Oscillator circuit, current source and method for providing periodic frequency signal

Abstract

The invention relates to an oscillator circuit, a current source and a method for providing a periodic frequency signal. An oscillator circuit includes a temperature and mechanical stress compensation current source configured to provide a first current. The oscillator circuit also includes a switched capacitor configured to provide a second current. The oscillator circuit also includes an integrator configured to perform integration based on a difference of the first current and the second current, and to provide an integrated signal based on the integration. The oscillator circuit also includes an oscillator configured to provide an output frequency signal, wherein the output frequency signal is controlled based on an integrated signal provided by the integrator. A second current provided by the switched capacitor is controlled in a feedback loop based on an output frequency signal of the oscillator.

Description

Technical Field

[0001] The present disclosure relates to an oscillator circuit, a current source, and a method for providing a periodic frequency signal. Background Art

[0002] Oscillator circuits can be subject to mechanical stresses that can occur in various scenarios, such as when packaging the oscillator, when soldering the packaged oscillator to a printed circuit board, or if moisture is present in the oscillator package. As a result of the mechanical stresses that occur, during the lifetime of the oscillator, the oscillator frequency can change by up to 2%.

[0003] Manufacturers and developers of oscillator circuits have been working to improve their products. Generally, it may be desirable to provide highly stable and accurate oscillators, preferably highly stable and accurate throughout their lifetime. More specifically, it is desirable to develop oscillator circuits with mechanical stress compensation to reduce lifetime drift effects. Summary of the Invention

[0004] One aspect of the present disclosure relates to an oscillator circuit. The oscillator circuit includes a temperature and mechanical stress compensation current source configured to provide a first current. The oscillator circuit further includes a switched capacitor configured to provide a second current. The oscillator circuit further includes an integrator configured to perform integration based on a difference between the first current and the second 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 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 including a switched capacitor and a silicided and / or metallic 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 integration based on a difference or sum between the first input signal and the second input signal 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 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 current. The current source includes a PTAT voltage source configured to provide a voltage proportional to absolute temperature (VPTAT), where the PTAT voltage source includes a polysilicon silicide resistor and / or a metal resistor.

[0007] Another aspect of the present disclosure relates to a method for providing a periodic frequency signal. The method includes the act of providing a first current using a temperature and mechanical stress compensated current source. The method further includes the act of providing a second current using a switched capacitor. The method further includes the act of performing integration using an integrator based on the difference between the first current and the second current, thereby providing an integration signal based on the integration. The method further includes the act of controlling an output frequency signal provided by an oscillator based on the integration signal. The method further includes the act of controlling the second current provided by the switched capacitor based on the output frequency signal provided by the oscillator. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] The devices and methods according to the present disclosure are described in more detail below based on the drawings. Similar reference numerals may represent corresponding similar parts. The technical features of the various illustrated examples may be combined as long as they are not mutually exclusive, and / or the technical features of the various illustrated examples may be selectively omitted if not described as essential.

[0009] Figure 1 A schematic diagram of a current source 100 according to the present disclosure is shown.

[0010] Figure 2 A schematic diagram of a current source 200 according to the present disclosure is shown.

[0011] Figure 3 A schematic diagram illustrating an oscillator circuit 300 according to the present disclosure.

[0012] Figure 4 A schematic diagram illustrating an oscillator circuit 400 according to the present disclosure.

[0013] Figure 5 A schematic diagram of an oscillator circuit 500 according to the present disclosure is shown.

[0014] Figure 6 A schematic diagram of an oscillator circuit 600 according to the present disclosure is shown.

[0015] Figure 7 A schematic diagram illustrating an oscillator circuit 700 according to the present disclosure.

[0016] Figure 8 A flowchart of a method for providing a periodic frequency signal according to the present disclosure is shown. DETAILED DESCRIPTION

[0017] A current source according to the present disclosure can be configured to provide temperature and mechanical stress compensated current. The current source can include a PTAT voltage source configured to provide a voltage proportional to absolute temperature (VPTAT), where the PTAT voltage source can include a silicided resistor and / or a metal resistor. In particular, the silicided resistor can be a silicided polysilicon resistor.

[0018] Now referring to Figure 1 , example current source 100 can include two transistors 2A, 2B, a resistor 4, an amplifier 6, three transistors 8A to 8C, and a capacitor 10. In the illustrated example, the two transistors 2A and 2B can be bipolar transistors of different sizes, and the amplifier 6 can correspond to an operational transconductance amplifier (OTA). The resistor 4 can include or can correspond to at least one of a silicided resistor or a metal resistor. In particular, the silicided resistor can be a silicided polysilicon resistor (or silicided polycrystalline resistor). In the illustrated example, the silicided resistor and / or the metal resistor 4 can form an L-shaped resistor. The components of the current source 100 can be powered by a supply voltage VDD.

[0019] The current source 100 can include a first bandgap reference circuit, the first current path on its left includes a first bipolar transistor 2A, and the second current path on its right includes a second bipolar transistor 2B. The silicided resistor and / or the metal resistor 4 can be connected in series with the second bipolar transistor 2B. During operation, transistors 8A, 8B, and OTA 6 can ensure that the potential V A is equal to the potential V B and the currents through the first and second current paths are equal. In the bandgap reference circuit, a voltage V ptat proportional to absolute temperature can be generated. Accordingly, the current source 100 can be configured to generate a current proportional to absolute temperature (IPTAT). That is, the current source 100 can correspond to a PTAT current source including a bandgap reference circuit. The current I ptat can depend on the generated voltage V ptat and the resistance value R silicided of the silicided resistor and / or the metal resistor 4, i.e., I ptat ~V ptat / R silicided .

[0020] The value of the current I ptat can depend on a first temperature coefficient caused by the voltage V ptat . In particular, the voltage V ptat can increase proportionally with temperature. In addition, the value R silicidedIt may depend on the second temperature coefficient. In a non-limiting example, each of the first and second temperature coefficients may be in the range of about 3100 ppm / K to about 3350 ppm / K. The first temperature coefficient caused by the voltage V ptat can be substantially matched to the second temperature coefficient of the silicided resistor and / or the metal resistor 4. More specifically, the values of the two temperature coefficients can be matched up to about 90%, or up to about 95%, or up to about 98%. As a result, the temperature dependence of the current I ptat can be cancelled out such that the current provided by the current source 100 can be temperature compensated.

[0021] The silicided resistor and / or the metal resistor 4 may be substantially insensitive to mechanical stress. Generally, compared with polysilicon resistors or diffused resistors, metal resistors may be substantially unaffected by mechanical stress. The silicided resistor may have metal characteristics on its surface and can thus respond to mechanical stress in a similar manner. In particular, the silicided resistor of the current source 100 can be a silicided polysilicon resistor, which, unlike a silicided diffused resistor, 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 a first and a second resistor 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 address mechanical stress in two directions such that the use of the L-shaped resistor 4 can be direction-independent. Due to the insensitivity of the described silicided resistor and / or metal resistor 4 to mechanical stress, the current provided by the current source 100 can be stress compensated.

[0022] Due to the use of the described silicided resistor and / or metal resistor 4, the current source 100 can represent a temperature and mechanical stress compensated current source configured to provide (substantially) constant current I const . In contrast, a conventional current source using a polysilicon resistor and / or a diffused resistor may suffer from temperature variations and mechanical stress applied to the current source. For example, when packaging an oscillator circuit, when soldering the packaged oscillator circuit to a printed circuit board, mechanical stress etc. may occur if moisture etc. is present in the oscillator package.

[0023] Now referring to Figure 2 , there is shown a current source 200 that may include some or all of the features of the current source 100 including Figure 1 . The current source 200 can be regarded as an extension of the current source 100. The current source 200 may include a temperature and mechanical stress compensated current source 200A configured to provide a first current I const_silicided . For example, the current source 200A can be similar to the current source 100 including Figure 1 . The first current I const_silicidedTherefore, it can be substantially unaffected by temperature variations and mechanical stresses, as described previously in connection with Figure 1 the first current I const_silicided can depend on the voltage V ptat and the resistance value R of the silicided resistor and / or the metal resistor 4 silicided , i.e., I ptat ~V ptat / R silicided .

[0024] The current source 200 can also include a constant voltage source 200B configured to generate a substantially constant voltage V const . The voltage source 200B can include components similar to those of the current source 200A. The voltage source 12 configured to provide a constant voltage can be arranged in the left current path, while the resistor 14 can be arranged in the right current path. For example, the constant voltage source 12 can be substantially unaffected by temperature variations, i.e., the associated temperature coefficient can have a value of approximately 0 ppm / K

[0025] The resistor 14 can include or can correspond to a non-silicided polysilicon resistor. In a non-limiting example, the non-silicided polysilicon resistor 14 can depend on a temperature coefficient in the range from approximately 0 ppm / K to approximately 200 ppm / K. The generated second current I const_non_silicided can be mirrored and output by the third transistor 8C. The second current I const_non_silicided can depend on the constant voltage V const and the resistance value R of the non-silicided polysilicon resistor 14 poly_non_silicided , i.e., I const_non_silicided ~V const / R poly_non_silicided .

[0026] The current I output by the current source 200 const can be generated based on the first current I const_silicided and the second current I const_non_silicided . In this context, the current source 200 can include a weighting unit 16 configured to receive the second current I const_non_silicided and weight the second current I const_non_silicided using a weighting factor b. Additionally, the current source 200 can include an adder and / or a subtractor 18 configured to output the sum or difference of two input signals. In the illustrated example, the current I output by the current source 200 const can depend on the sum of the first current I const_silicided and the second current I weighted by the weighting factor b const_non_silicided . Alternatively, the current I provided by the current source 200 const can depend on the subtraction of the second current I weighted by the weighting factor b from the first current I const_silicided ​const_non_silicided 。

[0027] The weighting factor b can be adjusted to reduce the provided current I const 's mechanical stress dependence. The silicide resistor / metal resistor 4 can depend on the first piezoresistive coefficient S1, while the polysilicide resistor 14 can depend on the second piezoresistive coefficient S2. If the piezoresistive coefficient S = is adjusted to have a value that is substantially zero, the mechanical stress dependence can be reduced. In a non-limiting example, the piezoresistive coefficients S1 and S2 can have values of approximately 1.5% / GPa and approximately 4.9% / GPa, respectively. In this case, the weighting factor b can be adjusted to have a value of approximately 0.31 (or approximately -0.31) such that the value of S can be substantially equal to zero. Compared with the example of Figure 1 , the current source 200 can use the additional resistor 14 to achieve additional compensation for the mechanical stress dependence. Thus, the current source 200 can be regarded as Figure 1 an extension of the current source 100.

[0028] Now referring to Figure 3 , a schematic diagram of an oscillator circuit 300 according to the present disclosure is shown. The oscillator circuit described herein can specifically correspond to an on-chip oscillator. The oscillator circuit 300 can include a temperature and mechanical stress compensation current source 100 configured to provide a first current I in +(see V ptat / R silicided ). For example, Figure 3 's current source 100 can be similar to one of the current sources 100 and 200 of Figure 1 and Figure 2 . The oscillator circuit 300 can further include a switched capacitor 20 configured to provide a second current I in -. The integrator 22 of the oscillator circuit 300 can be configured to perform integration based on the difference between the first current I in + and the second current I in -, and provide an integration signal 24 based on the integration. The oscillator circuit 300 can further include an oscillator 26 configured to provide an output frequency signal 28 of an output frequency f out . The output frequency signal 28 can be controlled based on the integration signal 24 provided by the integrator 22. The second current I in - provided by the switched capacitor 20 can be controlled in a feedback loop based on the output frequency signal 28 of the oscillator 26.

[0029] In the example shown, the oscillator circuit 300 can include a frequency divider 30 configured to provide a switching frequency f swThe switching frequency signal 32. In particular, the frequency divider 30 can be configured to divide the input signal Clk by a division factor div. The switching frequency signal 32 can be configured to control the second current I provided by the switched capacitor 20 in -. The oscillator circuit 300 can also include a reference voltage source 34 configured to provide a reference voltage V ref . The first input (+) of the integrator 22 can be electrically coupled to the compensation current source 100 and the switched capacitor 20, and the second input (-) of the integrator 22 can be electrically coupled to the reference voltage source 34

[0030] During operation, the current source 100 can generate a substantially constant first current I by using, for example, a silicided resistor and / or a metal resistor as combined with Figure 1 and Figure 2 . The switched capacitor 20 can generate an opposite second current I in -. The difference between the two currents I in + and I in - can be integrated by the integrator 22, and the obtained integrated 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 integrated signal 24 can correspond to an output voltage V in -, an output current I out , or an output digital signal D out . The output frequency signal 28 of the oscillator 26 can control the current I out - generated by the switched capacitor 20 in a feedback loop. In a non-limiting example, the output frequency f in can have a value of about 80 MHz or about 100 MHz, but can be different in other examples out .

[0031] Now referring to Figure 4 , the oscillator circuit 400 can include Figure 3Some or all of the features of the oscillator circuit 300. The oscillator circuit 400 can be regarded as a more detailed version of the oscillator circuit 300. The 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. The oscillator 26 of the oscillator circuit 400 can include or can correspond to a ring oscillator or a relaxation type oscillator. In the illustrated example, the oscillator 26 can be a ring oscillator including an odd number (here: three) of inverters forming an inverter chain. The oscillator circuit 400 can also include a current source 42 electrically coupled to the output of the OTA 36 and the input of the oscillator 26. The output current provided by the current source 42 can be controlled based on the integration signal of the integrator. The output current of the current source 42 can be configured to control the output frequency f out . In other examples, the oscillator circuit 400 can include a voltage source that is controlled by the integration signal and is configured to provide an output voltage for controlling the output frequency f out of the oscillator 26.

[0032] The switched capacitor 20 can be substantially unaffected by mechanical stress. In the first switch state, the switch can be in the upper position, and the capacitor 20 can be charged by the current I in + provided by the current source 100. In the second switch state, the switch can be in the lower position and can discharge the capacitor 20. In other words, during operation, the current I in + can charge the switched capacitor 20, but switching the capacitor 20 at the switching frequency f sw can also cause the switched capacitor 20 to discharge periodically. This constant charging and discharging of the switched capacitor 20 can generate an opposing current I in - provided by the switched capacitor 20. In particular, the generated opposing current I in - can be proportional to the switching frequency f sw of the switched capacitor 20. The higher the switching frequency f sw , the higher the generated current I in -. Due to the loop of the circuit, the frequency-dependent opposing current I in - can be regulated to the current I in + provided by the current source 100. Therefore, in the balanced state, the average voltage of the capacitor 20 can match a constant reference voltage V ref . The objective of the oscillator circuit 400 can thus be seen when regulating the average voltage of the capacitor 20 in the loop to match the reference voltage V ref .

[0033] If the average voltage of the capacitor 20 deviates from the reference voltage Vref , a voltage difference can be applied at the input of the OTA 36. Then, the OTA 36 can act as a voltage-current converter and can output a current signal 46 according to the applied voltage difference. The current signal 46 output by the OTA 36 can load the capacitor 38 and can be integrated by the integrator. In this case, the resistor 40 can be configured to provide dynamic compensation. The voltage established across the capacitor 38 can be proportional to the integral of the charging current 46 over time. The integrated current can be converted into a voltage signal 48 that controls the current source 42. The output signal of the current source 42 can control the oscillator 26, and in this case the oscillator 26 can be a current-controlled oscillator (ICO). Additionally, the output frequency signal 28 provided by the oscillator 26 can control the switching frequency f of the switched capacitor 20 sw . The control loop allows the oscillator 26 to stabilize in an equilibrium state, such that a constant output frequency f can be provided out .

[0034] In some examples, the frequency divider 30 can be considered optional. The frequency divider 30 can be configured to divide the frequency f of the output frequency signal 28 out by a factor div. In non-limiting examples, the factor div can have a value of 10, 16, or 32. By switching the switched capacitor 20 at a reduced switching frequency f sw , dynamic effects (such as parasitic capacitance) can be reduced or can become negligible, such that the operation accuracy of the oscillator circuit 400 can be enhanced.

[0035] Now referring to Figure 5 , the oscillator circuit 500 can include some or all of the features of the previously described oscillator circuit. The oscillator circuit 500 can include an operational amplifier integrator having an operational amplifier 50, a capacitor 38, and a resistor 40. Similar to Figure 4 the example, if the average voltage of the switched capacitor 20 deviates from the reference voltage V ref , then a voltage difference can be applied at the input 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. This voltage signal can control the oscillator 26, and in this case, the oscillator 26 can be a voltage-controlled oscillator (VCO).

[0036] Now referring to Figure 6 , the oscillator circuit 600 can include some or all of the features of the previously described oscillator circuit. The oscillator circuit 600 can include a comparator 52 and a digital integrator 54 arranged downstream. Similar to the previous example, if the average voltage of the switched capacitor 20 deviates from the reference voltage V ref, a voltage difference can be applied at the input of comparator 52. Digital integrator 54 can perform integration based on the output signal of comparator 52. Based on the performed integration, digital integrator 54 can output a signal for controlling current source 42. The output signal of current source 42 can control oscillator 26, and in this case oscillator 26 can be a current controlled oscillator (ICO).

[0037] Now referring to Figure 7 , another oscillator circuit 700 is shown in accordance with, which may include some or all of the features of the previously described oscillator circuit. Oscillator circuit 700 may include a PTAT voltage source 56 configured to provide a voltage V proportional to absolute temperature ptat . In addition, reference voltage source 58 may be configured to provide a reference voltage V ref2 . The RC element of oscillator circuit 700 may include switched capacitor 20 and silicided and / or metal resistor 4. Oscillator circuit 700 may also include an integrator, which may include OTA 36, capacitor 38, and resistor 40 in the example shown. The first input of OTA 36 may be configured to receive a first input signal based on the reference voltage V ref2 and the output voltage of the RC element. The second input of OTA 36 may be configured to receive a second input signal based on the voltage V ptat . The integrator may be configured to perform integration based on the difference or sum of the first input signal and the second input signal, and provide an integration signal based on the integration. Oscillator circuit 700 may also include an oscillator 26 configured to provide an output frequency signal 28, where 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 oscillator 26.

[0038] In the example shown, contrary to the previous example of using silicide and / or metal resistors in a current source, silicide and / or metal resistor 4 may be used in the RC element. Note that Figure 7 's integrator may be similar to the integrator described in connection with Figure 4 . Similar to the previous example, the control loop of the circuit may allow oscillator 26 to stabilize to an equilibrium state, thereby providing a constant output frequency f out .

[0039] The previously described oscillator circuit may include other components that are not shown for simplicity. For example, the oscillator circuit according to the present 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 representing the temperature of the oscillator circuit. The mechanical stress sensor may be configured to provide a second sensor signal representing the mechanical stress in the silicide resistor and / or the metal resistor 4. In addition, the oscillator circuit may include a (digital or analog) processing unit configured to adjust the reference voltage V based on at least one of the first sensor signal or the second sensor signal. ref , voltage V ptat , the division factor div of the divider 30 or the switched capacitor 20. The described regulation performed by the processing unit and based on the provided sensor signal may allow a digitally assisted compensation of residual and higher order mechanical stresses and temperature effects.

[0040] Reference now Figure 8 , a flow chart of a method for providing a periodic frequency signal according to the present disclosure is shown. The method is described in a general manner in order to qualitatively specify aspects of the present disclosure. For example, the method can be performed by one of the aforementioned oscillator circuits. It should be understood that the method can include other aspects. For example, the method can be expanded by combining any of the other discussed aspects described herein.

[0041] At 60, a first current may be provided using a temperature and mechanical stress compensation current source. At 62, a second current may be provided using a switched capacitor. At 64, an integrator may be used to perform integration based on a difference between the first current and the second current. An integrated signal may be provided based on the integration. At 66, an output frequency signal provided by an oscillator may be controlled based on the integrated signal. At 68, the second current provided by the switched capacitor may be controlled based on the output frequency signal provided by the oscillator.

[0042] Figure 8 The method may include one or more other steps that may be considered optional. For example, referring to the frequency divider 30 of the aforementioned example, the frequency divider may provide a switching frequency signal based on the output frequency signal provided by the oscillator. In another step, the second current provided by the switched capacitor may be controlled based on the switching frequency signal.

[0043] The oscillator circuit according to the present disclosure can provide the following exemplary technical effects, and based on this, is superior to conventional devices in various aspects.

[0044] As combined Figure 1 and Figure 2As described in the examples, due to the analog pre - compensation of mechanical stress and temperature effects, the current source of the oscillator circuit described herein can be temperature and mechanical stress compensated. In addition, digital - assisted compensation for the remaining and higher - order mechanical stress and temperature effects can be provided. As a result, the oscillator circuit described herein can provide a high and stable output frequency. The oscillator circuit can provide high stability against temperature, lifetime, and aging effects caused by mechanical and partial electrical stress.

[0045] Conventional oscillator circuits such as relaxation oscillators may suffer from delay effects (and accompanying aging effects) caused by the use of comparators. This delay effect, for example caused by mechanical stress, may drift during the lifetime. In oscillator circuits using comparators, the delay effect typically affects the target frequency by about 0.5 - 3%. The oscillator circuit according to the present disclosure can be immune to the above - mentioned delay effects. The delay effect can actually be reduced to 0%. Any remaining delay effect in the entire circuit is also only considered as a second - order approximation and is less than about 0.1% in any case.

[0046] The oscillator circuit described herein can provide a high output frequency at low power consumption. In addition, the concepts discussed can achieve low power consumption with additional duty - cycle operation to further reduce power consumption. In a non - limiting example, the oscillator circuit described herein can be used in high - speed interfaces for sensors, battery - powered Internet - of - Things sensor nodes with low power consumption, high - speed inductive angle sensors, etc.

[0047] Example

[0048] Hereinafter, an oscillator circuit, a current source, and a method for providing a periodic frequency signal according to the present disclosure are described by way of examples.

[0049] Example 1 is an oscillator circuit, comprising: a temperature and mechanical stress compensated current source configured to provide a first current; a switched capacitor configured to provide a second current; an integrator configured to perform integration based on the difference between the first current and the second 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, and wherein the second current provided by the switched capacitor is controlled in a feedback loop based on the output frequency signal of the oscillator.

[0050] Example 2 is the oscillator circuit according to Example 1, wherein the compensated current source includes a PTAT voltage source configured to provide a voltage proportional to the absolute temperature (VPTAT), and wherein the PTAT voltage source includes a silicided resistor and / or a metal resistor.

[0051] Example 3 is the oscillator circuit according to Example 2, wherein the compensation current source includes a PTAT current source configured to provide a current proportional to the absolute temperature (IPTAT), and the PTAT current source includes a bandgap reference circuit.

[0052] Example 4 is the oscillator circuit according to Example 3, wherein: the value of IPTAT depends on a first temperature coefficient based on VPTAT, the value of the silicided resistor and / or the metal resistor depends on a second temperature coefficient, and the first temperature coefficient substantially matches the second temperature coefficient.

[0053] Example 5 is the oscillator circuit according to any one of Examples 2 to 4, wherein the silicided resistor and / or the metal resistor form an L-shaped resistor.

[0054] Example 6 is the oscillator circuit according to any one of the foregoing examples, further comprising: a frequency divider configured to provide a switching frequency signal based on an output frequency signal provided by the oscillator, wherein the switching frequency signal is configured to control a second current provided by a switched capacitor.

[0055] Example 7 is the oscillator circuit according to any one of the foregoing 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 compensation current source and the switched capacitor, and a second input of the integrator is electrically coupled to the reference voltage source.

[0056] Example 8 is the oscillator circuit according to any one of the foregoing examples, wherein the oscillator includes a ring oscillator or a relaxation oscillator.

[0057] Example 9 is the oscillator circuit according to any one of Examples 2 to 8, wherein the compensation current source further includes a constant voltage source configured to provide a substantially constant voltage, and the constant voltage source includes a non-silicided polysilicon resistor.

[0058] Example 10 is the oscillator circuit according to Example 9, wherein: the current provided by the compensation current source is generated based on a first current and a second current, the first current depends on the values of VPTAT and the silicided resistor and / or the metal resistor, and the second current depends on the values of the constant voltage and the non-silicided polysilicon resistor.

[0059] Example 11 is the oscillator circuit according to Example 10, wherein: the current provided by the compensation current source depends on the subtraction or addition of the second current and the first current weighted by a weighting factor, and the weighting factor is adjusted to reduce the mechanical stress dependence of the current provided by the compensation current source.

[0060] Example 12 is an oscillator circuit according to any of the foregoing 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 representing the temperature of the oscillator circuit, and wherein the mechanical stress sensor is configured to provide a second sensor signal representing the mechanical stress in the silicide resistor and / or the metal resistor; and a processing unit configured to adjust at least one of the reference voltage, VPTAT, the 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.

[0061] Example 13 is an oscillator circuit according to any of the foregoing examples, further comprising: another voltage source or current source, wherein the output voltage or output current provided by the another voltage source or current source is controlled based on the integration signal of the integrator, and wherein the output voltage or output current is configured to control the output frequency of the oscillator.

[0062] Example 14 is the oscillator circuit according to Example 13, wherein the integrator includes an operational transconductance amplifier electrically coupled to another voltage source or current source.

[0063] Example 15 is the oscillator circuit according to Example 13, wherein the integrator includes a digital integrator electrically coupled to another voltage source or current source.

[0064] Example 16 is an oscillator circuit, comprising: a PTAT voltage source configured to provide a voltage (VPTAT) proportional to the absolute temperature; a reference voltage source configured to provide a reference voltage; an RC element including a switched capacitor and a silicide and / or a 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 the output voltage of the RC element, and a second input of the integrator is configured to receive a second input signal based on VPTAT, wherein the integrator is configured to perform integration based on the difference or sum of the first input signal and the second input signal, and 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, and wherein the switched capacitor is controlled in a feedback loop based on the output frequency signal of the oscillator.

[0065] Example 17 is a current source configured to provide a temperature and mechanical stress compensated current, the current source comprising: a PTAT voltage source configured to provide a voltage (VPTAT) proportional to the absolute temperature, wherein the PTAT voltage source includes a silicided polysilicon resistor and / or a metal resistor.

[0066] Example 18 is the current source according to Example 17, wherein: the value of VPTAT depends on a first temperature coefficient, the value of the polysilicon silicide resistor and / or the metal resistor depends on a second temperature coefficient, and the first temperature coefficient substantially matches the second temperature coefficient.

[0067] Example 19 is a method for providing a periodic frequency signal, the method comprising: providing a first current using a temperature and mechanical stress compensated current source; providing a second current using a switched capacitor; performing integration using an integrator based on the difference between the first current and the second current so as to provide 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 current provided by the switched capacitor based on the output frequency signal provided by the oscillator.

[0068] Example 20 is the 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 current provided by the switched capacitor based on the switching frequency signal.

[0069] Although the present disclosure has been described with reference to illustrative examples, the 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 present disclosure, will be apparent to those skilled in the art upon reference to this specification. Accordingly, the appended claims are intended to cover any such modifications or examples.

Claims

1. An oscillator circuit comprising: A temperature and mechanical stress compensation current source (100, 200) is configured to provide a first current; A switched capacitor (20) configured to provide a second current; an integrator (22) configured to perform integration based on a difference between the first current and the second current, and to provide an integrated signal (24) based on the integration; as well as an oscillator (26) configured to provide an output frequency signal (28), wherein the output frequency signal (28) is controlled based on the integrated signal (24) provided by the integrator (22), The second 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 compensation current source ( 100 , 200 ) 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 a metal resistor ( 4 ).

3. The oscillator circuit of claim 2, wherein the compensation current source (100, 200) 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.

4. The oscillator circuit according to claim 3, wherein: The value of the IPTAT depends on a first temperature coefficient based on the VPTAT, The value of the silicide resistor and / or metal resistor (4) depends on a second temperature coefficient, and The first temperature coefficient substantially matches the second temperature coefficient.

5. The oscillator circuit according to any one of claims 2 to 4, wherein the silicided resistor and / or metal resistor (4) forms an L-shaped resistor.

6. The oscillator circuit according to any 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), The switching frequency signal (32) is configured to control the second current provided by the switched capacitor (20).

7. An oscillator circuit according to any one of the preceding claims, further comprising: A reference voltage source (34) is configured to provide a reference voltage, A first input of the integrator (22) is electrically coupled to the compensation 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. An oscillator circuit according to any one of the preceding claims, wherein the oscillator (26) comprises a ring oscillator or a relaxation oscillator.

9. The oscillator circuit according to any one of claims 2 to 8, wherein the compensation current source (100, 200) further comprises a constant voltage source configured to provide a substantially constant voltage, wherein the constant voltage source comprises a non-silicided polysilicon resistor (14).

10. The oscillator circuit of claim 9, wherein: The current provided by the compensation current source (100, 200) is generated based on the first current and the second current, The first current depends on the VPTAT and the value of the silicided resistor and / or metal resistor (4), and The second current depends on the constant voltage and the value of the non-silicided polysilicon resistor (14).

11. The oscillator circuit of claim 10, wherein: The current provided by the compensation current source (100, 200) depends on the subtraction or addition of the second current and the first current weighted by a weighting factor, and The weighting factor is adjusted to reduce the mechanical stress dependency of the current provided by the compensation current source (100, 200).

12. The oscillator circuit according to any 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 the temperature of the oscillator circuit, wherein the mechanical stress sensor is configured to provide a second sensor signal representative of the mechanical stress in the silicided resistor and / or the metal resistor (4), and A processing unit is configured to adjust at least one of the switching capacitor (20) or the frequency division factor of the frequency divider (30), the VPTAT, and the reference voltage based on at least one of the first sensor signal or the second sensor signal.

13. The oscillator circuit according to any one of the preceding claims, further comprising: Another voltage source or current source (42), wherein an output voltage or output current provided by the another voltage source or current source (42) is controlled based on the integrated 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. An oscillator circuit according to claim 13, wherein the integrator (22) comprises an operational transconductance amplifier (36) electrically coupled to the further voltage or current source (42).

15. The oscillator circuit of claim 13, wherein the integrator (22) comprises a digital integrator (54) electrically coupled to the further voltage or current source (42).

16. An 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; RC element, comprising a switched capacitor (20) and a silicided and / or metal 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 the 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 integration based on a difference or a sum of the first input signal and the second input signal, and to provide an integrated signal (24) based on the integration; as well as an oscillator (26) configured to provide an output frequency signal (28), wherein the output frequency signal (28) is controlled based on the integrated signal (24) provided by the integrator (22), The switched capacitor (20) is controlled in a feedback loop based on the output frequency signal (28) of the oscillator (26).

17. A current source (100, 200) configured to provide a temperature and mechanical stress compensation current, the current source comprising: A PTAT voltage source is configured to provide a voltage proportional to absolute temperature (VPTAT), wherein the PTAT voltage source comprises a silicided polysilicon resistor and / or a metal resistor (4).

18. The current source of claim 17, wherein: The value of the VPTAT depends on the first temperature coefficient, The value of the silicided polysilicon resistor and / or the metal resistor (4) depends on a second temperature coefficient, and The first temperature coefficient substantially matches the second temperature coefficient.

19. A method for providing a periodic frequency signal, the method comprising: Using a temperature and mechanical stress compensation current source (100, 200) to provide a first current; Providing a second current using a switched capacitor (20); performing integration based on a difference between the first current and the second current using an integrator (22), thereby providing an integrated signal (24) based on the integration; controlling an output frequency signal (28) provided by an oscillator (26) based on the integrated signal (24); and The second current provided by the switched capacitor (20) is controlled based on an output frequency signal (28) provided by an oscillator (26).

20. The method according to claim 19, further comprising: using a frequency divider (30) to provide a switching frequency signal (32) based on the output frequency signal (28), and The second current provided by the switched capacitor (20) is controlled based on the switching frequency signal (32).

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