CN109724711B - Temperature sensor and temperature sensing method - Google Patents
Temperature sensor and temperature sensing method Download PDFInfo
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- CN109724711B CN109724711B CN201910047703.2A CN201910047703A CN109724711B CN 109724711 B CN109724711 B CN 109724711B CN 201910047703 A CN201910047703 A CN 201910047703A CN 109724711 B CN109724711 B CN 109724711B
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Abstract
The invention discloses a temperature sensor and a temperature sensing method, wherein the temperature sensor is provided with an enable end EN, a START end START and an output end Dout; (1) the first output end (Ipt 1) of the current source is connected with the e pole of the triode, (2) the second output end (Ipt 2) of the current source is connected with the D pole of the MOS tube; the S pole of the MOS tube is grounded, and the START end START is connected with the G pole of the MOS tube through the NOT gate; (3) the e pole of the triode is connected with the non-inverting input end of the comparator; the D pole of the MOS tube is connected with the inverting input end of the comparator; (4) the enable end EN and the input End (EN) of the current source are both connected with the first input end of the NAND gate, and the output end of the comparator is connected with the second input end of the NAND gate; the output end of the NAND gate is connected with the R end of the RS trigger. The temperature sensor and the temperature sensing method are easy to implement and convenient to use.
Description
Technical Field
The invention relates to a temperature sensor and a temperature sensing method.
Background
The conventional temperature sensor is realized by using an off-chip discrete element, and a temperature sensor chip has the advantages of low manufacturing cost and simple interface with other electronic circuits, can be integrated into an SOC (system on chip) and has wide market demand.
Although the double-point calibration is a common method adopted by a common ADC at present, the temperature sensor is different from the common ADC, when the double-point calibration is carried out, VREF _ L OW is input firstly to complete conversion, then VREF _ HIGH is input to complete conversion, when the input voltage is converted from VREF _ L OW to VREF _ HIGH, the two-point calibration is carried out, however, the input temperature is converted from Temp _ L OW to Temp _ HIGH, or the working environment of Temp _ L OW is converted to the working environment of Temp _ HIGH, or the current working environment temperature is increased from Temp _ L OW to Temp _ HIGH, the two modes are very complicated, the actual operation is not easy, particularly, all chips need to be subjected to temperature conversion after one time, and then the temperature is converted to Temp _ L OW to Temp _ HIGH, and the back-and forth calibration is caused, so that the cost of the chip calibration is greatly increased.
In addition, two paths of voltage-current conversion and two paths of delay circuits exist in the scheme, so that the power consumption and the area of the chip are increased, and the cost is also influenced.
Another prior art patent: a temperature sensor integrated in an RFID tag (application publication No. CN 106017730A) and the just mentioned low-voltage low-power consumption CMOS temperature sensor (application publication No. CN 102338669 a) have similar disadvantages.
In addition, in the prior art, the function of the temperature is complex, and the accuracy is easily influenced by the deviation of the MOS process. It is well known that MOS process variation is large and bipolar process variation is small. So it will be described below that the present invention implements the temperature function using bipolar.
In the prior art, the precision can only be compensated by double-point calibration after the tape-out, but the double-point calibration operation is complicated, and the cost of a chip can be greatly increased.
Therefore, it is necessary to design a temperature sensor and a temperature sensing method.
Disclosure of Invention
The invention aims to provide a temperature sensor and a temperature sensing method, which are easy to implement and convenient to use.
The technical solution of the invention is as follows:
a temperature sensor is characterized by comprising a current source, a triode (Q1), an MOS (M1A), a comparator, a NAND gate and an RS flip-flop (FF 1); the triode is a PNP type triode, and the MOS tube is an N-channel MOS tube;
the temperature sensor also comprises an enable terminal EN, an enable terminal START and an output terminal Dout;
(1) a first output end (Iptat1) of the current source is connected with the e pole of the triode, and the b pole and the c pole of the triode are both grounded;
(2) the second output end (Iptat2) of the current source is connected with the D pole of the MOS tube; the S pole of the MOS tube is grounded, and the START end START is connected with the G pole of the MOS tube through the NOT gate; the second output terminal (Iptat2) of the current source is grounded via a capacitor C1;
(3) the e pole of the triode is connected with the non-inverting input end of the comparator; the D pole of the MOS tube is connected with the inverting input end of the comparator;
(4) the enable input end of the current source and the first input end of the NAND gate are connected with an enable end EN, and the output end of the comparator is connected with the second input end of the NAND gate; the output end of the NAND gate is connected with the R end of the RS trigger;
(5) the START end START is connected with the S end of the RS trigger through a buffer; and the Q end of the RS trigger is connected with the input end PW of the digital control and calculator.
The current source is a PTAT current source.
The current source comprises an operational amplifier, 2 triodes and 4 JFET tubes;
the 2 triodes are Q1 and Q2 respectively and are PNP type triodes; the 4 JFET tubes are M1-M4 and are PMOS-JFET tubes;
recording VDD as a direct current voltage supply end;
s poles of the 4 PMOS-JFET tubes are connected with a VDD end; g electrodes of the 4 JFET tubes are all connected with the output end of the operational amplifier;
d poles of M1 and M2 are respectively connected with a non-inverting input end and an inverting input end of the operational amplifier, and D poles of M3 and M4 are respectively 2 output ends of the current source;
the D pole of M1 is connected with the e pole of transistor Q1 through resistor R1; the b pole and the c pole of the triode Q1 are both grounded;
the D pole of M2 is connected with the e pole of transistor Q2; the b and c poles of transistor Q2 are both connected to ground.
The temperature sensor also comprises a digital control and counter, and the PW, EN and START are all connected with the digital control and counter;
the digital control and calculator is also connected to an OSC oscillator.
Note TPWThe pulse width of the PW signal is changed along with the temperature, and different pulse widths correspond to different temperatures; t isOSCOutputting clock C L K period for OSC oscillator, and using clock C L K of OSC to clock T in digital control and counterPWCounting to obtain Data, and obtaining Dout through a calibration algorithm, wherein Dout represents a centigrade temperature value obtained through testing;
comprises the following steps:
Dout＝T_trim-(Data-Data_trim)/param；
wherein K is coefficient, and has K-R1C 1/ln 4/(R)OSCCOSC)；
Rosc is the resistance of the OSC oscillator; cosc is the capacitance of the OSC oscillator;
VBE is the voltage difference between the b level and the e level in the triode;
VT is the thermoelectric potential, a physical constant proportional to temperature,VT＝kT/qwherein K is Boltzmann's constant, and is 1.38 × 10^ (-23) J/K, "^" represents power or power, T is thermodynamic temperature, namely absolute temperature, q is electronic charge (1.6 × 10^ (-19) C), at normal temperature,VTequal to 26 mV.
T _ trim and Data _ trim respectively represent values of the characterization temperature measured by the chip at the calibration temperature and the calibration temperature, Data is a value measured by the chip at the current temperature when the chip is used, and param is a constant parameter;
a temperature sensing method adopts the temperature sensor to acquire temperature data.
Has the advantages that:
the temperature sensor and the temperature sensing method of the invention are characterized in that two signals related to temperature are: VBE and Iptat utilize a comparator to convert voltage pulse, reduce circuit complexity, scale and consumption, also be favorable to the improvement of precision simultaneously. The voltage pulse is quantized to a temperature value according to the voltage pulse width in the time domain. The voltage pulse width and the quantization clock are both proportional to the same RC, and the influence of the RC process angle on the precision is reduced.
The concrete formula is as follows:
Drawings
FIG. 1 is a general electrical schematic of a temperature sensor;
FIG. 2 is a detailed waveform diagram;
FIG. 3 is a schematic diagram of a PTAT current source;
FIG. 4 is a graph of simulated error for a temperature sensor at a plurality of process corners, common, extreme, etc., after calibration at-5 ℃;
FIG. 5 is a schematic diagram of an RS flip-flop;
FIG. 6 is a graph of simulated error for a temperature sensor at several process corners common after a single point calibration at 90 deg.C.
Detailed Description
The invention will be described in further detail below with reference to the following figures and specific examples:
example 1a block diagram of a whole Temperature Sensor (TS) is shown in fig. 1, where EN is an enable signal of the whole temperature sensor, EN is 0 to turn off TS, and EN is 1 TS to operate, START is a temperature measurement enable signal of the temperature sensor, TS does not measure temperature when START is 0, START is 1 to set FF1 output, TS STARTs temperature measurement, PW is an output signal whose pulse width is temperature-modulated, PW is set to 1 when START is 1, temperature measurement STARTs, after a certain time (which varies with temperature), the comparator output flips to 0, and FF1 is reset so that the pulse width (pulse width) at which PW becomes 0. PW high level is counted by a clock C L K of an OSC oscillator in a digital counter, thereby calculating the current temperature.
The waveform of a typical operation is as follows: (1) in the initial state, EN is START 0, R is 1, S is 0, and FF1 resets the output PW to 0.
(2) EN 1 PTAT current starts working, and two PTAT currents are provided down to Q1, C1& M1, respectively. Transistor Q1 generates reference voltage VBE. At this time, START is 0, switch (switch) M1A is open, the current flows to ground through M1A, VRAMP is 0, comparator output cmp _ out is high, R is changed from 1 to 0, S is maintained at 0, FF1 maintains 0 because R is 0.
(3) START 1 indicates that the temperature is measured from now on. When S is 1, FF1 output PW is set to 1, switch M1A is turned off, PTAT current charges capacitor C1, and VRAMP ramps up slowly from 0.
(4) When VRAMP climbs to be greater than the reference voltage VBE, the comparator output cmp _ out changes from 1 to 0, R correspondingly changes from 0 to 1, FF1 is reset, FF1 outputs PW that changes from 1 to 0, and the pulse width of the output PW contains information of the current temperature. After a certain delay, START goes to 0, switch M1A is opened to discharge VRAMP to 0 in preparation for the next measurement. See figure 2 for specific waveforms.
The PTAT current source in fig. 1 employs the structure in a common bandgap reference, as shown in fig. 3. M1-M4 are the same, Q1 is n times Q2, n is a positive integer, and the size refers to the size of these devices during manufacturing, for example, in an actual circuit, n is 4, the voltage drop across the resistor R1 in fig. 3 is:
ΔVBE＝VBE_Q2-VBE_Q1＝VTln n
so that the current Iptat＝ΔVBE/R1＝VTln n/R1
The OSC oscillator of FIG. 1 uses a conventional ring oscillator that charges a capacitor with current, known as the oscillator output clock C L K cycle TOSC：TOSC∝ROSCCOSC
The Iptat current in fig. 1 charges the capacitor C1, and the PW pulse width can be expressed as:
so counting the PW with OSC can be expressed as:
wherein K is R1C 1/ln 4/(R)OSCCOSC) The resistor R1 in the PTAT current source and the resistor Rosc of the oscillator are the same type of resistor, and the ratio of the two is a fixed constant. The charging/discharging capacitor C1 is the same as the oscillator resistor Rosc, so K is a constant. In this case, the first and second liquid crystal display panels,
with VBE and V onlyTIn this connection, the VBE molecule is dependent on temperatureRising and falling in degree, denominator VTIs increased with the temperature rise, so
Is a function of temperature and can well represent the temperature. More importantly, the process angle of the MOS device is basically irrelevant, and only the VBE process angle of bipolar is relevant. Since bipolar has much smaller process angle variation than MOS, it is very difficult to reduce the process angle variation
The advantage of being relatively easy to calibrate for measuring temperature. The simulation errors for various process corner combinations after calibration at-5 ℃ in the present example are shown in FIG. 4 below.
In fig. 4, C1-C9 represent different process corners (corner), and the device under each process corner (corner) is as follows:
all circuits in the embodiment of the invention work under the voltage of 1V, the current of all current branches is at nA level, the typical power consumption is 460nW, and only 1nJ of electric quantity is needed for one-time temperature measurement.
The VBE in the present embodiment is a PNP transistor, which is convenient for compatibility with CMOS process. Other devices can be realized, such as pn junction voltage of a diode, an NPN tube and the like.
Chopping (chopper) can be added into the comparator, so that the influence of offset voltage (Vos) on the precision is reduced, and the precision is further improved.
In the embodiment of the invention, the temperature sensor is designed based on the GSMC 0.13um L P process, and the calibration algorithm comprises the following steps:
Dout＝T_trim-(Data-Data_trim)/ param
t _ trim and Data _ trim respectively represent values of the calibration temperature and the characterization temperature measured by the chip at the calibration temperature, Data is a value measured by the chip at the current temperature when the chip is used, Dout represents a current temperature value obtained according to a calibration algorithm, and param is a constant parameter. The temperature range was-10 ℃ to 30 ℃ with a-5 ℃ single point calibration with param equal to 6.2 and error as shown in fig. 4. If the temperature measurement range is other range, the same level of precision can be obtained by changing the calibration point from-5 ℃ to other temperature. For example, when the temperature measurement range is 85 ℃ to 125 ℃, single-point calibration at 90 ℃ is adopted, param is equal to 3.61, and the measurement error is shown in fig. 6; C1-C4 in FIG. 6 represent different process corners (corner), and the device under each process corner (corner) is specifically as follows:
from FIG. 6, it is clear that the error is within 1 ℃.
Claims (4)
1. A temperature sensor is characterized by comprising a current source, a triode (Q1), an MOS (M1A), a comparator, a NAND gate and an RS flip-flop (FF 1); the triode is a PNP type triode, and the MOS tube is an N-channel MOS tube;
the temperature sensor also comprises an enable end EN, an enable end START and an output end PW;
(1) a first output end (Iptat1) of the current source is connected with the e pole of the triode, and the b pole and the c pole of the triode are both grounded;
(2) the second output end (Iptat2) of the current source is connected with the D pole of the MOS tube; the S pole of the MOS tube is grounded, and the START end START is connected with the G pole of the MOS tube through the NOT gate; the second output terminal (Iptat2) of the current source is grounded via a capacitor C1;
(3) the e pole of the triode is connected with the non-inverting input end of the comparator; the D pole of the MOS tube is connected with the inverting input end of the comparator;
(4) the enable input end of the current source and the first input end of the NAND gate are connected with an enable end EN, and the output end of the comparator is connected with the second input end of the NAND gate; the output end of the NAND gate is connected with the R end of the RS trigger;
(5) the START end START is connected with the S end of the RS trigger through a buffer; the Q end of the RS trigger is connected with the input end PW of the digital control and calculator;
the PW, EN and START are all connected with the digital control and calculator; the digital control and calculator is also connected with an OSC oscillator;
note TPWThe pulse width of the PW signal is changed along with the temperature, and different pulse widths correspond to different temperatures; t isOSCOutputting clock C L K period for OSC oscillator, and using clock C L K of OSC to clock T in digital control and counterPWCounting to obtain Data, and obtaining Dout through a calibration algorithm, wherein Dout represents a centigrade temperature value obtained by testing and comprises the following steps:
Dout＝T_trim-(Data—Data_trim)/param
wherein K is coefficient, and has K-R1C 1/ln 4/(R)OSCCOSC)；
Rosc is the resistance of the OSC oscillator; cosc is the capacitance of the OSC oscillator;
VBE is the voltage difference between the b level and the e level in the triode;
VT is the thermoelectric potential, a physical constant proportional to temperature, TV＝kTand/q, where K is Boltzmann's constant, taken as 1.38 × 10^ 10 (-23) J/K, "^" indicating power, T is thermodynamic temperature, i.e., absolute temperature, q is electronic charge (1.6 × 10^ (-19) C), at ambient temperature, TVequal to 26 mV;
t _ trim and Data _ trim respectively represent values of the characterization temperature measured by the chip at the calibration temperature and the calibration temperature, Data is a value measured at the current temperature when the chip is used, and param is a constant parameter.
2. The temperature sensor of claim 1, wherein the current source is a PTAT current source.
3. The temperature sensor of claim 2, wherein the current source comprises an operational amplifier, 2 transistors and 4 JFET tubes;
the 2 triodes are Q1 and Q2 respectively and are PNP type triodes; the 4 JFET tubes are M1-M4 and are PMOS-JFET tubes;
recording VDD as a direct current voltage supply end;
s poles of the 4 PMOS-JFET tubes are connected with a VDD end; g electrodes of the 4 JFET tubes are all connected with the output end of the operational amplifier;
d poles of M1 and M2 are respectively connected with a non-inverting input end and an inverting input end of the operational amplifier, and D poles of M3 and M4 are respectively 2 output ends of the current source;
the D pole of M1 is connected with the e pole of transistor Q1 through resistor R1; the b pole and the c pole of the triode Q1 are both grounded;
the D pole of M2 is connected with the e pole of transistor Q2; the b and c poles of transistor Q2 are both connected to ground.
4. A method of temperature sensing, wherein temperature data is acquired using the temperature sensor of any one of claims 1-3.
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