On-chip temperature sensing arrangement and method for on-chip temperature sensing

Abstract

According to the invention, an on-chip temperature sensing arrangement comprises: - a current integrating modulator (2) comprising: - an input port (21) for receiving a current signal, and - an output port (31) for generating a count value dependent on the current received at the input port (21), - a temperature sensor setup (4) for generating a current dependent on temperature and comprising: - an amplifier (41) and a resistor (42), and - another amplifier (47) and another resistor (48), - a further resistor (40), - a switch (55) for connecting the temperature sensor setup (4) with the current integrating modulator (2), and - another switch (61) for connecting the resistor (40) with the current integrating modulator (2), wherein the switch (55) and the switch (61) are connected alternately. Furthermore, a corresponding method for on-chip temperature sensing is disclosed.

Description

[0001] 2023PF01108

[0002] 1

[0003] ON-CHIP TEMPERATURE SENSING ARRANGEMENT AND METHOD FOR ON-CHIP TEMPERATURE SENSING

[0004] DESCRIPTION

[0005] TECHNICAL FIELD

[0006] The present invention relates to an on-chip temperature sensing arrangement and a method for on-chip temperature sensing .

[0007] BACKGROUND

[0008] The continuous advancement in semiconductor technology has resulted in a miniaturization of integrated circuits ( ICs) . This miniaturization, while advantageous in terms of space efficiency and processing speed, has led to an escalation in power densities .

[0009] As a direct consequence, there is a substantial increase in the operating temperatures of these ICs . These heightened temperatures can have adverse effects on the device, impacting its reliability due to increased risk of thermal runaway, degrading its performance due to increased leakage currents, and reducing its lifespan due to accelerated aging processes .

[0010] Therefore, thermal management is needed for maintaining the device' s operational efficiency and ensuring its longevity. Effective thermal management strategies can include heat sinks, on-chip temperature sensors, and dynamic thermal management techniques .

[0011] On-chip temperature sensors can be built into a microchip and are a part of the integrated circuit or be separate . They are designed to gauge the temperature of the chip' s surroundings .2023PF01108

[0012] A particular application of an on-chip temperature sensor is to measure the junction temperature .

[0013] Usually, on-chip temperature sensors function by gauging a voltage that varies with temperature . This is typically accomplished using the base-emitter voltage (VBE) of a bipolar junction transistor, which exhibits a negative temperature coefficient, and a variation in base-emitter voltage (AVBE) , which displays a positive temperature coefficient . By measuring these voltages, the sensor can ascertain the junction temperature .

[0014] However, these voltage measurements are in the form of analog signals . In a multitude of applications, it becomes a necessity to transform these analog signals into a digital format . This conversion from analog to digital is generally executed using an analog-to-digital converter (ADC) .

[0015] In this context, two types of ADCs are commonly employed -Delta-Sigma ADCs and Successive Approximation Register (SAR) ADCs . These ADCs transfigure the measured voltages (VBE and AVBE) into a digital format . The conversion process often involves the computation of certain ratios such as VBE / AVBE or AVBE / VREF, where VREF is a reference voltage .

[0016] To utilize the temperature sensor, it needs to be activated along with the ADC and its related bias circuitry. The temperature sensor might be chosen as the input to the ADC .

[0017] However, the sensor gauges the die temperature of the device, so if an ambient temperature measurement is needed, the impact of device self-heating must be considered.

[0018] While on-chip temperature sensors offer numerous advantages, they also come with certain disadvantages . One of the primary issues is the mismatch in Bipolar Junction Transistor (BJT) and curvature . This mismatch can lead to inaccuracies in temperature measurement, which can affect the overall performance of the system.2023PF01108

[0019] 3

[0020] Another disadvantage is the larger area consumption on the chip . On-chip temperature sensors, especially those with high precision, can occupy a significant amount of silicon area . This can be a limiting factor in highly integrated systems where space is at a premium.

[0021] In addition, these sensors can consume more power compared to other components . This increased power consumption can contribute to the overall heat generation of the system, potentially exacerbating the very problem the sensor is designed to monitor .

[0022] Furthermore, the need for AVBE slope correction can add complexity to the system. The slope of the base-emitter voltage (VBE) versus temperature is not constant and can vary with temperature . This requires a correction mechanism, which can add to the design complexity and power consumption.

[0023] Finally, curvature correction is another challenge . The relationship between the base-emitter voltage and temperature is not perfectly linear but has a slight curvature . This curvature needs to be corrected for accurate temperature measurement, which can add to the complexity and power consumption of the system.

[0024] SUMMARY

[0025] The obj ect of the present invention is therefore to provide on-chip temperature sensing arrangement and a method for on-chip temperature sensing, which solve the above addressed problems and present a solution with high accuracy yet having a lower area and power consumption.

[0026] According to the invention, the obj ect is met by a device specified in claim 1 and by a method with the steps specified in claim 11 .2023PF01108

[0027] 4

[0028] Therefore, an on-chip temperature sensing arrangement is proposed by the invention, comprising:

[0029] - a current integrating modulator comprising:

[0030] - an input port for receiving a current signal, and - an output port for generating a count value dependent on the current received at the input port,

[0031] - a temperature sensor setup for generating a current dependent on temperature and comprising:

[0032] - an amplifier and a resistor, and

[0033] - another amplifier and another resistor,

[0034] - a further resistor,

[0035] - a switch for connecting the temperature sensor setup with the current integrating modulator, and

[0036] - another switch for connecting the resistor with the current integrating modulator,

[0037] wherein the switch and the switch are connected alternately .

[0038] The architecture under discussion offers a novel approach to temperature measurement, effectively eliminating common errors found in previous methods . These errors include the need for AVBE slope correction, the mismatch in Bipolar Junction Transistors (BJTs) , and the requirement for curvature correction .

[0039] This architecture is designed to perform the measurements of a current ICTAT1 and another current, ICTAT2 . These currents are time-interleaved, a technique that allows for the simultaneous measurement of two different parameters .2023PF01108

[0040] 5

[0041] Another feature of this architecture is the implementation of a one-point trimming process at 35°C . This is achieved by applying reference voltages VREF1 and VREF2 through a resistor connected to a trans-impedance amplifier . This process ensures the accuracy of the measurements and reduces the need for frequent calibration.

[0042] The architecture multiplexes the output of the temperature sensor to a ambient light sensor (ALS ) / proximity architecture . This approach allows for high-accuracy temperature measurements .

[0043] This architecture is efficient, as it reduces the chip area required in all optical sensor devices . Additionally, it offers rapid temperature conversion, which significantly conserves power .

[0044] This architecture furthermore enables the accurate measurement of on-die junction temperature . It does so with a low area and low power consumption. Furthermore, it includes a one-point trimming process at 35°C, making it suitable for all optical sensors .

[0045] In a preferred embodiment of the invention, the current integrating modulator further comprises an integration

[0046] amp 1 i f i e r .

[0047] An integration amplifier uses an operational amplifier, which incorporates a capacitive component within its feedback loop . Usually, an analog integrator is characterized by the use of an operational amplifier, with a capacitor serving as a feedback component . The integrator' s output voltage is a function of the input voltage, and its value can be determined through a specific mathematical formula .

[0048] With this, the precision of the system is enhanced by minimizing discrepancies that arise from fluctuations in the signal . Furthermore, the signal-to-noise ratio is improved, thus enabling a clearer and more dependable signal2023PF01108

[0049] 6

[0050] transmission. Additionally, the integration amplifier has the ability to amplify signals of low amplitude to a level that can be quantified, thereby streamlining the process of data analysis and interpretation.

[0051] In a further preferred embodiment of the invention, the current integrating modulator further comprises an integration capacitor, which is connected to the integration amplifier .

[0052] An integration capacitor can store and accumulate the incoming current over time, effectively integrating the signal . This is particularly beneficial, when the signal varies over time or when the signal has a complex waveform.

[0053] With this, fluctuations in the input signal can be smoothed out, thereby enhancing the stability and reliability of the system.

[0054] Furthermore, it can, in conjunction with the integration amplifier, amplify weak signals to a level that can be easily processed and interpreted, and it provides better control over the output, allowing for more precise adjustments and fine-tuning of the system.

[0055] According to another embodiment of the invention, the current integrating modulator further comprises a comparator, which is connected downstream the integration amplifier .

[0056] A comparator has the ability to differentiate between varying signal intensities . It performs a comparison between the signal that has been amplified by the integration amplifier and a reference signal, and then produces an output signal based on this comparison.

[0057] The comparator is also capable of transforming analog signals into digital ones .

[0058] In another preferred embodiment of the invention, the current integrating modulator further comprises a latch, which is connected downstream the comparator .2023PF01108

[0059] 7

[0060] A latch retains and preserves the output from the comparator . In addition, the latch contributes to the stabilization of the comparator' s output . By maintaining the output, it can inhibit abrupt alterations or oscillations in the output signal, thereby boosting the system' s stability and dependability.

[0061] Furthermore, the latch aligns the output with other components of the system. It can preserve the output until a distinct clock signal or trigger is detected, guaranteeing that the output is in sync with the entire system.

[0062] According to another preferred embodiment of the invention, the current integrating modulator further comprises a counter, which is connected downstream the latch.

[0063] A counter can enumerate the quantity of input pulses . With this, the frequency or rate of the input signal is measured. Additionally, the counter can transform time-domain signals into count values, with this, input signals, which are based on time, can be converted into a format suitable for digital processing .

[0064] In a further preferred embodiment, the current integrating modulator further comprises a control device for generating control signals .

[0065] With a control device exact control signals are produced.

[0066] These signals have the potential to manage diverse facets of the system, including the scheduling of operations, the magnitude of signals, and the transition of components .

[0067] In addition, the control device can adjust to modifications in the system or its surroundings . By formulating control signals that reflect the current condition of the system or environment, the control device aids the system in adapting to changes and sustaining peak performance .

[0068] Lastly, the control device can coordinate operations within the system. Through the generation of control signals at2023PF01108

[0069] 8

[0070] specific intervals, the control device ensures the harmonious operation of different components within the system.

[0071] According to another embodiment of the invention, the resistor, the another resistor and the further resistor have the same resistance .

[0072] Using resistors with the same resistance has the advantage, if these resistors are connected in parallel, they will each carry the same amount of current . Then equal power is delivered to different parts of a circuit .

[0073] In a further preferred embodiment of the invention, the current integrating modulator, the temperature sensor setup and the further resistor are disposed on the same integrated circuit .

[0074] The integration of these components onto a single chip results in compactness, significantly diminishing the overall system size . The system efficiency is also enhanced due to the close proximity of the components, which reduces signal transmission times and thereby accelerates response times and boosts operating speeds . Furthermore, the presence of the temperature sensor setup on the same integrated circuit facilitates improved thermal regulation, allowing for more precise monitoring and control of the system' s temperature, thereby preventing overheating and improving system longevity.

[0075] Furthermore, the invention proposes a light sensor setup,

[0076] comprising :

[0077] the on-chip temperature sensing arrangement, and

[0078] - a photodiode coupled to current integrating modulator through a switch, the current integrating modulator configured to perform an offset compensation of the integration amplifier in response to the count values generated for the temperature sensor setup and for the further resistor .2023PF01108

[0079] 9

[0080] o ■©

[0081] With this arrangement, an ambient light sensor or a proximity sensor can be compiled. This is a type of semiconductor device that is capable of converting light into an electrical current . The current produced by the photodiode is contingent on the intensity of the ambient light to which it is exposed.

[0082] The photodiode might use the same current integrating modulator as the temperature sensor setup does and with this, the resource utilization is optimized with only a minimal increment in the space requirements on the integrated circuit and a very moderate increase in power consumption. This renders it a highly efficient and effective solution for a variety of applications .

[0083] In ALS / Proximity / Color / f licker sensors, photodiode currents are detected using a trans-impedance amplifier with a first-order modulator . The same circuitry is reused when measuring the temperature, with time interleaving between photocurrent and the temperature-dependent current .

[0084] Furthermore, the invention proposes a method for on-chip temperature sensing, the method comprising the following steps :

[0085] - providing an on-chip temperature sensing arrangement, comprising :

[0086] - a current integrating modulator comprising:

[0087] o an input port for receiving a current signal, and

[0088] o an output port for generating a count value dependent on the current received at the input port,

[0089] - a temperature sensor setup for generating a current dependent on temperature and comprising:

[0090] o an amplifier and a resistor, and

[0091] o another amplifier and another resistor,

[0092] a further resistor,2023PF01108

[0093] - 10 -

[0094] - a switch for connecting the temperature sensor setup with the current integrating modulator, and

[0095] - another switch for connecting the resistor with the current integrating modulator,

[0096] wherein the switch and the switch are connected alternately,

[0097] - sensing currents and respective count values :

[0098] ■ a positive temperature coefficient current IPTAT and a respective count value,

[0099] ■ a first negative temperature coefficient current ICTAT1 and a respective count value, ■ a second negative temperature coefficient current ICTAT2 and a respective count value, ■ a current of the resistor and a respective count value,

[0100] - determining a current that is proportional to the absolute temperature current IPTAT by taking the difference between ICTAT1 and ICTAT2,

[0101] - taking the ratio between ICTAT and IPTAT,

[0102] - defining a variable for creating a linear code with respect to temperature,

[0103] - calculating a temperature, and

[0104] - performing a trimming at 35°C for correcting the slope of temperature readings across process corners .

[0105] Most temperature sensors traditionally employ a voltage that is dependent on negative temperature (VBE) and positive temperature (AVBE) to measure junction temperature . This is because the base-emitter voltage (VBE) of a bipolar junction transistor (BJT) has a temperature-dependent characteristic, which can be exploited for temperature sensing.2023PF01108

[0106] To convert this analog temperature information into a digital format, in this embodiment of the invention, an analog-to-digital converter (ADC) is used, e . g. delta sigma ADC or successive approximation register (SAR) ADC converter can be used. These converters transform the VBE / AVBE or AVBE / VREF into a digital signal that can be processed by digital systems .

[0107] However, the proposed temperature sensor takes a different approach. Instead of using temperature-dependent voltages, negative temperature-dependent currents ( ICTAT1, ICTAT2 ) are used to measure a junction temperature . These currents are generated by a circuit, which provides a current output that is inversely proportional to an absolute temperature .

[0108] IPTAT, or Positive Temperature Coefficient Current, is a current that exhibits an increase with rising temperature . On the other hand, ICTAT, or Negative Temperature Coefficient Current, is a current that decreases as temperature increases .

[0109] Generally, when designing a temperature sensor, both IPTAT and ICTAT are incorporated into the output resistance to achieve first-order compensation bandgap voltages . This method aids in counteracting the non-linear term of VBE, which stands for Voltage Base-Emitter of a Bipolar Junction Transistor (BJT) .

[0110] In addition to said circuit, also a light to digital converter (LDC) can be incorporated. The LDC converts light intensity into a digital signal, providing another dimension of environmental sensing.

[0111] To optimize the measurement process a time-interleaved method between photocurrent and ICTAT currents is employed. This technique allows to alternate between light and temperature measurements, enhancing the overall sensing capabilities of the system.2023PF01108

[0112] 12

[0113] The ICTAT-based temperature measurements address the inherent problem of mismatch in BJTs . Furthermore, the curvature issue, a common challenge in temperature sensing due to the nonlinear characteristics of semiconductors, is resolved by this method .

[0114] To further enhance the accuracy of this temperature measurements, a slope correction technique across process corners is implemented. This technique adjusts the slope of temperature readings, correcting measurement inaccuracies up to 0.5C . As a result, these combined techniques contribute to achieving a temperature error of up to 0.5C, significantly improving the precision of our temperature sensor .

[0115] Furthermore, what has been said with respect to the device may analogously be applied to the method and therefore need not be repeated there . Device embodiments and details have a counterpart in the method and vice versa .

[0116] BRIEF DESCRIPTION OF THE DRAWINGS

[0117] In the following, the invention will be described in further detail with reference to the accompanying drawing, wherein:

[0118] FIG. 1 depicts a circuit diagram of an embodiment of the invention .

[0119] Identical parts are labelled with the same reference signs .

[0120] DETAILED DESCRIPTION

[0121] In FIG. 1 an embodiment of the present invention is shown.

[0122] An on-chip temperature sensing arrangement 1 includes a current integrating modulator 2, a temperature sensor setup 4, a photodiode 50 and a resistor 40.2023PF01108

[0123] 13

[0124] The current integrating modulator 2 functions to transform an analog input signal, which could be a current indicative of a specific parameter, e . g. the temperature on a die junction or the luminosity level in an Ambient Light Sensor (ALS) , into a high-speed, single-bit, modulated pulse wave .

[0125] The current to be integrated is fed into the current integrating modulator 2 at an input port 21. An operational amplifier (op-amp) 22, which is a DC-coupled high-gain electronic voltage amplifier characterized by a differential input and typically a single-ended output, is connected to said input port 21. Its high gain attribute allows it to substantially amplify the magnitude of the input signal .

[0126] The op-amp 22 is configured as an integrator . Usually, the opamp is arranged with a resistor at its input and a capacitor in its feedback loop . The input signal is directed across the resistor, while the output signal is derived across the capacitor . The integrator op-amp generates an output voltage that corresponds proportionally to both the magnitude and the duration of the input signal .

[0127] In this embodiment, the op-amp 22 features an integration capacitor 23 that connects its negative input to its output terminal 24. Its positive input is supplied with a reference voltage, VREF. The integration voltage VFORCE is held at the negative input terminal of the op-amp 22.

[0128] The output terminal 24 of the op-amp drives the integration capacitor 23 to ensure that VFORCE equals VREF plus or minus Voffset, where Voffset represents the offset voltage of the operational amplifier op-amp 22.

[0129] A comparator, which is an electronic component that evaluates two input voltages or currents and produces a digital signal to indicate the larger of the two, is denoted with a reference sign 25.2023PF01108

[0130] 14

[0131] The comparator 25 is equipped with two analog input terminals and a single binary digital output . Ideally, the output is a digital reflection of the larger of the two input voltages or currents .

[0132] The positive input of a comparator 25 is linked to the output terminal 24 of the op-amp 22. The comparator 25' s reference input, or its negative input, is provided with a reference voltage VCOM_REF.

[0133] The comparator 25' s output 26 serves as the data input for a latch 27, which is an electronic circuit that can exist in one of two stable states, thereby having the ability to store a single bit of data . This characteristic makes it a bistable multivibrator .

[0134] Even when the input signal is no longer present, the latch 27 is able to maintain its state . This property qualifies it as a memory device, capable of holding a binary value ( 0 or 1 ) for as long as the device remains powered. The latch 27 employs a feedback path to preserve the information.

[0135] Latches come in two varieties : S-R (Set-Reset) Latches and D (Data) Latches . The simplest form of latches, S-R latches, are constructed using two inputs : S (Set) and R (Reset) . The S input sets the output to 1, while the R input resets the output to 0 . D latches, also referred to as transparent latches, are built using two inputs : D (Data) and a clock signal .

[0136] In this embodiment the latter is used and is therefore governed by a clock signal CLK1 . This clock signal could be produced on the chip by an RC oscillator with an approximate oscillation frequency of 2 MHz . The output Q of the latch 27, which carries the signal LOUT, regulates the clock input Clk of a counter 28 .

[0137] The latch output signal, denoted as LOUT, is also directed to a control device depicted as 29. This control device 29 is2023PF01108

[0138] 15

[0139] responsible for producing the control signals that govern the operation of the current integrating modulator 2. This modulator encompasses the requisite control logic and circuits to generate multiple clock signals, specifically 01, 02, and 03, which are utilized within the circuit .

[0140] The input port 21 is additionally linked to a reference capacitor 30, which is charged with the reference voltage VREF. As the device operates, the switches connected to the reference capacitor CREF are manipulated in such a way that the reference charge is deducted from the integration capacitor 23 whenever the output signal OPOUT of the op-amp 22 surpasses the threshold VCOM_REF at comparator 25. The quantity of reference charge packages subtracted from the integration capacitor 23, originating from reference capacitor 30, is tallied in counter 28 during a set integration time window and is presented as count value ADC_COUNT at the output port 31 of counter 28. This count value ADC_COUNT is indicative of the volume of current supplied to input port 21. o ■©

[0141] The temperature sensor setup 4 includes an amplifier 41, the inputs of which are connected to resistor 42. Amplifier 41 controls PMOS transistors 43, 44 that are connected to the circuit paths of the bipolar junction transistors 45, 46.

[0142] Furthermore, the temperature sensor setup 4 includes another amplifier 47, the inputs of which are connected to another resistor 48. Amplifier 48 controls PMOS transistors 49, 51 that are connected to the circuit path of the bipolar junction transistor 51 .

[0143] Furthermore, the output of amplifier 41 controls a transistor 52 which supplies a current that is mirrored through current mirror 53, 54 to the switch 55 of the temperature sensor circuit 4 and the output of amplifier 47 controls a transistor 56 which supplies a current that is also mirrored through current mirror 53, 54 to the switch 55 of the temperature sensor circuit 4 .2023PF01108

[0144] 16

[0145] The drain-source path of current mirror 54 delivers a current, denoted as ICTAT1 / ICTAT2 , that is proportional to the ambient temperature, to terminal 55. When the device is in operation and a control signal is activated, this current ICTAT1 / ICTAT2 is directed to the input port 21 of the current integrating modulator 2 . Consequently, the current integrating modulator 2 produces a count value, referred to as ADC_COUNT, which represents the volume of current supplied to input port 21.

[0146] Furthermore, the on-chip temperature sensing arrangement 1 comprises a photodiode 6. When a control signal is activated and the corresponding switch 62 is closed, photodiode 6 produces a photocurrent that is directed to the input port 21 of the current integrating modulator 2. This photocurrent is then integrated by the current integrating modulator 2 .

[0147] A compensation is needed for the dark current at the op-amp 22 when no light falls on photodiode 6. This compensation is achieved through an offset compensation process that produces an offset trim value OSTRIM [ 8 : 0] . This is then sent as a correction value to the op-amp 22.

[0148] The offset trim value is temperature-dependent, thus the precise ratio metric temperature measurement provided by the temperature sensor arrangement 4 and the resistor 40 is incorporated into the offset compensation process .

[0149] The on-chip temperature sensing arrangement 1 performs four measurements :

[0150] A first measurement is based on the current IPTAT and the corresponding count value ADC_COUNT is CIPTAT .

[0151] Another, second measurement is based on the current ICTAT1 and the corresponding count value ADC_COUNT is CICTAT1.

[0152] Another, third measurement is based on the current ICTAT2 and the corresponding count value ADC_COUNT is CICTAT2 .2023PF01108

[0153] 17

[0154] Another, fourth measurement is based on the resistor 40 using the same current integrating modulator 2 generating a corresponding count value CIR.

[0155] The count value for CIPTAT may be represented with the following calculations, wherein

[0156] AV BE = VBE2 - VBE1

[0157] with VBE1 being the base-emitter voltage of transistor 46 and VBE2 being the base-emitter voltage of transitor 45 and wherein R is the resistance value of resistor 42 and wherein

[0158] AVBE IPTAT =

[0159] R

[0160] The modulator count CIPTAT when the input current is IPTAT is given by

[0161]

[0162] wherein CF is the capacitance value of capacitor 23 and Atime represents the integration time window and is related to the clock signal of, e . g. , 2 MHz .

[0163] The modulator count CICTAT1 when the input current is resistor current ICTAT1 is given by

[0164] ICTATl*Atime VBEl*Atime CICTAT1(ADC_ COUNT)

[0165] CF*(VREF- VFORCE) R*CF*(V REF -VFORCE)2023PF01108

[0166] And the modulator count CICTAT2 when the input current is resistor current ICTAT2 is given by

[0167] ICTAT2*Atime VBE2*Atime CICTAT2(ADC_ COUNT)

[0168] CF*(VREF-VFORCE) R*CF*(V REF -V FORCE)

[0169] A Bipolar Junction Transistor (BJT) , such as the BJT 51, is a type of transistor that uses both electrons and holes as charge carriers . It has three terminals : the base, collector, and emitter . The voltage between the base and the emitter (VBE) controls the current flowing from the collector to the emitter .

[0170] The BJT has a characteristic known as reverse saturation current, which is the current that flows from the collector to the emitter when the base-emitter junction is reverse-biased (i . e . , the base voltage is lower than the emitter voltage) . This current is temperature-dependent, meaning it changes with the temperature .

[0171] The voltage VBE also changes with temperature, but in a nonlinear way. This means that a small change in temperature could cause a large change in VBE, or vice versa .

[0172] However, this nonlinearity can be reduced by biasing the bipolar junction transistor 51 with a current that is Proportional To Absolute Temperature (PTAT) . Biasing is the process of setting a predetermined voltage or current to an active device (like a BJT) to set its operating point . A PTAT current is a current that changes linearly with the absolute temperature . By using a PTAT current to bias the BJT, the changes in VBE due to temperature can be made more linear, which can improve the performance of the circuit .2023PF01108

[0173] - 19 -

[0174] Therefore, the difference between CICTAT2 and CICTAT1 is taken, which generates a process independent linearly dependent temperature code :

[0175] wherein

[0176]

[0177] and

[0178] &

[0179]

[0180] and thus

[0181]

[0182] After that, the ratio between CICTAT2 Und CIPTAT is taken:

[0183] > >

[0184]

[0185] The ratio being discussed here is independent of the resistor process, but it is nonlinear . In order to create a linear code with respect to temperature and to correct for curvature, a parameter is selected, denoted as a.2023PF01108

[0186] - 20 -

[0187] A variable p is defined as :

[0188]

[0189] This equation shows that p is linearly dependent on temperature .

[0190] The temperature T is measured such that

[0191] T = A * / J. — B

[0192] Here, A and B are constants , a is chosen in such a way that the minimum temperature error at a typical device is met . This means that a is adjusted to optimize the accuracy of this temperature measurement .

[0193] To achieve improved accuracy, the slope and offset of CIPTAT across different corners must be corrected, primarily focusing on AVBE . To achieve this, a trimming procedure by connecting a resistor R to the modulator is employed. Then constant voltages VREF1 and VREF2 for all process corners are enforced and the corresponding codes are taken.

[0194] The equations for CVREF1 and CVREF2 are given by:

[0195]

[0196] 2023PF01108

[0197] - 21 -

[0198] A typical corner as the reference corner is then choosen, which has defined values for A, a, and B . The ratio between CVREF1 and CIPTAT and between CVREF2 and CIPTAT is taken, giving us Xrefl and Xref2 respectively:

[0199] CVREF1

[0200] = XREF1

[0201] CIPTAT

[0202] CVREF2

[0203] = XREF2

[0204] CIPTAT

[0205] For example, if another process corner (other than the typical one) is taken, Xdutl and Xdut2 is received:

[0206] CVREF1

[0207] = XDUT1

[0208] CIPTAT

[0209] CVREF2

[0210] = XDUT2

[0211] CIPTAT

[0212] Those ratios do not have a resistor variation.

[0213] Furthermore, a trimming at 35°C is conducted. "Trimming" in the context of sensors refers to the process of fine-tuning or calibrating the sensor' s output to ensure its accuracy. This is typically done during the manufacturing process . Due to factors like manufacturing variations, environmental conditions, and aging, the actual output of a sensor can deviate from its expected output . This deviation is often nonlinear and can change over time, as described before .

[0214] To correct for these deviations, the sensor' s output is "trimmed" or adjusted. This is usually done by comparing the sensor' s output to a known reference under controlled conditions, and then adjusting the sensor' s output to match the reference . The adjustments can be made in hardware ( for2023PF01108

[0215] 22

[0216] example, by changing resistor values) or in software (by applying correction factors) .

[0217] Here, a one-point trimming at 35°C is performed. This means the sensor is calibrated at a single temperature point (35°C) , and this calibration is assumed to be suitable for all optical sensors . This helps to ensure that the sensor provides accurate readings across its entire operating temperature range .

[0218] In sensor calibration, the "slope" (denoted as 'K' ) is the rate at which the sensor' s output changes per unit change in the measured quantity.

[0219] During calibration, the slope is adjusted to ensure the sensor' s output accurately corresponds to the measured quantity across the entire operational range .

[0220] In a two-point calibration process, measurements are taken at two endpoints . The sensor' s output is then linearized between these points . The slope is adjusted based on these measurements to ensure accurate representation of the measured quantity across the entire range .

[0221] In temperature measurement, the slope 'K' can represent the rate at which the sensor' s output voltage or current changes per degree change in temperature . By adjusting this slope through calibration at 35°C, the sensor' s output can be made to accurately represent the temperature across the entire operational range .

[0222] The slope K at 35°C is defined as :

[0223]

[0224] 2023PF01108

[0225] - 23 -

[0226] The offset between the two corners at 35°C is defined as :

[0227] A = K * XDUT - XREF

[0228] wherein XDUT or XREF is the ratio of CICTAT2 to CIPTAT at 35°C :

[0229]

[0230] New process corner values A' and a' are received through this :

[0231]

[0232]

[0233] The temperature reading for process corners is then given by:

[0234]

[0235] Wherein X is the respective corner CICTAT2 / CIPTAT . This process helps to ensure that the ratio does not have resistor variation, leading to more accurate temperature readings .

[0236] The slopes and offsets are calibrated according to the description provided, ensuring that the measurements are accurate and reliable across different temperature points .2023PF01108

[0237] Finally, the measured temperature is calculated using specific equations, providing the final output of the temperature measurement process . This strategy allows for precise temperature measurements even when direct measurement is not possible .

[0238] It is to be noted that resistors 42, 48 and 40 can be manufactured such that they have matching resistance values . For example, resistors 42, 48 and 40 may have the same resistance value R. It may also be useful to manufacture resistors 42, 48 and 40 such that they have a known ratio of resistance values . The ratio of resistance values of resistors 42, 48 and 40 may be N: l, . . . , 1 : 1, 1 : 2, . . . 1 :N (N being integer or real) .

[0239] The sensing arrangement may be further used to measure ambient light impinging on photodiode 6 :

[0240] This integration allows the temperature sensor setup 4 to be incorporated into Ambient Light Sensing devices / proximity sensing devices without the need for additional area or power .

[0241] With this approach, the modulator 2 used for the ALS / proximity device is repurposed to measure temperature . By multiplexing the modulator 2 for the temperature sensor setup 4, it is possible to obtain temperature measurements without the need for additional power or space .

[0242] Moreover, the proposed circuit design effectively mitigates variations in each measurement . This includes process variations in resistors, capacitors, and oscillators, temperature drifts of these parameters, and the need for curvature correction and slope trimming of temperature curves across the process . This technique also reduces the mismatch in Bipolar Junction Transistors (BJTs) .

[0243] It shall be noted that the steps given above do not necessarily have to be carried out in the given order . The2023PF01108

[0244] - 25 -

[0245] provided steps may be carried out in any other suitable order or even some or all of them at the same time .

[0246] List of abbreviations :

[0247]

[0248] 2023PF01108

[0249] LIST OF REFERENCE SIGNS

[0250] On-chip temperature sensing arrangement 1 Current integrating modulator 2 Temperature sensor setup 4 Input port 21 Operational amplifier (op-amp) / integration amplifier 22 Integration capacitor 23 Output terminal 24 Comparator 25 Comparator output / data input for latch 26 Latch 27 Counter 28 Control device 29 Reference capacitor 30 Output port 31 Photodiode 50 Resistor 40 Amp lifier 41 Resistor 42 PMOS transistor 43 PMOS transistor 44 Bipolar junction transistor 45 Bipolar junction transistor 46 Amp lifier 47 Resistor 48 PMOS transistor 49 Photodiode 50 PMOS transistor 51 Bipolar junction transistor 51 Transistor 52 Current mirror 53 Current mirror 54 Switch 55 Transistor 56 Switch 62 Clock signal 01 Clock signal 02 Clock signal 03

Claims

2023PF01108CLAIMS1 . An on-chip temperature sensing arrangement ( 1 ) , comprising :- a current integrating modulator ( 2 ) comprising :- an input port ( 21 ) for receiving a current signal , and- an output port ( 31 ) for generating a count value dependent on the current received at the input port ( 21 ) ,- a temperature sensor setup ( 4 ) for generating a current dependent on temperature and comprising :- an ampli fier ( 41 ) and a resistor ( 42 ) , and - another ampli fier ( 47 ) and another resistor ( 48 ) ,- a further resistor ( 40 ) ,- a switch ( 55 ) for connecting the temperature sensor setup ( 4 ) with the current integrating modulator ( 2 ) , and- another switch ( 61 ) for connecting the resistor ( 40 ) with the current integrating modulator ( 2 ) ,wherein the switch ( 55 ) and the switch ( 61 ) are connected alternately .2 . The on-chip temperature sensing arrangement ( 1 ) according to claim 1 ,wherein the current integrating modulator ( 2 ) further comprises an integration ampli fier ( 22 ) .3 . The on-chip temperature sensing arrangement ( 1 ) according to any one of the preceding claims ,2023PF01108wherein the current integrating modulator ( 2 ) further comprises an integration capacitor ( 23 ) , which is connected to the integration ampli fier ( 22 ) .4 . The on-chip temperature sensing arrangement ( 1 ) according to any one of the preceding claims ,wherein the current integrating modulator ( 2 ) further comprises a comparator ( 25 ) , which is connected downstream the integration ampli fier ( 22 ) .5 . The on-chip temperature sensing arrangement ( 1 ) according to any one of the preceding claims ,wherein the current integrating modulator ( 2 ) further comprises a latch ( 27 ) , which is connected downstream the comparator ( 25 ) .6 . The on-chip temperature sensing arrangement ( 1 ) according to any one of the preceding claims ,wherein the current integrating modulator ( 2 ) further comprises a counter ( 28 ) , which is connected downstream the latch ( 27 ) .7 . The on-chip temperature sensing arrangement ( 1 ) according to any one of the preceding claims ,wherein the current integrating modulator ( 2 ) further comprises a control device ( 29 ) for generating control signals .8 . The on-chip temperature sensing arrangement ( 1 ) according to any one of the preceding claims , wherein the resistor ( 42 ) , the another resistor ( 48 ) and the further resistor ( 40 ) have the same resistance .9 . The on-chip temperature sensing arrangement ( 1 ) according to any one of the preceding claims , wherein the current integrating modulator ( 2 ) , the temperature sensor setup ( 4 ) and the further resistor ( 40 ) are disposed on the same integrated circuit .2023PF01108- 29 -10 . A light sensor setup, comprising :- the on-chip temperature sensing arrangement ( 1 ) according to any one of the preceding claims , and- a photodiode ( 50 ) coupled to the current integrating modulator ( 2 ) through a switch ( 62 ) , the current integrating modulator ( 2 ) configured to perform an of fset compensation of the integration ampli fier ( 22 ) in response to the count values generated for the temperature sensor setup ( 4 ) and for the further resistor ( 40 ) .11 . A method for on-chip temperature sensing, the method comprising the following steps :- providing an on-chip temperature sensing arrangement ( 1 ) , comprising :- a current integrating modulator ( 2 ) comprising :o an input port ( 21 ) for receiving a current signal , ando an output port ( 31 ) for generating a count value dependent on the current received at the input port ( 21 ) ,- a temperature sensor setup ( 4 ) for generating a current dependent on temperature and comprising :o an ampli fier ( 41 ) and a resistor ( 42 ) , and o another ampli fier ( 47 ) and another resistor ( 48 ) ,- a further resistor ( 40 ) ,- a switch ( 55 ) for connecting the temperature sensor setup ( 4 ) with the current integrating modulator ( 2 ) , and2023PF01108- another switch ( 61 ) for connecting the resistor (40) with the current integrating modulator (2 ) ,wherein the switch (55) and the switch ( 61 ) are connected alternately,- sensing currents and respective count values :■ a positive temperature coefficient current IPTAT and a respective count value,■ a first negative temperature coefficient current ICTAT1 and a respective count value, ■ a second negative temperature coefficient current ICTAT2 and a respective count value, ■ a current of the resistor 40 and a respective count value,- determining a current that is proportional to the absolute temperature current IPTAT by taking the difference between ICTAT1 and ICTAT2,- taking the ratio between ICTAT and IPTAT,- defining a variable for creating a linear code with respect to temperature,- calculating a temperature, and- performing a trimming at 35°C for correcting the slope of temperature readings across process corners .

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