Oscillator circuits, current sources and methods for providing periodic frequency signals

Abstract

An oscillator circuit includes a temperature- and mechanically stress-compensated current source configured to provide a first electrical current. The oscillator circuit further includes a switched capacitor configured to provide a second electrical current. The oscillator circuit further includes an integrator configured to perform an integration based on a difference between the first electrical current and the second electrical current and to provide an integration signal based on the integration. The oscillator circuit further includes an oscillator configured to provide an output frequency signal, wherein the output frequency signal is controlled based on the integration signal provided by the integrator.The second electrical current provided by the switched capacitor is controlled in a feedback loop based on the output frequency signal of the oscillator.

Description

Technical area

[0001] The present disclosure relates to oscillator circuits, current sources and methods for providing periodic frequency signals. background

[0002] Oscillator circuits can suffer from mechanical stress, which can occur in various scenarios, such as during packaging of the oscillator, when soldering the packaged oscillator to a circuit board, or when moisture is present in the oscillator packaging. As a result of the mechanical stress, the oscillator frequency can change by up to two percent over the lifetime of the oscillator.

[0003] Manufacturers and designers of oscillator circuits are constantly striving to improve their products. In general, it may be desirable to provide highly stable and precise oscillators, preferably throughout their entire lifetime. In particular, it may be desirable to develop oscillator circuits with mechanical stress compensation to reduce lifetime drift effects. Summary

[0004] One aspect of the present disclosure relates to an oscillator circuit. The oscillator circuit includes a temperature- and mechanical stress-compensated current source configured to provide a first electrical current. The oscillator circuit further includes a switched capacitor configured to provide a second electrical current. The oscillator circuit further includes an integrator configured to perform an integration based on a difference between the first electrical current and the second electrical current and to provide an integration signal based on the integration. The oscillator circuit further includes an oscillator configured to provide an output frequency signal, wherein the output frequency signal is controlled based on the integration signal provided by the integrator.The second electrical current provided by the switched capacitor is controlled in a feedback loop based on the output frequency signal of the oscillator.

[0005] Another aspect of the present disclosure relates to an oscillator circuit. The oscillator circuit includes a PTAT voltage source configured to provide a voltage proportional to absolute temperature (VPTAT). The oscillator circuit further includes a reference voltage source configured to provide a reference voltage. The oscillator circuit further includes an RC element comprising a switched capacitor and a silicided and / or metal resistor. The oscillator circuit further includes an integrator, wherein a first input of the integrator is configured to receive a first input signal based on the reference voltage and an output voltage of the RC element, and a second input of the integrator is configured to receive a second input signal based on the VPTAT.The integrator is configured to perform an integration based on a difference or sum of the first input signal and the second input signal and to provide an integration signal based on the integration. The oscillator circuit further comprises an oscillator configured to provide an output frequency signal, wherein the output frequency signal is controlled based on the integration signal provided by the integrator. The switched capacitor is controlled in a feedback loop based on the output frequency signal of the oscillator.

[0006] Another aspect of the present disclosure relates to a current source configured to provide a temperature- and mechanical stress-compensated electrical current. The current source includes a PTAT voltage source configured to provide a voltage proportional to absolute temperature (VPTAT), wherein the PTAT voltage source includes a silicided polysilicon resistor and / or metal resistor.

[0007] Another aspect of the present disclosure relates to a method for providing a periodic frequency signal. The method includes a process of providing a first electrical current using a temperature- and mechanical stress-compensated current source. The method further includes a process of providing a second electrical current using a switched capacitor. The method further includes a process of performing an integration based on a difference between the first electrical current and the second electrical current using an integrator, thereby providing an integration signal based on the integration. The method further includes a process of controlling an output frequency signal provided by an oscillator based on the integration signal.The method further includes an operation of controlling the second electrical current provided by the switched capacitor based on the output frequency signal provided by the oscillator. Short description of the drawings

[0008] Devices and methods according to the disclosure are described in more detail below based on the drawings. Similar reference numerals may designate correspondingly similar parts. The technical features of the various illustrated examples may be combined, provided they are not mutually exclusive, and / or may be selectively omitted if not described as necessarily required. Fig. 1 illustrates a schematic diagram of a power source 100 according to the disclosure. Fig. 2 illustrates a schematic diagram of a power source 200 according to the disclosure. Fig. 3 illustrates a schematic diagram of an oscillator circuit 300 according to the disclosure. Fig. 4 illustrates a schematic diagram of an oscillator circuit 400 according to the disclosure. Fig. 5 illustrates a schematic diagram of an oscillator circuit 500 according to the disclosure. Fig. 6 illustrates a schematic diagram of an oscillator circuit 600 according to the disclosure. Fig. 7 illustrates a schematic diagram of an oscillator circuit 700 according to the disclosure. Fig. 8 illustrates a flowchart of a method for providing a periodic frequency signal according to the disclosure. Detailed description

[0009] Current sources according to the disclosure may be configured to provide a temperature- and mechanically stress-compensated electrical current. The current sources may include a PTAT voltage source configured to provide a voltage proportional to absolute temperature (VPTAT), wherein the PTAT voltage source may include a silicided resistor and / or metal resistor. In particular, the silicided resistor may be a silicided polysilicon resistor.

[0010] With reference to Fig. 1, an exemplary current source 100 may include two transistors 2A, 2B, a resistor 4, an amplifier 6, three transistors 8A through 8C, and a capacitor 10. In the illustrated example, the two transistors 2A and 2B may be bipolar transistors of different sizes, and the amplifier 6 may correspond to an operational transconductance amplifier (OTA). The resistor 4 may include or correspond to a silicided resistor and / or metal resistor. In particular, the silicided resistor may be a silicided polysilicon resistor (or a silicided poly resistor). In the illustrated example, the silicided resistor and / or metal resistor 4 may form an L-shaped resistor. The components of the current source 100 may be powered by a supply voltage VDD.

[0011] The current source 100 may include a bandgap reference circuit with a first current path on the left side, which includes the first bipolar transistor 2A, and a second current path on the right side, which includes the second bipolar transistor 2B. The silicided resistor and / or metal resistor 4 may be connected in series with the second bipolar transistor 2B. During operation, the transistors 8A, 8B and the OTA 6 may ensure that an electrical potential V A equal to an electrical potential V Band that electrical currents through the first and second current paths are equal. In the bandgap reference circuit, a voltage proportional to the absolute temperature Vptat can be generated. Accordingly, the current source 100 can be configured to generate a current proportional to the absolute temperature (IPTAT). That is, the current source 100 can correspond to a PTAT current source that includes the described bandgap reference circuit. The electrical current Iptat can depend on the generated voltage Vptat and the resistance value Rsilicided of the silicided resistor and / or metal resistor 4, i.e., Iptat-Vptat / Rsilicided.

[0012] A value of the electric current Iptat may depend on a first temperature coefficient resulting from the voltage Vptat. In particular, the voltage Vptat may increase proportionally to temperature. In addition, a value Rsilicided of the silicided resistor and / or metal resistor 4 may depend on a second temperature coefficient. In one non-limiting example, each of the first and second temperature coefficients may be in a range from about 3100 ppm / K to about 3350 ppm / K. In particular, the values ​​of the two temperature coefficients may match up to about 90 percent, or up to about 95 percent, or up to about 98 percent. As a result, a temperature dependence of the electric current Iptat may cancel out, so that the electric current provided by the current source 100 may be temperature compensated.

[0013] The silicided resistor and / or metal resistor 4 may be substantially insensitive to mechanical stress. In general, metal resistors may be substantially independent of mechanical stress compared to polysilicon resistors or diffused resistors. Silicided resistors may have metallic properties on their surfaces and may thus respond to mechanical stress in a similar manner. In particular, a silicided resistor of the current source 100 may be a silicided polysilicon resistor, which, unlike silicided diffusion resistors, does not necessarily suffer from leakage effects at high temperatures. In the illustrated example, the L-shaped silicided resistor and / or metal resistor 4 may include first and second resistors connected in series and arranged substantially perpendicular to each other.Each of the two resistors can be a silicided resistor or a metal resistor. The perpendicular arrangement of the two resistors can accommodate mechanical stress in both directions, so the use of the L-shaped resistor 4 can be independent of the direction. Due to the described mechanical stress independence of the silicided resistor and / or metal resistor 4, the electrical current provided by the current source 100 can be stress-compensated.

[0014] Due to the described use of the silicided resistor and / or metal resistor 4, the current source 100 may represent a temperature- and mechanically stress-compensated current source configured to provide a (substantially) constant electrical current. In contrast, conventional current sources using polysilicon resistors and / or diffused resistors may suffer from temperature changes and mechanical stress applied to the current source. For example, mechanical stress may occur during packaging of the oscillator circuit, during soldering of the packaged oscillator circuit to a printed circuit board, when moisture is present in the oscillator packaging, or the like.

[0015] With reference to Fig. 2, a power source 200 is illustrated which incorporates some or all of the features of the power source 100 of Fig. 1. The power source 200 can be seen as an extension of the power source 100. The power source 200 can include a temperature and mechanical stress compensated power source 200A configured to provide a first electrical current. For example, the power source 200A can be similar to the power source 100 of Fig. 1. The first electric current Iconst_silicided can thus be essentially independent of temperature changes and mechanical stress, as previously described in connection with Fig. 1. The first electric current Iconst_silicided may depend on the voltage Vptat and the resistance value Rsilicided of the silicided resistor and / or metal resistor 4, i.e., Iptat-Vptat / Rsilicided.

[0016] Current source 200 may further include a constant voltage source 200B configured to generate a substantially constant voltage Vconst. Voltage source 200B may include similar components as current source 200A. A voltage source 12 configured to provide a constant voltage may be arranged in a left current path, while a resistor 14 may be arranged in a right current path. For example, constant voltage source 12 may be substantially independent of temperature changes, i.e., an associated temperature coefficient may have a value of approximately 0 ppm / K.

[0017] Resistor 14 may include or correspond to a non-silicided polysilicon resistor. In one non-limiting example, non-silicided polysilicon resistor 14 may depend on a temperature coefficient in a range from about 0 ppm / K to about 200 ppm / K. A generated second electrical current Iconst_ non _silicided can be mirrored and output by the third transistor 8C. The second electrical current Iconst_ non_ silicided can be controlled by the constant voltage Vconst and a resistance value Rpoly _non_ silicided of the non-silicided polysilicon resistor 14, ie Iconst _non_ Silicided~Vconst / Rpoly _non_ Silicided.

[0018] An electric current Iconst output from the current source 200 may be based on the first electric current Iconst_silicided and the second electric current Iconst _non_silicided. In this context, the current source 200 may include a weighting unit 16 configured to generate the second electrical current Iconst _non_ silicided with a weighting factor b. In addition, the current source 200 may include an adder and / or subtractor 18 configured to output a sum or a difference of two input signals. In the illustrated example, the electrical current Iconst output by the current source 200 may be derived from a summation of the first electrical current Iconst_silicided and the second electrical current Iconst_ non _silicided, weighted by the weighting factor b. Alternatively, the electrical current Iconst provided by the current source 200 may depend on a subtraction of the second electrical current Iconst_ non_silicided, weighted by the weighting factor b, depend on the first electric current Iconst_silicided.

[0019] The weighting factor b can be adjusted to reduce a mechanical stress dependence of the supplied electrical current Iconst. The silicided resistor / metal resistor 4 can depend on a first piezoresistive coefficient S1, while the non-silicided polysilicon resistor 14 can depend on a second piezoresistive coefficient S2. A mechanical stress dependence can be reduced if a piezoresistive coefficient S=S1+b⋅S21+b is adjusted to have a value of substantially zero. In a non-limiting example, the piezoresistive coefficients S1 and S2 may have values ​​of about 1.5% / GPa and about 4.9% / GPa, respectively. In such a case, the weighting factor b may be adjusted to have a value of about 0.31 (or about -0.31) so that the value of S may be substantially equal to zero. Compared to the example of Fig. 1, the current source 200 can use the additional resistor 14 to achieve additional compensation of the mechanical stress dependence. The current source 200 can thus be considered as an extension of the current source 100 of Fig. 1 can be seen.

[0020] With reference to Fig. 3 illustrates a schematic diagram of an oscillator circuit 300 according to the disclosure. Oscillator circuits as described herein may, in particular, correspond to on-chip oscillators. The oscillator circuit 300 may include a temperature- and mechanically stress-compensated current source 100 (see Vptat / Rsilicided) configured to provide a first electrical current Iin+. For example, the current source 100 may be Fig. 3 similar to one of the power sources 100 and 200 of Fig. 1 and Fig. 2. The oscillator circuit 300 may further include a switched capacitor 20 configured to provide a second electrical current Iin-. An integrator 22 of the oscillator circuit 300 may be configured to perform an integration based on a difference between the first electrical current Iin+ and the second electrical current Iin- and to provide an integration signal 24 based on the integration. The oscillator circuit 300 may further include an oscillator 26 configured to provide an output frequency signal 28 of an output frequency fout. The output frequency signal 28 may be controlled based on the integration signal 24 provided by the integrator 22. The second electrical current Iin- provided by the switched capacitor 20 may be controlled in a feedback loop based on the output frequency signal 28 of the oscillator 26.

[0021] In the illustrated example, the oscillator circuit 300 may include a frequency divider 30 configured to provide a switching frequency signal 32 of a switching frequency fsw based on the output frequency signal 28 provided by the oscillator 26. In particular, the frequency divider 30 may be configured to divide an input signal Clk by a division factor div. The switching frequency signal 32 may be configured to control the second electrical current Iin- provided by the switched capacitor 20. The oscillator circuit 300 may further include a reference voltage source 34 configured to provide a reference voltage Vref. A first input (+) of the integrator 22 may be electrically coupled to the compensated current source 100 and the switched capacitor 20, and a second input (-) of the integrator 22 may be electrically coupled to the reference voltage source 34.

[0022] During operation, the current source 100 may generate the substantially constant first electrical current Iin+ using a silicided resistor and / or metal resistor, as described in connection with Fig. 1 and Fig. 2. The switched capacitor 20 can generate the opposite second electrical current Iin-. The difference between the two electrical currents Iin+ and Iin can be integrated by the integrator 22, and the resulting integration signal 24 can control the oscillator 26. For example, the oscillator 26 can correspond to one of a voltage-controlled oscillator (VCO), a current-controlled oscillator (ICO), or a digitally controlled oscillator (DCO). Depending on the oscillator type, the integration signal 24 can correspond to one of an output voltage Vout, an electrical output current Iout, or a digital output signal D outThe output frequency signal 28 of the oscillator 26 can control the electrical current Iin- generated by the switched capacitor 20 in the feedback loop. In one non-limiting example, the output frequency fout can have a value of about 80 MHz or about 100 MHz, but can vary in other examples.

[0023] With reference to Fig. 4, an oscillator circuit 400 may include some or all of the features of the oscillator circuit 300 of Fig. 3. The oscillator circuit 400 can be viewed as a more detailed version of the oscillator circuit 300. An integrator of the oscillator circuit 400 can include an OTA 36, a capacitor 38, and a resistor 40. The integrator can be a Gm-C integrator. An oscillator 26 of the oscillator circuit 400 can include or correspond to a ring oscillator or a relaxation-type oscillator. In the illustrated example, the oscillator 26 can be a ring oscillator that includes an odd number (here: three) of inverters forming an inverter chain. The oscillator circuit 400 can further include a current source 42 electrically coupled to the output of the OTA 36 and the input of the oscillator 26. An output current provided by the current source 42 can be controlled based on the integration signal of the integrator.The output current of current source 42 may be configured to control the output frequency fout of oscillator 26. In other examples, oscillator circuit 400 may include a voltage source controlled by the integration signal and configured to provide an output voltage for controlling the output frequency fout of oscillator 26.

[0024] The switched capacitor 20 may be substantially independent of mechanical stress. In a first switching state, the switch may be in an upper position, and the capacitor 20 may be charged by the electrical current Iin+ provided by the power source 100. In a second switching state, the switch may be in a lower position, and the capacitor 20 may be discharged. That is, during operation, the electrical current Iin+ may charge the switched capacitor 20, but switching the capacitor 20 at the switching frequency fsw may also cause the switched capacitor 20 to periodically discharge. Such constant charging and discharging of the switched capacitor 20 may generate the opposite electrical current Iin provided by the switched capacitor 20.In particular, the generated opposite electric current Iin- can be proportional to the switching frequency fsw of the switched capacitor 20. The higher the switching frequency fsw, the higher the generated electric current Iin- can be. Due to the loop nature of the circuit, the frequency-dependent opposite electric current Iin- can be regulated to the electric current Iin+ provided by the current source 100. Consequently, in a balanced state, an average voltage of the capacitor 20 can match the constant reference voltage Vref. One goal of the oscillator circuit 400 can thus be seen as regulating the average voltage of the capacitor 20 in the loop so that it matches the reference voltage Vref.

[0025] If the average voltage of capacitor 20 deviates from the reference voltage Vref, a voltage difference may be applied to the inputs of OTA 36. OTA 36 may then act as a voltage-to-current converter and may output an electrical current signal 46 dependent on the applied voltage difference. The electrical current signal 46 output by OTA 36 may charge capacitor 38 and may be integrated by the integrator. In this context, resistor 40 may be configured to provide dynamic compensation. A voltage developing across capacitor 38 may be proportional to an integral of the charging current 46 over time. The integrated current may be converted into a voltage signal 48 that controls current source 42. An output signal of current source 42 may control oscillator 26, which in this case may be a current-controlled oscillator (ICO).Furthermore, the output frequency signal 28 provided by the oscillator 26 can control the switching frequency fsw of the switched capacitor 20. The control loop allows the oscillator 26 to settle into a balanced state so that a constant output frequency fout can be provided.

[0026] Frequency divider 30 may be considered optional in some examples. Frequency divider 30 may be configured to divide the frequency fout of output frequency signal 28 by a factor div. In one non-limiting example, factor div may have a value of 10, 16, or 32. By switching capacitor 20 with a reduced switching frequency fsw, dynamic effects (such as parasitic capacitances) may be reduced or negligible, so that operating accuracy of oscillator circuit 400 may be improved.

[0027] With reference to Fig. 5, an oscillator circuit 500 may include some or all of the features of previously described oscillator circuits. The oscillator circuit 500 may include an operational amplifier integrator having an operational amplifier 50, a capacitor 38, and a resistor 40. Similar to the example of Fig. 4, when the average voltage of the switched capacitor 20 deviates from the reference voltage Vref, a voltage difference can be applied to the inputs of the operational amplifier 50. The integrator can integrate the applied voltage difference, and based on this, the operational amplifier 50 can output an integration signal 24 in the form of a voltage signal. The voltage signal can control the oscillator 26, which in this case can be a voltage-controlled oscillator (VCO).

[0028] With reference to Fig. 6, an oscillator circuit 600 may include some or all of the features of previously described oscillator circuits. The oscillator circuit 600 may include a comparator 52 and a downstream digital integrator 54. Similar to the previous examples, when the average voltage of the switched capacitor 20 deviates from the reference voltage Vref, a voltage difference may be applied to the inputs of the comparator 52. The digital integrator 54 may perform an integration based on an output signal of the comparator 52. Based on the performed integration, the digital integrator 54 may output a signal to control the current source 42. An output signal of the current source 42 may control the oscillator 26, which in this case may be a current-controlled oscillator (ICO).

[0029] With reference to Fig. 7 illustrates another oscillator circuit 700 according to the disclosure, which may include some or all of the features of previously described oscillator circuits. The oscillator circuit 700 may include a PTAT voltage source 56 configured to provide a voltage Vptat proportional to absolute temperature. Additionally, a reference voltage source 58 may be configured to provide a reference voltage Vref2. An RC element of the oscillator circuit 700 may include a switched capacitor 20 and a silicided and / or metal resistor 4. The oscillator circuit 700 may further include an integrator, which in the illustrated example may include an OTA 36, a capacitor 38, and a resistor 40. A first input of the OTA 36 may be configured to receive a first input signal based on the reference voltage Vref2 and an output voltage of the RC element.A second input of the OTA 36 may be configured to receive a second input signal based on the voltage Vptat. The integrator may be configured to perform an integration based on a difference or sum of the first input signal and the second input signal and to provide an integration signal based on the integration. The oscillator circuit 700 may further include an oscillator 26 configured to provide an output frequency signal 28, wherein the output frequency signal 28 may be controlled based on the integration signal provided by the integrator. The switched capacitor 20 may be controlled in a feedback loop based on the output frequency signal 28 of the oscillator 26.

[0030] In the illustrated example, a silicided and / or metal resistor 4 may be used in the RC element, in contrast to previous examples in which a silicided and / or metal resistor was used in a current source. It should be noted that the integrator of Fig. 7 similar to that in connection with Fig. 4. Similar to the previous examples, the control loop of the circuit may allow the oscillator 26 to settle into a balanced state so that a constant output frequency fout can be provided.

[0031] The oscillator circuits described above may include additional components that are not illustrated for simplicity. For example, an oscillator circuit according to the disclosure may include at least one of a temperature sensor or a mechanical stress sensor. The temperature sensor may be configured to provide a first sensor signal representative of a temperature of the oscillator circuit. The mechanical stress sensor may be configured to provide a second sensor signal representative of a mechanical stress in the silicided resistor and / or metal resistor 4.Additionally, an oscillator circuit may include a (digital or analog) processing unit configured to adjust at least one of the reference voltage Vref, the voltage Vptat, the division factor div of the frequency divider 30, or the switched capacitor 20 based on at least one of the first sensor signal or the second sensor signal. The described adjustment, performed by the processing unit and based on the provided sensor signals, may enable digitally assisted compensation of residual and higher-order mechanical stress and temperature effects.

[0032] With reference to Fig. Figure 8 illustrates a flowchart of a method according to the disclosure for providing a periodic frequency signal. The method is described in a general manner to qualitatively specify aspects of the disclosure. For example, the method may be performed by one of the oscillator circuits described above. It is understood that the method may include further aspects. For example, the method may be extended by one of the aspects discussed in connection with other examples described herein.

[0033] At 60, a first electrical current may be provided using a temperature and mechanical stress compensated current source. At 62, a second electrical current may be provided using a switched capacitor. At 64, integration based on a difference between the first electrical current and the second electrical current may be performed using an integrator. An integration signal may be provided based on the integration. At 66, an output frequency signal provided by an oscillator may be controlled based on the integration signal. At 68, the second electrical current provided by the switched capacitor may be controlled based on the output frequency signal provided by the oscillator.

[0034] The procedure from Fig. 8 may include one or more further steps, which may be considered optional. For example, with reference to the frequency divider 30 of the previous examples, a switching frequency signal may be provided by the frequency divider based on the output frequency signal provided by the oscillator. In yet another step, the second electrical current provided by the switched capacitor may be controlled based on the switching frequency signal.

[0035] Oscillator circuits according to the disclosure can provide the following exemplary technical effects and, based thereon, can outperform conventional devices in various aspects.

[0036] The current sources of the oscillator circuits described herein may be subject to analog pre-compensation of mechanical stress and temperature effects, as described in connection with the examples of Fig. 1 and Fig.2, temperature and mechanical stress compensation can be provided. Additionally, digitally assisted compensation of residual and higher-order mechanical stress and temperature effects can be provided. As a result, the oscillator circuits described herein can provide high and stable output frequencies. The oscillator circuits can provide high stability against temperature, lifetime, and aging effects caused by mechanical and, to some extent, electrical stress.

[0037] Conventional oscillator circuits, such as relaxation-type oscillators, can suffer from delay effects (and associated aging effects) caused by the use of a comparator. Such delay effects can drift over the lifetime, e.g., caused by mechanical stress. In oscillator circuits using comparators, the delay effects can typically affect the target frequency by about 0.5-3%. Oscillator circuits according to the disclosure can be free of the mentioned delay effects. The delay effects can be reduced to virtually 0%. Any remaining delay effects in the overall circuit are also considered only as a second approximation and are in any case less than about 0.1%.

[0038] The oscillator circuits described herein can provide high output frequencies with low power consumption. Additionally, the concepts discussed can enable low power consumption with additional duty cycle operation to further reduce power consumption. In non-limiting examples, the oscillator circuits described herein can be used for high-speed sensor interfaces, low-power battery-operated IoT sensor nodes, high-speed inductive angle sensors, or the like. Examples

[0039] Oscillator circuits, current sources and methods for providing periodic frequency signals according to the disclosure are described below by way of examples.

[0040] Example 1 is an oscillator circuit comprising: a temperature and mechanical stress compensated current source configured to provide a first electrical current; a switched capacitor configured to provide a second electrical current; an integrator configured to perform integration based on a difference between the first electrical current and the second electrical current and to provide an integration signal based on the integration; and an oscillator configured to provide an output frequency signal, wherein the output frequency signal is controlled based on the integration signal provided by the integrator, wherein the second electrical current provided by the switched capacitor is controlled in a feedback loop based on the output frequency signal of the oscillator.

[0041] Example 2 is an oscillator circuit according to Example 1, wherein the compensated current source comprises a PTAT voltage source configured to provide a voltage proportional to absolute temperature (VPTAT), wherein the PTAT voltage source comprises a silicided resistor and / or metal resistor.

[0042] Example 3 is an oscillator circuit according to Example 2, wherein the compensated current source comprises a PTAT current source configured to provide a current proportional to absolute temperature (IPTAT), wherein the PTAT current source comprises a bandgap reference circuit.

[0043] Example 4 is an oscillator circuit according to Example 3, wherein: a value of the IPTAT depends on a first temperature coefficient based on the VPTAT, a value of the silicided resistor and / or metal resistor depends on a second temperature coefficient, and the first temperature coefficient substantially matches the second temperature coefficient.

[0044] Example 5 is an oscillator circuit according to any one of Examples 2 to 4, wherein the silicided resistor and / or metal resistor forms an L-shaped resistor.

[0045] Example 6 is an oscillator circuit according to any one of the preceding examples, further comprising: a frequency divider configured to provide a switching frequency signal based on the output frequency signal provided by the oscillator, wherein the switching frequency signal is configured to control the second electrical current provided by the switched capacitor.

[0046] Example 7 is an oscillator circuit according to any one of the preceding examples, further comprising: a reference voltage source configured to provide a reference voltage, wherein a first input of the integrator is electrically coupled to the compensated current source and the switched capacitor, and a second input of the integrator is electrically coupled to the reference voltage source.

[0047] Example 8 is an oscillator circuit according to any one of the preceding examples, wherein the oscillator comprises a ring oscillator or a relaxation-type oscillator.

[0048] Example 9 is an oscillator circuit according to any one of Examples 2 to 8, wherein the compensated current source further comprises a constant voltage source configured to provide a substantially constant voltage, the constant voltage source comprising a non-silicided polysilicon resistor.

[0049] Example 10 is an oscillator circuit according to Example 9, wherein: the electrical current provided by the compensated current source is generated based on a first electrical current and a second electrical current, the first electrical current depends on the VPTAT and the value of the silicided resistor and / or metal resistor, and the second electrical current depends on the constant voltage and the value of the non-silicided polysilicon resistor.

[0050] Example 11 is an oscillator circuit according to Example 10, wherein: the electrical current provided by the compensated current source depends on a subtraction or summation of the second electrical current, weighted by a weighting factor, and the first electrical current, and the weighting factor is adjusted to reduce a mechanical stress dependence of the electrical current provided by the compensated current source.

[0051] Example 12 is an oscillator circuit according to any one of the preceding examples, further comprising: at least one of a temperature sensor or a mechanical stress sensor, wherein the temperature sensor is configured to provide a first sensor signal representative of a temperature of the oscillator circuit, wherein the mechanical stress sensor is configured to provide a second sensor signal representative of a mechanical stress in the silicided resistor and / or metal resistor, and a processing unit configured to adjust at least one of the reference voltage, the VPTAT, a division factor of the frequency divider, or the switched capacitor based on at least one of the first sensor signal or the second sensor signal.

[0052] Example 13 is an oscillator circuit according to any one of the preceding examples, further comprising: a further voltage source or current source, wherein an output voltage or output current provided by the further voltage source or current source is controlled based on the integration signal of the integrator, wherein the output voltage or output current is configured to control the output frequency of the oscillator.

[0053] Example 14 is an oscillator circuit according to Example 13, wherein the integrator comprises an operational transconductance amplifier electrically coupled to the further voltage source or current source.

[0054] Example 15 is an oscillator circuit according to Example 13, wherein the integrator comprises a digital integrator electrically coupled to the further voltage source or current source.

[0055] Example 16 is an oscillator circuit comprising: a PTAT voltage source configured to provide a voltage proportional to absolute temperature (VPTAT); a reference voltage source configured to provide a reference voltage; an RC element comprising a switched capacitor and a silicided and / or metal resistor; an integrator, wherein a first input of the integrator is configured to receive a first input signal based on the reference voltage and an output voltage of the RC element, and a second input of the integrator is configured to receive a second input signal based on the VPTAT, wherein the integrator is configured to perform an integration based on a difference or sum of the first input signal and the second input signal and to provide an integration signal based on the integration;and an oscillator configured to provide an output frequency signal, wherein the output frequency signal is controlled based on the integration signal provided by the integrator, wherein the switched capacitor is controlled in a feedback loop based on the output frequency signal of the oscillator;

[0056] Example 17 is a current source configured to provide a temperature and mechanical stress compensated electrical current, the current source comprising: a PTAT voltage source configured to provide a voltage proportional to absolute temperature (VPTAT), the PTAT voltage source comprising a silicided polysilicon resistor and / or metal resistor.

[0057] Example 18 is a current source according to Example 17, wherein: a value of the VPTAT depends on a first temperature coefficient, a value of the silicided polysilicon resistor and / or metal resistor depends on a second temperature coefficient, and the first temperature coefficient substantially matches the second temperature coefficient.

[0058] Example 19 is a method for providing a periodic frequency signal, the method comprising: providing a first electrical current using a temperature and mechanical stress compensated current source; providing a second electrical current using a switched capacitor; performing an integration based on a difference of the first electrical current and the second electrical current using an integrator, thereby providing an integration signal based on the integration; controlling an output frequency signal provided by an oscillator based on the integration signal; and controlling the second electrical current provided by the switched capacitor based on the output frequency signal provided by the oscillator.

[0059] Example 20 is a method according to Example 19, further comprising: providing a switching frequency signal based on the output frequency signal using a frequency divider, and controlling the second electrical current provided by the switched capacitor based on the switching frequency signal.

[0060] Although the present disclosure has been described with reference to illustrative examples, this description is not intended to be construed in a limiting sense. Various modifications and combinations of the illustrative examples, as well as other examples of the disclosure, will become apparent to those skilled in the art upon reference to the description. It is therefore intended that the appended claims encompass such modifications or examples.

Claims

[1] Oscillator circuit comprising: a temperature and mechanical stress compensated current source (100, 200) configured to provide a first electrical current; a switched capacitor (20) configured to provide a second electrical current; an integrator (22) configured to perform an integration based on a difference between the first electrical current and the second electrical current and to provide an integration signal (24) based on the integration; and an oscillator (26) configured to provide an output frequency signal (28), wherein the output frequency signal (28) is controlled based on the integration signal (24) provided by the integrator (22), wherein the second electrical current provided by the switched capacitor (20) is controlled in a feedback loop based on the output frequency signal (28) of the oscillator (26). [2] The oscillator circuit of claim 1, wherein the compensated current source (100, 200) comprises a PTAT voltage source configured to provide a voltage proportional to absolute temperature (VPTAT), the PTAT voltage source comprising a silicided resistor and / or metal resistor (4). [3] The oscillator circuit of claim 2, wherein the compensated current source (100, 200) comprises a PTAT current source configured to provide a current proportional to absolute temperature (IPTAT), the PTAT current source comprising a bandgap reference circuit. [4] Oscillator circuit according to claim 3, wherein: a value of the IPTAT depends on a first temperature coefficient based on the VPTAT, a value of the silicided resistor and / or metal resistor (4) depends on a second temperature coefficient, and the first temperature coefficient is substantially the same as the second temperature coefficient. [5] Oscillator circuit according to one of claims 2 to 4, wherein the silicided resistor and / or metal resistor (4) forms an L-shaped resistor. [6] Oscillator circuit according to one of the preceding claims, further comprising: a frequency divider (30) configured to provide a switching frequency signal (32) based on the output frequency signal (28) provided by the oscillator (26), wherein the switching frequency signal (32) is configured to control the second electrical current provided by the switched capacitor (20). [7] Oscillator circuit according to one of the preceding claims, further comprising: a reference voltage source (34) configured to provide a reference voltage, wherein a first input of the integrator (22) is electrically coupled to the compensated current source (100, 200) and the switched capacitor (20) and a second input of the integrator (22) is electrically coupled to the reference voltage source (34). [8] Oscillator circuit according to one of the preceding claims, wherein the oscillator (26) comprises a ring oscillator or a relaxation type oscillator. [9] The oscillator circuit of any one of claims 2 to 8, wherein the compensated current source (100, 200) further comprises a constant voltage source configured to provide a substantially constant voltage, the constant voltage source comprising a non-silicided polysilicon resistor (14). [10] Oscillator circuit according to claim 9, wherein: the electric current provided by the compensated current source (100, 200) is generated based on a first electric current and a second electric current, the first electric current depends on the VPTAT and the value of the silicided resistor and / or metal resistor (4), and the second electric current depends on the constant voltage and the value of the non-silicided polysilicon resistor (14). [11] Oscillator circuit according to claim 10, wherein: the electrical current provided by the compensated current source (100, 200) depends on a subtraction or summation of the second electrical current, weighted by a weighting factor, and the first electrical current, and the weighting factor is adjusted to reduce a mechanical stress dependence of the electrical current provided by the compensated current source (100, 200). [12] Oscillator circuit according to one of the preceding claims, further comprising: at least one of a temperature sensor or a mechanical stress sensor, wherein the temperature sensor is configured to provide a first sensor signal representative of a temperature of the oscillator circuit, wherein the mechanical stress sensor is configured to provide a second sensor signal representative of a mechanical stress in the silicided resistor and / or metal resistor (4), and a processing unit configured to adjust at least one of the reference voltage, the VPTAT, a division factor of the frequency divider (30), or the switched capacitor (20) based on at least one of the first sensor signal or the second sensor signal. [13] Oscillator circuit according to one of the preceding claims, further comprising: a further voltage source or current source (42), wherein an output voltage or output current provided by the further voltage source or current source (42) is controlled based on the integration signal (24) of the integrator (22), wherein the output voltage or output current is configured to control the output frequency (28) of the oscillator (26). [14] Oscillator circuit according to claim 13, wherein the integrator (22) comprises an operational transconductance amplifier (36) electrically coupled to the further voltage source or current source (42). [15] Oscillator circuit according to claim 13, wherein the integrator (22) comprises a digital integrator (54) electrically coupled to the further voltage source or current source (42). [16] Oscillator circuit comprising: a PTAT voltage source (56) configured to provide a voltage proportional to absolute temperature (VPTAT); a reference voltage source (58) configured to provide a reference voltage; an RC element comprising a switched capacitor (20) and a silicided and / or metallic resistor (4); an integrator (22), wherein a first input of the integrator (22) is configured to receive a first input signal based on the reference voltage and an output voltage of the RC element, and a second input of the integrator (22) is configured to receive a second input signal based on the VPTAT, wherein the integrator (22) is configured to perform an integration based on a difference or sum of the first input signal and the second input signal and to provide an integration signal (24) based on the integration; and an oscillator (26) configured to provide an output frequency signal (28), wherein the output frequency signal (28) is controlled based on the integration signal (24) provided by the integrator (22), wherein the switched capacitor (20) is controlled in a feedback loop based on the output frequency signal (28) of the oscillator (26). [17] A power source (100, 200) configured to provide a temperature and mechanical stress compensated electrical current, the power source comprising: a PTAT voltage source configured to provide a voltage proportional to absolute temperature (VPTAT), wherein the PTAT voltage source comprises a silicided polysilicon resistor and / or metal resistor (4). [18] A power source according to claim 17, wherein: a value of the VPTAT depends on a first temperature coefficient, a value of the silicided polysilicon resistor and / or metal resistor (4) depends on a second temperature coefficient, and the first temperature coefficient is substantially the same as the second temperature coefficient. [19] A method for providing a periodic frequency signal, the method comprising: Providing a first electrical current using a temperature and mechanical stress compensated current source (100, 200); Providing a second electrical current using a switched capacitor (20); Performing an integration based on a difference of the first electric current and the second electric current using an integrator (22), thereby providing an integration signal (24) based on the integration; Controlling an output frequency signal (28) provided by an oscillator (26) based on the integration signal (24); and Controlling the second electrical current provided by the switched capacitor (20) based on the output frequency signal (28) provided by the oscillator (26). [20] The method of claim 19, further comprising: Providing a switching frequency signal (32) based on the output frequency signal (28) using a frequency divider (30), and Controlling the second electrical current provided by the switched capacitor (20) based on the switching frequency signal (32).

Images