficient of measurement sensitivity of the bridge circuit is positive, the respective temperature coefficients of the plurality of bridge resistors are negative and the temperature coefficient of the at least one compensating resistor is less than the respective temperature coefficients of the plurality of bridge resistors.

7. The sensor circuit as claimed in claim 1, wherein the temperature coefficient of measurement sensitivity of the bridge circuit is negative, the respective temperature coefficients of the plurality of bridge resistors are positive and the temperature coefficient of the at least one compensating resistor is greater than the respective temperature coefficients of the plurality of bridge resistors.

8. The sensor circuit as claimed in claim 1, wherein the temperature coefficient of measurement sensitivity of the bridge circuit is positive, the respective temperature coefficients of the plurality of bridge resistors are positive and the temperature coefficient of the at least one compensating resistor is negative.

9. The sensor circuit as claimed in claim 1, wherein the at least one compensating resistor is connected in the bridge circuit in series to a bridge resistor of the plurality of bridge resistors.

10. The sensor circuit as claimed in claim 1, wherein the at least one compensating resistor is connected in series to the bridge circuit.

11. The sensor circuit as claimed in claim 10, wherein a further compensating resistor is connected in the bridge circuit in series to a bridge resistor of the plurality of bridge resistors.

12. The sensor circuit as claimed in claim 11, wherein the further compensating resistor is connected between an output signal connection of the bridge circuit and one of the first connection or the second connection.

13. The sensor circuit as claimed in claim 10, wherein the temperature coefficient of measurement sensitivity of the bridge circuit is negative and the at least one compensating resistor has a smaller temperature coefficient than the respective temperature coefficients of the plurality of bridge resistors.

14. The sensor circuit as claimed in claim 10, wherein the temperature coefficient of measurement sensitivity of the bridge circuit is positive and the at least one compensating resistor has a greater temperature coefficient than the respective temperature coefficients of the plurality of bridge resistors.

15. The sensor circuit as claimed in claim 1, wherein the bridge circuit has a first half bridge and a parallel second half bridge.

16. The sensor circuit as claimed in claim 1, wherein the plurality of bridge resistors of the bridge circuit are designed as xMR resistors.

17. The sensor circuit as claimed in claim 16, wherein the plurality of bridge resistors are designed as TMR resistors.

18. A sensor circuit, comprising: a constant-current source; a ground connection; a bridge circuit, that is connected between the constant-current source and the ground connection, comprising at least one half bridge having a first xMR resistor and a second xMR resistor, which have a negative temperature coefficient in each case; and at least one compensating resistor with positive temperature coefficient, which is connected between the constant-current source and the ground connection and parallel to the bridge circuit.

19. The sensor circuit as claimed in claim 18, wherein a further compensating resistor is connected in the half bridge in series to the first xMR resistor and the second xMR resistor, wherein the further compensating resistor has a temperature coefficient which differs from the negative temperature coefficient of the first xMR resistor and the second xMR resistor.

20. (canceled)

21. A sensor circuit, comprising: a constant-voltage source; a ground connection; a bridge circuit comprising at least one half bridge having a first xMR resistor and a second xMR resistor which in each case have a negative temperature coefficient; and at least one compensating resistor with a negative temperature coefficient, wherein the negative temperature coefficient of the at least one compensating resistor is smaller than the negative temperature coefficient of the first xMR resistor or the second xMR resistor, wherein the at least one compensating resistor is connected between the constant-voltage source and the bridge circuit and the bridge circuit is connected between the at least one compensating resistor and the ground connection, or wherein the at least one compensating resistor is connected between the bridge circuit and the ground connection and the bridge circuit is connected between the constant-voltage source and the at least one compensating resistor.

22. (canceled)

23. (canceled)

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Some examples of devices and/or methods are explained in more detail below merely by way of example with reference to the accompanying figures. In the figures:

[0040] FIG. 1 shows a conventional sensor bridge circuit;

[0041] FIG. 2 shows a relationship between measurement sensitivity temperature coefficient and offset drift;

[0042] FIG. 3 shows a sensor circuit having a compensating resistor according to a first example implementation;

[0043] FIG. 4 shows a relationship V.sub.Br(T)/V.sub.Br(T=0) and a relationship S.sub.B0(T)/S.sub.B0(T=0) for various temperature differences T with respect to a reference temperature and for different compensating resistors;

[0044] FIG. 5 shows a relationship V.sub.Br(T)/V.sub.Br(T=0) and a relationship S.sub.B0(T)/S.sub.B0(T=0) for various temperature differences T with respect to a reference temperature and for different compensating resistors;

[0045] FIG. 6 shows a sensor circuit having a compensating diode according to a further example implementation;

[0046] FIG. 7 shows relationships of temperature coefficient of Zener voltage for various temperature differences (%/ C.) and (mV/ C.);

[0047] FIG. 8 shows a sensor circuit having a compensating resistor according to a further example implementation;

[0048] FIG. 9 shows a relationship V.sub.Br(T)/V.sub.Br(T=0) and a relationship S.sub.B0(T)/S.sub.B0(T=0) for various temperature differences T with respect to a reference temperature and for different compensating resistors;

[0049] FIG. 10 shows a sensor circuit having a compensating diode according to a further example implementation;

[0050] FIG. 11 shows a sensor circuit having a compensating resistor according to a further example implementation;

[0051] FIG. 12 shows effects of the compensating resistor according to FIG. 11 on an output voltage offset;

[0052] FIG. 13 shows a sensor circuit according to a further example implementation; and

[0053] FIG. 14 shows further sensor circuits according to example implementations.

DETAILED DESCRIPTION

[0054] Some examples are now described in more detail with reference to the accompanying figures. Further possible examples are however not restricted to the features of these implementations that are described in detail. These may contain modifications of the features and equivalents and alternatives to the features. The terminology used herein to describe particular examples is also not intended to be restrictive for further possible examples.

[0055] The same or similar reference signs relate, throughout the description of the figures, to the same or similar elements or features, which may each be implemented identically or else in a modified form, while providing the same or a similar function. In the figures, the thicknesses of lines, layers and/or regions may also be exaggerated for clarification.

[0056] When two elements A and B are combined using an or, this is to be understood as meaning that all possible combinations are disclosed, e.g., only A, only B, and also A and B, unless expressly defined otherwise in the individual case. At least one of A and B or A and/or B may be used as alternative wording for the same combinations. This applies equivalently to combinations of more than two elements.

[0057] If a singular form, e.g., a, an and the, is used, and the use of only a single element is neither explicitly nor implicitly defined as mandatory, other examples may also use multiple elements to implement the same function. When a function is described in the following as being implemented using multiple elements, further examples may implement the same function using a single element or a single processing entity. Furthermore, it is understood that the terms comprises, comprising, has and/or having when used describe the presence of the indicated features, whole numbers, steps, operations, processes, elements, components and/or a group thereof, but do not thereby exclude the presence or the addition of one or more further features, whole numbers, steps, operations, processes, elements, components and/or a group thereof.

[0058] FIG. 1 shows an example of a sensor circuit 100. A physical variable can be measured using the sensor circuit 100. For example, the sensor circuit 100 may be a magnetic field sensor circuit for measuring an external magnetic field.

[0059] The sensor circuit 100 comprises a supply connection 110, a ground connection 120 and a measuring bridge circuit 130 that is connected between the supply connection 110 and the ground connection 120. The measuring bridge circuit 130 comprises a first half bridge that is connected between the supply connection 110 and the ground connection 120, having a series circuit made up of measurement-variable-dependent resistors R.sub.1 and R.sub.2 and, parallel thereto, a second half bridge that is connected between the supply connection 110 and the ground connection 120, having a series circuit made up of measurement-variable-dependent resistors R.sub.3 and R.sub.4. In the example implementation shown, the resistors R.sub.1 to R.sub.4 are magnetoresistive resistors, particularly TMR resistors with the different reference magnetizations of the two half bridges illustrated in FIG. 1.

[0060] A first output signal connection V.sub.out1 is located between the resistors R.sub.1 and R.sub.2 of the first half bridge. A second output signal connection V.sub.out2 is located between the resistors R.sub.3 and R.sub.4 of the second half bridge. A differential voltage between the two output signal connections V.sub.out1 and V.sub.out2 represents a measurement-variable-dependent (e.g., magnetic-field-dependent) bridge output voltage V.sub.out of the sensor circuit 100.

[0061] A measurement sensitivity S.sub.B_Br of the measuring bridge circuit 130 can be defined as a change V.sub.out of the bridge output voltage V.sub.out in the case of a change B of an applied external magnetic field (measurement variable):

[00005]$S_{\mathrm{B\_Br}}:=\left(V_{\mathrm{out}}\right)/B$

[0062] The bridge output voltage V.sub.out is dependent on a voltage V.sub.Br between supply connection 110 and ground connection 120 across the entire (measuring) bridge circuit 130. The measurement sensitivity S.sub.B_Br of the bridge circuit 130 is therefore proportional to V.sub.Br:

[00006]$S_{\mathrm{B\_Br}}{V}_{Br}.$

[0063] In the case of a supply with constant supply current I.sub.DD, the voltage is

[00007]$V_{Br}=I_{DD}.Math.R_{Br},$

[0064] where R.sub.Br means the total resistance of the bridge circuit 130, where

[00008]$R_{Br}=\frac{\left(R1+R2\right).Math.\left(R3+R4\right)}{\left(R1+R2\right)+\left(R3+R4\right)}.$

[0065] If the bridge circuit 130 is supplied with a constant current I.sub.DD as supply signal, as may be required in certain applications, the temperature coefficient TC.sub.R_Br of the total resistance R.sub.Br influences the bridge voltage V.sub.Br. The temperature coefficient TC.sub.R_Br of the total resistance is in turn dependent on the temperature coefficient TC.sub.R of the individual measurement-variable-dependent bridge resistors R.sub.1 to R.sub.4.

[0066] In the case of a negative temperature coefficient (TC.sub.SB_TMR<0) of measurement sensitivity of the bridge resistors R.sub.1 to R.sub.4, a temperature coefficient TC.sub.SB_Br of measurement sensitivity of the bridge circuit 130 also has a negative sign. In the case of a negative temperature coefficient (TC.sub.R<0) of the individual bridge resistors R.sub.1 to R.sub.4, the total resistance R.sub.Br of the bridge circuit 130 between the supply connections 110, 120 likewise has a negative temperature coefficient TC.sub.R_Br<0.

[0067] The temperature coefficient TC.sub.SB_Br of measurement sensitivity of a sensor bridge that is supplied with constant current is therefore:

[00009]${\mathrm{TC}}_{\mathrm{SB\_Br}}={\mathrm{TC}}_{\mathrm{SB\_TMR}}+{\mathrm{TC}}_{\mathrm{R\_Br}}$

[0068] As these two temperature coefficients TC.sub.SB_TMR and TC.sub.R_Br for TMR bridge resistors are generally negative, their effects add up and the temperature characteristics of a current-fed sensor becomes poorer overall than that of a voltage-fed sensor bridge.

[0069] Furthermore, due to TC.sub.SB_TMR, a magnetic field B.sub.OP, in which the output voltages V.sub.out1, V.sub.out2 of the two half bridges (with different reference magnetizations) are identical, V.sub.out1=V.sub.out2, also shifts, and therefore the differential bridge output voltage V.sub.out=0. In the case of a change of the intrinsic measurement sensitivity (SB.sub.TMR) of the bridge circuit, V.sub.out1=V.sub.out2 shifts to BB.sub.OP. At B.sub.OP, a non-vanishing bridge output voltage V.sub.out0, that is to say an offset drift, then occurs. Consequently, the temperature coefficient of measurement sensitivity TC.sub.SB_TMR of the bridge circuit 130 also leads directly to a temperature coefficient of the offset TC.sub.Off of the bridge circuit 130. This relationship is shown in FIG. 2.

[0070] Example implementations of the present disclosure aim to compensate the temperature coefficient of measurement sensitivity TC.sub.SB_TMR of the sensor bridge circuit 130 at least to some extent and therefore to obtain a sensor circuit ideally with a vanishing temperature coefficient of measurement sensitivity (at least reduced in terms of absolute value). Various example implementations are described in the following.

[0071] The sensor circuit 300 shown in FIG. 3 is fed using the supply connection 110 by a constant current I.sub.DD (constant-current source) and further comprises a compensating resistor 140 (R.sub.comp) that is connected between the supply connection 110 and the ground connection 120. The compensating resistor R.sub.comp is configured to compensate the temperature coefficient of measurement sensitivity (measurement sensitivity temperature coefficient) TC.sub.SB_Br of the bridge circuit 130 at least to some extent. To this end, the compensating resistor R.sub.comp is ideally measurement-variable-independent (e.g., magnetic-field-independent), that is to say in the case of magnetoresistive bridge resistors R.sub.1 to R.sub.4 is not magnetoresistive for example. Furthermore, the compensating resistor R.sub.comp has a different temperature coefficient of the compensating resistor TC.sub.Rcomp than the temperature coefficient TC.sub.R of the bridge resistors R.sub.1 to R.sub.4, e.g., TC.sub.RcompTC.sub.R. Depending on the application or requirement, TC.sub.Rcomp can be greater or less than TC.sub.R.

[0072] In the example shown, the resistance temperature coefficient TC.sub.R of the bridge resistors R.sub.1 to R.sub.4 is negative (here: 800 ppm/K). A negative resistance temperature coefficient TC.sub.R_Br of the total resistance R.sub.Br of the bridge circuit 130 also results from this. Furthermore, in the example shown, the measurement sensitivity temperature coefficient TC.sub.SB_Br of the bridge circuit 130 is negative (TC.sub.SB_Br<0).

[0073] In the sensor circuit 300 of FIG. 3, the compensating resistor R.sub.comp is connected between the supply signal connection 110 and the ground connection 120 and parallel to the bridge circuit 130. At a constant supply current I.sub.DD, the voltage drop V.sub.Br over the bridge circuit 130 decreases with increasing temperature. If the compensating resistor R.sub.comp with positive resistance temperature coefficient TC.sub.Rcomp (TC.sub.Rcomp>0) is chosen, the negative TC.sub.R_Br of the bridge circuit 130 can be compensated at least to some extent or entirely by the parallel connection of the compensating resistor R.sub.comp. Therefore, in a bridge circuit 130 with negative TC.sub.R Br, the compensating resistor R.sub.comp can be configured as a resistor with positive temperature coefficient (PTC thermistor). Therefore, the bridge voltage V.sub.Br and the output voltage V.sub.out can be stabilized over the temperature. A stabilized output voltage V.sub.out then in turn leads to a stabilized measurement sensitivity S.sub.B_Br of the bridge circuit 130 over the temperature in accordance with TC.sub.SB_Br=TC.sub.SB_TMR+TC.sub.R_Overall,

where TC.sub.R_Overall means the resistance temperature coefficient of the parallel circuit made up of bridge circuit 130 and compensating resistor R.sub.comp.

[0074] The compensating resistance R.sub.comp can according to some example implementations be chosen in an order of magnitude of the bridge resistances R.sub.1 to R.sub.4. If the bridge resistances R.sub.1 to R.sub.4 are for example 4 k in each case, then the compensating resistance R.sub.comp can for example be chosen in a range of 1 k<R.sub.comp<10 k. Possible materials for the compensating resistor R.sub.comp are metals, PTC thermistors (PTC resistors), NTC thermistors (NTC resistors), polymer PTC thermistors, or (highly doped) polysilicon.

[0075] FIG. 4 (top) shows the resulting relationship V.sub.Br(T)/V.sub.Br(T=0) for various temperature differences T with respect to a reference temperature. FIG. 4 (bottom) shows the resulting relationship S.sub.B0(T)/S.sub.B0(T=0) for various temperature differences T. In this case, by way of example R.sub.1=R.sub.2=R.sub.3=R.sub.4=4 k was assumed. In the example shown, the best stabilization of the bridge voltage V.sub.Br and the measurement sensitivity of the sensor bridge was achieved for R.sub.comp=2 k and TC.sub.Rcomp=+800 ppm/K. Even for TC.sub.Rcomp=0, better stabilizations were achieved for R.sub.comp=2 k and R.sub.comp=4 k than without a compensating resistor R.sub.comp. Example implementations are therefore also conceivable, in which TC.sub.Rcomp<0, but TC.sub.Rcomp>TC.sub.R, for which the resistance temperature coefficient TC.sub.R of the bridge resistors R.sub.1 to R.sub.4 is therefore negative (TC.sub.R<0), the measurement sensitivity temperature coefficient of the bridge circuit 130 is negative (TC.sub.SB_Br<0) and the resistance temperature coefficient of the compensating resistor is negative (TC.sub.Rcomp<0), but greater than TC.sub.R (TC.sub.Rcomp>TC.sub.R).

[0076] FIG. 5 shows similar curves to FIG. 4 for R.sub.comp=2 k or 4 k and TC.sub.Rcomp=0 ppm/K or TC.sub.Rcomp=+3000 ppm/K.

[0077] In the case of measurement-variable-dependent bridge resistors R.sub.1 to R.sub.4 with in each case a positive resistance temperature coefficient TC.sub.R, example implementations of the sensor circuit 300 are also conceivable, in which the resistance temperature coefficient TC.sub.R of the bridge resistors R.sub.1 to R.sub.4 is positive (TC.sub.R>0), the measurement sensitivity temperature coefficient of the bridge circuit 130 is positive (TC.sub.SB_Br>0) and the resistance temperature coefficient of the compensating resistor is negative (TC.sub.Rcomp<0). Furthermore, example implementations are conceivable, in which the resistance temperature coefficient TC.sub.R of the bridge resistors R.sub.1 to R.sub.4 is positive (TC.sub.R>0), the measurement sensitivity temperature coefficient of the bridge circuit 130 is positive (TC.sub.SB_Br>0) and the resistance temperature coefficient of the compensating resistor is positive (TC.sub.Rcomp>0), but less than TC.sub.R (TC.sub.Rcomp<TC.sub.R 0).

[0078] Furthermore, example implementations of the sensor circuit 300 are also conceivable, in which the measurement sensitivity temperature coefficient of the bridge circuit 130 is positive (TC.sub.SB_Br>0), the resistance temperature coefficient TC.sub.R of the bridge resistors R.sub.1 to R.sub.4 is negative (TC.sub.R<0) and the resistance temperature coefficient of the compensating resistor is less than the resistance temperature coefficient of the bridge resistors (TC.sub.Rcomp<TC.sub.R). Furthermore, example implementations are conceivable, in which the measurement sensitivity temperature coefficient of the bridge circuit is negative (TC.sub.SB_Br<0), the resistance temperature coefficient of the bridge resistors is positive (TC.sub.R>0) and the resistance temperature coefficient of the compensating resistor is greater than the resistance temperature coefficient of the bridge resistors (TC.sub.Rcomp>TC.sub.R).

[0079] In a sensor bridge circuit 130 that is fed by a constant current I.sub.DD, an additional resistor R.sub.comp can therefore be connected parallel to the sensor bridge circuit 130. The constant supply current I.sub.DD is divided between the additional compensating resistor R.sub.comp and the sensor bridge circuit 130. If the temperature coefficient TC.sub.Rcomp of the compensating resistor is greater than the temperature coefficient TC.sub.R_Br of the total bridge resistance, the temperature coefficient of the complete circuit 300 is greater than without compensating resistor R.sub.comp, which leads to a more stable bridge voltage V.sub.out over the temperature. Using a large positive TC.sub.Rcomp of the compensating resistor R.sub.comp, a positive temperature coefficient can also be achieved for the total system resistance, which leads to an increasing bridge voltage over the temperature. This can be used to compensate the negative temperature coefficient of measurement sensitivity that is to be observed in the case of constant bridge voltage.

[0080] In some implementations, the compensating resistor R.sub.comp may comprise a component (or a group of components) that provide a change of resistance in a manner similar to that described above with respect to FIGS. 1-5. In some implementations, the compensating resistor R.sub.comp may comprise a non-ohmic component.

[0081] The sensor circuit 600 shown in FIG. 6 is fed using the supply connection 110 by a constant current I.sub.DD (constant-current source) and further comprises a compensating diode 605 (D.sub.comp) that is connected between the supply connection 110 and the ground connection 120. The compensating diode D.sub.comp is configured to compensate the temperature coefficient of measurement sensitivity (measurement sensitivity temperature coefficient) TC.sub.SB_Br of the bridge circuit 130 at least to some extent. To this end, the compensating diode D.sub.comp is ideally measurement-variable-independent (e.g., magnetic-field-independent), that is to say in the case of magnetoresistive bridge resistors R.sub.1 to R.sub.4 is not magnetoresistive for example. Furthermore, the compensating diode D.sub.comp has a different temperature coefficient of the compensating diode TC.sub.Dcomp than the temperature coefficient TC.sub.R of the bridge resistors R.sub.1 to R.sub.4, e.g., TC.sub.DcompTC.sub.R. Depending on the application or requirement, TC.sub.Dcomp can be greater or less than TC.sub.R.

[0082] FIG. 7 (left) shows the resulting relationships of temperature coefficient of Zener voltages Y.sub.z for various temperature differences (%/ C.). FIG. 7 (right) shows the resulting relationships of temperature coefficient of Zener voltages Y.sub.z for various temperature differences (mV/ C.).

[0083] The sensor circuit 800 shown in FIG. 8 is fed by a constant supply voltage V.sub.DD (constant-voltage source) and comprises a compensating resistor 140 (R.sub.comp) that is connected between the supply connection 110 and the bridge circuit 130. The compensating resistor R.sub.comp is therefore also connected between supply connection 110 and ground connection 120 herebut as a series resistor instead of as a parallel resistor. The compensating resistor R.sub.comp is also configured here to compensate the temperature coefficient of measurement sensitivity (measurement sensitivity temperature coefficient) TC.sub.SB_Br of the bridge circuit 130 at least to some extent. To this end, the compensating resistor R.sub.comp is ideally measurement-variable-independent (e.g., magnetic-field-independent), that is to say for example not magnetoresistive. Furthermore, compensating resistor R.sub.comp has a different temperature coefficient of the compensating resistor TC.sub.Rcomp than the temperature coefficient TC.sub.R of the bridge resistors R.sub.1 to R.sub.4, e.g., TC.sub.RcompTC.sub.R.

[0084] In the example shown in FIG. 8, the resistance temperature coefficient TC.sub.R of the bridge resistors R.sub.1 to R.sub.4 is negative (here: 800 ppm/K). A negative resistance temperature coefficient TC.sub.R_Br of the total resistance R.sub.Br of the bridge circuit 130 also results from this. Furthermore, in the example shown, the measurement sensitivity temperature coefficient TC.sub.SB_Br of the bridge circuit 130 is likewise negative (TC.sub.SB_Br<0).

[0085] In the sensor circuit 800 of FIG. 8, the measurement-variable-independent compensating resistor R.sub.comp is connected between the supply signal connection 110 and the bridge circuit 130 and has a resistance temperature coefficient TC.sub.Rcomp which is smaller (more negative) than the resistance temperature coefficient TC.sub.R of the bridge resistors R.sub.1 to R.sub.4 (TC.sub.Rcomp<TC.sub.R). According to FIG. 8, the measurement sensitivity temperature coefficient TC.sub.SB_Br of the bridge circuit 130 is therefore negative, the compensating resistor is essentially measurement-variable-independent and has a smaller resistance temperature coefficient TC.sub.Rcomp than the resistance temperature coefficient TC.sub.R of the bridge resistors. As a result, at a constant supply voltage V.sub.DD, the voltage drop because of the compensating resistor R.sub.comp is stronger than the voltage drop because of the bridge circuit 130. At a constant supply voltage V.sub.DD, the voltage drop V.sub.Br because of the bridge circuit 130 therefore increases with increasing temperature. This is shown in FIG. 9 (top), which shows the resulting relationship V.sub.Br(T)/V.sub.Br(T=0) for various temperature differences T. FIG. 9 (bottom) shows the resulting measurement sensitivity relationship S.sub.B0(T)/S.sub.B0(T=0) for various temperature differences T. The different curves of FIG. 7 relate to different R.sub.comp of 0 k to 8 k and TC.sub.Rcomp=0 ppm/K or TC.sub.Rcomp=1600 ppm/K.

[0086] If the compensating resistor R.sub.comp with resistance temperature coefficient TC.sub.Rcomp<TC.sub.R is chosen, the negative TC.sub.R_Br of the bridge circuit 130 can be compensated at least to some extent or entirely. Due to the bridge voltage V.sub.Br increasing with T>0, the output voltage V.sub.out can be stabilized over the temperature in spite of falling bridge resistances R.sub.1 to R.sub.4. A stabilized output voltage V.sub.out then in turn leads to a stabilized measurement sensitivity S.sub.B_Br of the bridge circuit 130 over the temperature (see FIG. 9 (bottom)).

[0087] In the case of measurement-variable-dependent bridge resistors R.sub.1-R.sub.4 in each case with a positive resistance temperature coefficient TC.sub.R, example implementations of the sensor circuit 800 are also conceivable, in which the measurement sensitivity temperature coefficient TC.sub.SB_Br of the bridge circuit 130 is positive (TC.sub.SB_Br>0), the compensating resistor R.sub.comp is measurement-variable-independent and has a greater resistance temperature coefficient TC.sub.Rcomp than the resistance temperature coefficient TC.sub.R of the bridge resistors (TC.sub.Rcomp>TC.sub.R).

[0088] If the bridge 130 is supplied with a constant supply voltage V.sub.DD, a series compensating resistor R.sub.comp with defined temperature coefficient TC.sub.Rcomp can be used to trim the bridge voltage V.sub.Br. With suitable values for resistance R.sub.comp and temperature coefficient TC.sub.Rcomp, this series resistor can compensate the temperature coefficient of sensitivity TC.sub.SB_TMR.

[0089] In the sensor circuit 1000 of FIG. 10, the measurement-variable-independent compensating diode D.sub.comp is connected between the supply signal connection 110 and the bridge circuit 130 and has a resistance temperature coefficient TC.sub.Dcomp which is smaller (more negative) than the resistance temperature coefficient TC.sub.R of the bridge resistors R.sub.1 to R.sub.4 (TC.sub.Dcomp<TC.sub.R). According to FIG. 10, the measurement sensitivity temperature coefficient TC.sub.SB_Br of the bridge circuit 130 is therefore negative, the compensating diode D.sub.comp is essentially measurement-variable-independent and has a smaller resistance temperature coefficient TC.sub.Dcomp than the resistance temperature coefficient TC.sub.R of the bridge resistors. As a result, at a constant supply voltage V.sub.DD, the voltage drop because of the compensating diode D.sub.comp is stronger than the voltage drop because of the bridge circuit 130. At a constant supply voltage V.sub.DD, the voltage drop V.sub.Br because of the bridge circuit 130 therefore increases with increasing temperature.

[0090] The sensor circuit 1100 shown in FIG. 11 is fed at the supply connection 110 by a constant supply current I.sub.DD and comprises a compensating resistor 140 (R.sub.2,series) that is connected in series in the first half bridge R.sub.1, R.sub.2. The compensating resistor R.sub.2,series is therefore connected in the bridge circuit 130 in series to the first resistor R.sub.1 and the second resistor R.sub.2. In the example shown, the compensating resistor R.sub.2,series is connected between the first output signal connection V.sub.out1 and the bridge resistor R.sub.2. Different arrangements of the compensating resistor inside the first half bridge are likewise conceivable. Likewise, the compensating resistor R.sub.2,series can be arranged in the second half bridge R.sub.3, R.sub.4.

[0091] The compensating resistor R.sub.2,series is therefore also connected here between supply connection 110 and ground connection 120. Furthermore, the compensating resistor R.sub.2,series is also configured here to compensate the measurement sensitivity temperature coefficient TC.sub.SB_Br of the bridge circuit 130 at least to some extent. To this end, the compensating resistor R.sub.2,series is ideally measurement-variable-independent (e.g., magnetic-field-independent), that is to say not magnetoresistive for example. Furthermore, the compensating resistor R.sub.2,series has a different temperature coefficient TC.sub.R2_series than the temperature coefficient TC.sub.R of the bridge resistors R.sub.1 to R.sub.4, e.g., TC.sub.R2_series #TC.sub.R.

[0092] In some implementations, the compensating resistor R.sub.2,series may comprise a component (or a group of components) that provide a change of resistance in a manner similar to that described above. In some implementations, the compensating resistor R.sub.2,series may comprise a non-ohmic component.

[0093] In FIG. 12, the output voltages V.sub.out1, V.sub.out2 of the half-bridge branches are illustrated depending on the B-field for the two cases with and without the additional compensating resistor R.sub.2,series. At room temperature (thin lines), V.sub.out1 and V.sub.out2 are identical at B=B.sub.OP, e.g., the bridge offset is equal to zero. For the case with the additional compensating resistor R.sub.2,series, the measurement-variable-dependent bridge resistor R.sub.2 must be adjusted in order to have offset=0 at B=B.sub.OP. The thick curves correspond to the output voltages V.sub.out1, V.sub.out2 at high temperature (HT). With a negative temperature coefficient of the bridge resistors, the total bridge resistance drops and the bridge voltage likewise drops at a constant supply current. Consequently, the output voltages V.sub.out1 and V.sub.out2 are reduced. A typically negative TC of sensitivity TC.sub.SB_TMR leads to a flatter V.sub.OUT vs. B-characteristics, which leads to a shift of the zero offset B-field to higher values. Consequently, the bridge offset at B.sub.OP is no longer zero, e.g., there is a TC.sub.Off originating from TC.sub.SB_TMR. The straight, bold lines designate the V.sub.OUT1/2 for the case without the additional compensating resistor R.sub.2,series.

[0094] If an additional compensating resistor R.sub.2,series with a positive resistance temperature coefficient TC.sub.R2,series is connected in series to the bridge resistor R.sub.2, the decrease of the total resistance of the bridge 130 and therefore also the decrease of V.sub.out1/2 lessens at higher temperatures, as can be seen in FIG. 11 (dashed bold lines). Furthermore, the resistance of the half bridge, in which the additional compensating resistor R.sub.2,series is located, has a smaller decrease of V.sub.OUT1 (line 1202) than the other half bridge V.sub.OUT2 (line 1204). The consequence of this is that the B-field in which V.sub.out1 and V.sub.out2 intersect is not so strongly shifted to higher values as without the additional compensating resistor R.sub.2,series (lines 1206, 1208). Consequently, the offset shift due to temperature and therefore also the TC.sub.Off is reduced. It can therefore be seen from FIG. 12 that the additional compensating resistor R.sub.2,series compensates the effect of the TC.sub.SB_TMR (to some extent). It is also possible to undertake overcompensation in order to achieve a change of sign of the TC.sub.Off, in that one correspondingly chooses the additional compensating resistor R.sub.2,series and its temperature coefficient.

[0095] The same effect could be achieved in that instead of the additional compensating resistor R.sub.2,series, an additional compensating resistor R.sub.1,series is connected in series to the bridge resistor R.sub.1, which then has a negative resistance temperature coefficient however. Alternatively, an additional compensating resistor R.sub.3,series with a positive resistance temperature coefficient could also be connected in series to R.sub.3. Then, the drop of V.sub.OUT2 would be increased at higher temperatures, which leads to a smaller shift of the offset and therefore to a smaller TC.sub.Off.

[0096] Generally, the proposed principle also works for the case that the bridge 130 is supplied with a constant supply voltage V.sub.DD or that the TC.sub.SB_TMR is positive. In the latter case, the resistance temperature coefficient of the implemented series resistor must also have the opposite sign.

[0097] In general, there is a plurality of possibilities for the arrangement of the series or parallel resistors in the bridge circuit, in order to achieve the temperature compensation of sensitivity and offset. A combination of the example implementations described with reference to FIG. 3 and FIG. 11 is illustrated in FIG. 13, wherein the parallel-connected compensating resistor R.sub.comp is labeled with reference sign 140 and the series compensating resistor R.sub.2,series connected in the half bridge R.sub.1, R.sub.2 is labeled with reference sign 140. Also, the example implementations described with reference to FIG. 8 and FIG. 11 can be combined with one another, so that a series circuit with a constant-voltage source, a ground connection 120 and a bridge circuit 130 is created, comprising at least one half bridge with a first and a second xMR resistor, which have a negative temperature coefficient in each case. The combined sensor circuit comprises at least one compensating resistor 140 with negative temperature coefficient which is less than the temperature coefficient of the first or second xMR resistor. The compensating resistor 140 is connected between the constant-voltage source and the bridge circuit 130 and the bridge circuit 130 is connected between the compensating resistor (140) and the ground connection. Alternatively, the compensating resistor 140 is connected between the bridge circuit 130 and the ground connection 120 and the bridge circuit 130 is connected between the constant-voltage source and the compensating resistor 140. A further compensating resistor R.sub.2,series is connected inside the half bridge (R.sub.1, R.sub.2) in series to the first and second xMR resistors R.sub.1, R.sub.2. The combined sensor circuit additionally has a second parallel half bridge (R.sub.3, R.sub.3) between the compensating resistor 140 and the ground connection 120.

[0098] Two further examples are shown in FIG. 14. In the circuit on the left, each bridge resistor R.sub.11 to R.sub.22 has a respectively allocated series compensating resistor. In the circuit on the right, each bridge resistor R.sub.11 to R.sub.22 has a respectively allocated parallel compensating resistor.

[0099] In semiconductor components, resistors with a positive temperature coefficient can be realized using materials such as metal or highly doped (poly) silicon. Resistors with a negative temperature coefficient can for example be achieved using less doped (poly) silicon.

[0100] The proposed sensor circuits having compensating resistors can achieve a more stable characteristic for the temperature without the costs and the additional space that would be required for active temperature compensation.

[0101] The aspects and features described in connection with a particular one of the previous examples may also be combined with one or more of the other examples to replace an identical or similar feature of this other example or to introduce the feature additionally into the other example.

[0102] Furthermore, it goes without saying that the disclosure of multiple steps, processes, operations or functions disclosed in the description or claims should not be interpreted as necessarily being in the described order, unless this is explicitly stated in the individual case or is mandatory for technical reasons. Therefore, the previous description does not restrict the execution of multiple steps or functions to a specific order. Furthermore, in other examples, a single step, a single function, a single process or a single operation may include and/or be broken into multiple substeps, subfunctions, subprocesses or suboperations.

[0103] If some aspects have been described in the preceding sections in connection with a device or system, these aspects are also to be understood as a description of the corresponding method. In this case, for example, a block, a device or a functional aspect of the device or the system may correspond to a feature, such as a method step, of the corresponding method. Correspondingly, aspects described in connection with a method are also to be understood as a description of a corresponding block, a corresponding element, a property or a functional feature of a corresponding device or of a corresponding system.

[0104] The following claims are hereby incorporated into the detailed description, each claim being independent as a separate example. It should also be noted thatalthough a dependent claim in the claims refers to a particular combination with one or more other claimsother examples may also comprise a combination of the dependent claim with the subject matter of any other dependent or independent claim. Such combinations are hereby explicitly proposed, unless it is stated in the individual case that a particular combination is not intended. Furthermore, features of a claim should also be included for any other independent claim, even if that claim is not directly defined as dependent on that other independent claim.