CN101762338B - Temperature sensor circuit and temperature signal processing method - Google Patents

Abstract

The invention discloses a temperature sensor circuit, which includes a temperature sensing part, and a temperature signal conversion part; the temperature sensing part includes three current source circuits connected between a power end and the earth in parallel; the temperature signal conversion part includes a multiplexer, and an A/D converter; the multiplexer is provided with three signal input ends which are respectively connected with the bipolar transistors in each current source circuit; and the voltage output end of the multiplexer is connected with the analog signal input end of the A/D converter. The invention also provides a temperature signal processing method realized by the circuit; and the value of the temperature signal is obtained through the voltage values in the three current source circuits. The invention generates a voltage VPTAT proportional to an absolute temperature by calculating three generated base emitter voltages VBE1, VBE2 and VBE3, which can compensate the influence of the equivalent series resistances of the bipolar transistors, thereby leading VPTAT to more approach to an ideal value, and being proportional to the absolute temperature, thus greatly improving the precision of the temperature sensor circuit.

Description

Temperature sensor circuit and temperature signal processing method

Technical field

The present invention relates to a kind of temperature sensor circuit.The invention still further relates to the method that a kind of temperature sensor circuit is handled temperature signal.

Background technology

Existing temperature sensor circuit as shown in Figure 1, comprise temperature sensing part and temperature signal conversion portion, described temperature sensing comprises that partly two-way is connected in parallel on the current source circuit between power end VDD and the ground VSS, described every road current source circuit comprises a current source and a bipolar transistor, Q4 as shown in Figure 1 or Q5, one end of described current source connects power end, the other end connects the emitter of described bipolar transistor, it is by the emitter of power end to bipolar transistor that described current source produces sense of current, and the collector of described bipolar transistor is connected with base stage and ground connection; Described temperature signal conversion portion comprises a multiplexer and an analog to digital converter, described multiplexer has two signal input parts, the emitter that connects the bipolar transistor in each current source circuit respectively, the voltage output end of described multiplexer connect the input end of analog signal V of described analog to digital converter _IN

Described emitter bipolar transistor produces voltage VBE4 and the VBE5 that is inversely proportional to absolute temperature, by the temperature signal conversion portion that voltage multiplexer and analog to digital converter constitute, the voltage signal relevant with temperature is converted to the digital signal of expression environment temperature.

According to the characteristic of bipolar transistor as can be known:

$\mathrm{VBE}4=\frac{\mathrm{kT}}{q}\left(\ln \frac{I}{I_S}\right)+I\·\mathrm{RS}$

$\mathrm{VBE}5=\frac{\mathrm{kT}}{q}\left(\ln \frac{\mathrm{pI}}{I_S}\right)+\mathrm{pI}\·\mathrm{RS}$

Wherein, k is a Boltzmann constant, is 1.38 * 10 ^-23J/K, T are absolute temperature, and q is the unit electron charge, are 1.6 * 10 ^-19C, I are the collector currents of bipolar transistor Q4, and Is is the saturation current of bipolar transistor, and RS is the equivalent series resistance of bipolar transistor Q4 and Q5, and p is the multiplying power of Q5 collector current size to Q4 collector current size.

The temperature signal conversion portion at first converts VBE4 and VBE5 and the proportional voltage VPTAT of absolute temperature to, and and the irrelevant reference voltage V REF of temperature.

$\mathrm{VPTAT}=\mathrm{VBE}5-\mathrm{VBE}4=\frac{\mathrm{kT}}{q}\ln$

VREF＝VBE4+α·VPTAT；

Wherein α is a scale-up factor, and numerical value is determined by device property, and the temperature coefficient of VBE4 and the temperature coefficient of α VPTAT are cancelled each other, thus the irrelevant voltage VREF of generation and temperature;

ADC output digital temperature signal is:

${\mathrm{AD}}_{\mathrm{OUT}}=\frac{\mathrm{VPTAT}}{\mathrm{VREF}}.$

Because there is equivalent series resistance RS in bipolar transistor, so VPTAT is not complete and absolute temperature is directly proportional, but a fixing imbalance is arranged, therefore produced thermometric error.

Summary of the invention

Technical matters to be solved by this invention provides a kind of temperature sensor circuit, and a kind of temperature sensor circuit method that temperature signal is handled, can adopt comparatively simple circuit configuration, improves the measuring accuracy of temperature sensor circuit.

For solving the problems of the technologies described above, the technical scheme of temperature sensor circuit of the present invention is, comprise temperature sensing part and temperature signal conversion portion, described temperature sensing comprises that partly three the tunnel are connected in parallel on the current source circuit between power end and the ground, described every road current source circuit comprises a current source and a PNP pipe, one end of described current source connects power end, the other end connects the emitter of described PNP pipe, it is by the emitter of power end to the PNP pipe that described current source produces sense of current, and the collector of described PNP pipe is connected with base stage and ground connection; Described temperature signal conversion portion comprises a multiplexer and an analog to digital converter, described multiplexer has three signal input parts, the emitter that connects the PNP pipe in each current source circuit respectively, the voltage output end of described multiplexer connects the input end of analog signal of described analog to digital converter.

The technical scheme of temperature signal processing method of the present invention is, described multiplexer is gathered the voltage signal in the current source circuit, and the voltage signal in three road current source circuits is respectively:

$\mathrm{<figure-callout\; id="1"\; label="VBE"\; filenames="H2008100441687E00012.png"\; state="\{\{state\}\}">VBE</figure-callout>}1=\frac{\mathrm{kT}}{q}\left(\ln \frac{I_1}{I_{S1}}\right)+{\mathrm{<figure-callout\; id="1"\; label="I"\; filenames="H2008100441687E00012.png"\; state="\{\{state\}\}">I</figure-callout>}}_1\&CenterDot;\mathrm{<figure-callout\; id="1"\; label="RS"\; filenames="H2008100441687E00012.png"\; state="\{\{state\}\}">RS</figure-callout>}1;$

$\mathrm{VBE}2=\frac{\mathrm{kT}}{q}\left(\ln \frac{m_1{I}_1}{I_{S1}}\right)+m_1{\mathrm{<figure-callout\; id="1"\; label="I"\; filenames="H2008100441687E00012.png"\; state="\{\{state\}\}">I</figure-callout>}}_1\&CenterDot;\mathrm{<figure-callout\; id="1"\; label="RS"\; filenames="H2008100441687E00012.png"\; state="\{\{state\}\}">RS</figure-callout>}1;$

$\mathrm{VBE}3=\frac{\mathrm{kT}}{q}\left(\ln \frac{n_1{I}_1}{I_{S1}}\right)+n_1{\mathrm{<figure-callout\; id="1"\; label="I"\; filenames="H2008100441687E00012.png"\; state="\{\{state\}\}">I</figure-callout>}}_1\&CenterDot;\mathrm{<figure-callout\; id="1"\; label="RS"\; filenames="H2008100441687E00012.png"\; state="\{\{state\}\}">RS</figure-callout>}1;$

Wherein, k is a Boltzmann constant, and T is an absolute temperature, and q is the unit electron charge, I ₁Be the collector current of PNP pipe in the first via current source circuit, I _S1Be the saturation current of PNP pipe, RS1 is the equivalent series resistance of PNP pipe, m ₁Be the scale-up factor of the collector current of PNP pipe in the second road current source circuit with respect to the collector current of PNP pipe in the first via current source circuit; n ₁Be the scale-up factor of the collector current of PNP pipe in the Third Road current source circuit with respect to the collector current of PNP pipe in the first via current source circuit;

Described multiplexer converts VBE1, VBE2 and VBE3 and the proportional voltage VPTAT of absolute temperature to, and and the irrelevant reference voltage V REF of temperature,

$\mathrm{VPTAT}=(n_1-1)(\mathrm{VBE}2-\mathrm{VBE}1)-(m_1-1)(\mathrm{VBE}3-\mathrm{VBE}1)=\frac{\mathrm{kT}}{q}\ln \left(\frac{{m_1}^{n_1-1}}{{n_1}^{m_1-1}}\right);$

VREF＝VBE1+α·VPTAT；

Wherein α is a scale-up factor, and numerical value is determined by device property, and the temperature coefficient of VBE1 and the temperature coefficient of α VPTAT are cancelled each other, thus the irrelevant voltage VREF of generation and temperature;

Afterwards, the output signal value of described analog to digital converter is:

${\mathrm{AD}}_{\mathrm{OUT}}=\frac{\mathrm{VPTAT}}{\mathrm{VREF}}.$

The another kind of technical scheme of a kind of temperature sensor circuit of the present invention is, comprise temperature sensing part and temperature signal conversion portion, described temperature sensing comprises that partly three the tunnel are connected in parallel on the current source circuit between power end and the ground, described every road current source circuit comprises a current source and a NPN pipe, one end of described current source connects power end, the other end connects the collector of described NPN pipe, it is by the collector of power end to the NPN pipe that described current source produces sense of current, the collector of described NPN pipe is connected with base stage, the grounded emitter of described NPN pipe; Described temperature signal conversion portion comprises a multiplexer and an analog to digital converter, described multiplexer has three signal input parts, the collector that connects the NPN pipe in each current source circuit respectively, the voltage output end of described multiplexer connects the input end of analog signal of described analog to digital converter.

The another kind of technical scheme of temperature signal processing method of the present invention is, described multiplexer is gathered the voltage signal in the current source circuit, and the voltage signal in three road current source circuits is respectively:

$\mathrm{<figure-callout\; id="1"\; label="VBE"\; filenames="H2008100441687E00012.png"\; state="\{\{state\}\}">VBE</figure-callout>}1=\frac{\mathrm{kT}}{q}\left(\ln \frac{I_2}{I_{S2}}\right)+I_2\&CenterDot;\mathrm{RS}2;$

$\mathrm{VBE}2=\frac{\mathrm{kT}}{q}\left(\ln \frac{m_2{I}_2}{I_{S2}}\right)+m_2{I}_2\&CenterDot;\mathrm{RS}2;$

$\mathrm{VBE}3=\frac{\mathrm{kT}}{q}\left(\ln \frac{n_2{I}_2}{I_{S2}}\right)+n_2{I}_2\&CenterDot;\mathrm{RS}2;$

Wherein, k is a Boltzmann constant, and T is an absolute temperature, and q is the unit electron charge, I ₂Be the collector current of NPN pipe in the first via current source circuit, I _S2Be the saturation current of NPN pipe, RS2 is the equivalent series resistance of NPN pipe, m ₂Be the scale-up factor of the collector current of NPN pipe in the second road current source circuit with respect to the collector current of NPN pipe in the first via current source circuit; n ₂Be the scale-up factor of the collector current of NPN pipe in the Third Road current source circuit with respect to the collector current of NPN pipe in the first via current source circuit;

Described multiplexer converts VBE1, VBE2 and VBE3 and the proportional voltage VPTAT of absolute temperature to, and and the irrelevant reference voltage V REF of temperature,

$\mathrm{VPTAT}=(n_2-1)(\mathrm{VBE}2-\mathrm{VBE}1)-(m_2-1)(\mathrm{VBE}3-\mathrm{VBE}1)=\frac{\mathrm{kT}}{q}\ln \left(\frac{{m_2}^{n_2-1}}{{n_2}^{m_2-1}}\right);$

VREF＝VBE1+α·VPTAT；

Wherein α is a scale-up factor, and numerical value is determined by device property, and the temperature coefficient of VBE1 and the temperature coefficient of α VPTAT are cancelled each other, thus the irrelevant voltage VREF of generation and temperature;

Afterwards, the output signal value of described analog to digital converter is:

${\mathrm{AD}}_{\mathrm{OUT}}=\frac{\mathrm{VPTAT}}{\mathrm{VREF}}.$

The present invention makes circuit structure still comparatively simple by having added the 3rd current source circuit, has improved the precision of temperature sensor circuit simultaneously greatly.

Description of drawings

The present invention is further detailed explanation below in conjunction with drawings and Examples:

Fig. 1 is the circuit diagram of existing temperature sensor circuit;

Fig. 2 and Fig. 3 are the circuit diagram of temperature sensor circuit of the present invention.

Embodiment

The invention discloses a kind of temperature sensor circuit, as shown in Figure 2, comprise temperature sensing part and temperature signal conversion portion, described temperature sensing comprises that partly three the tunnel are connected in parallel on the current source circuit between power end VDD and the ground VSS, described every road current source circuit comprises a current source and a PNP pipe, Q1 as shown in Figure 2, Q2 or Q3, one end of described current source connects power end, the other end connects the emitter of described PNP pipe, it is by the emitter of power end to the PNP pipe that described current source produces sense of current, and the collector of described PNP pipe is connected with base stage and ground connection; Described temperature signal conversion portion comprises a multiplexer and an analog to digital converter, described multiplexer has three signal input parts, the emitter that connects the PNP pipe in each current source circuit respectively, the voltage output end of described multiplexer connect the input end of analog signal V of described analog to digital converter _IN

The present invention also provides a kind of temperature signal processing method that adopts the said temperature sensor circuit to realize, described multiplexer is gathered the voltage signal in the current source circuit, and the voltage signal in three road current source circuits is respectively:

$\mathrm{<figure-callout\; id="1"\; label="VBE"\; filenames="H2008100441687E00012.png"\; state="\{\{state\}\}">VBE</figure-callout>}1=\frac{\mathrm{kT}}{q}\left(\ln \frac{I_1}{I_{S1}}\right)+{\mathrm{<figure-callout\; id="1"\; label="I"\; filenames="H2008100441687E00012.png"\; state="\{\{state\}\}">I</figure-callout>}}_1\&CenterDot;\mathrm{<figure-callout\; id="1"\; label="RS"\; filenames="H2008100441687E00012.png"\; state="\{\{state\}\}">RS</figure-callout>}1;$

$\mathrm{VBE}2=\frac{\mathrm{kT}}{q}\left(\ln \frac{m_1{I}_1}{I_{S1}}\right)+m_1{\mathrm{<figure-callout\; id="1"\; label="I"\; filenames="H2008100441687E00012.png"\; state="\{\{state\}\}">I</figure-callout>}}_1\&CenterDot;\mathrm{<figure-callout\; id="1"\; label="RS"\; filenames="H2008100441687E00012.png"\; state="\{\{state\}\}">RS</figure-callout>}1;$

$\mathrm{VBE}3=\frac{\mathrm{kT}}{q}\left(\ln \frac{n_1{I}_1}{I_{S1}}\right)+n_1{\mathrm{<figure-callout\; id="1"\; label="I"\; filenames="H2008100441687E00012.png"\; state="\{\{state\}\}">I</figure-callout>}}_1\&CenterDot;\mathrm{<figure-callout\; id="1"\; label="RS"\; filenames="H2008100441687E00012.png"\; state="\{\{state\}\}">RS</figure-callout>}1;$

Wherein, k is a Boltzmann constant, and T is an absolute temperature, and q is the unit electron charge, I ₁Be the collector current of PNP pipe in the first via current source circuit, I _S1Be the saturation current of PNP pipe, RS1 is the equivalent series resistance of PNP pipe, m ₁Be the scale-up factor of the collector current of PNP pipe in the second road current source circuit with respect to the collector current of PNP pipe in the first via current source circuit; n ₁Be the scale-up factor of the collector current of PNP pipe in the Third Road current source circuit with respect to the collector current of PNP pipe in the first via current source circuit;

Described multiplexer converts VBE1, VBE2 and VBE3 and the proportional voltage VPTAT of absolute temperature to, and and the irrelevant reference voltage V REF of temperature,

$\mathrm{VPTAT}=(n_1-1)(\mathrm{VBE}2-\mathrm{VBE}1)-(m_1-1)(\mathrm{VBE}3-\mathrm{VBE}1)=\frac{\mathrm{kT}}{q}\ln \left(\frac{{m_1}^{n_1-1}}{{n_1}^{m_1-1}}\right);$

VREF＝VBE1+α·VPTAT；

Wherein α is a scale-up factor, and numerical value is determined by device property, and the temperature coefficient of VBE1 and the temperature coefficient of α VPTAT are cancelled each other, thus the irrelevant voltage VREF of generation and temperature;

Afterwards, the output signal value of described analog to digital converter is:

${\mathrm{AD}}_{\mathrm{OUT}}=\frac{\mathrm{VPTAT}}{\mathrm{VREF}}.$

The invention also discloses another kind of temperature sensor circuit, as shown in Figure 3, comprise temperature sensing part and temperature signal conversion portion, it is characterized in that, described temperature sensing comprises that partly three the tunnel are connected in parallel on the current source circuit between power end and the ground, described every road current source circuit comprises a current source and a NPN pipe, one end of described current source connects power end, the other end connects the collector of described NPN pipe, it is by the collector of power end to the NPN pipe that described current source produces sense of current, the collector of described NPN pipe is connected with base stage, the grounded emitter of described NPN pipe; Described temperature signal conversion portion comprises a multiplexer and an analog to digital converter, described multiplexer has three signal input parts, the collector that connects the NPN pipe in each current source circuit respectively, the voltage output end of described multiplexer connects the input end of analog signal of described analog to digital converter.

The present invention also provides a kind of temperature signal processing method that adopts the said temperature sensor circuit to realize, it is characterized in that, described multiplexer is gathered the voltage signal in the current source circuit, and the voltage signal in three road current source circuits is respectively:

$\mathrm{<figure-callout\; id="1"\; label="VBE"\; filenames="H2008100441687E00012.png"\; state="\{\{state\}\}">VBE</figure-callout>}1=\frac{\mathrm{kT}}{q}\left(\ln \frac{I_2}{I_{S2}}\right)+I_2\&CenterDot;\mathrm{RS}2;$

$\mathrm{VBE}2=\frac{\mathrm{kT}}{q}\left(\ln \frac{m_2{I}_2}{I_{S2}}\right)+m_2{I}_2\&CenterDot;\mathrm{RS}2;$

$\mathrm{VBE}3=\frac{\mathrm{kT}}{q}\left(\ln \frac{n_2{I}_2}{I_{S2}}\right)+n_2{I}_2\&CenterDot;\mathrm{RS}2;$

Wherein, k is a Boltzmann constant, and T is an absolute temperature, and q is the unit electron charge, I ₂Be the collector current of NPN pipe in the first via current source circuit, I _S2Be the saturation current of NPN pipe, RS2 is the equivalent series resistance of NPN pipe, m ₂Be the scale-up factor of the collector current of NPN pipe in the second road current source circuit with respect to the collector current of NPN pipe in the first via current source circuit; n ₂Be the scale-up factor of the collector current of NPN pipe in the Third Road current source circuit with respect to the collector current of NPN pipe in the first via current source circuit;

Described multiplexer converts VBE1, VBE2 and VBE3 and the proportional voltage VPTAT of absolute temperature to, and and the irrelevant reference voltage V REF of temperature,

$\mathrm{VPTAT}=(n_2-1)(\mathrm{VBE}2-\mathrm{VBE}1)-(m_2-1)(\mathrm{VBE}3-\mathrm{VBE}1)=\frac{\mathrm{kT}}{q}\ln \left(\frac{{m_2}^{n_2-1}}{{n_2}^{m_2-1}}\right);$

VREF＝VBE1+α·VPTAT；

Wherein α is a scale-up factor, and numerical value is determined by device property, and the temperature coefficient of VBE1 and the temperature coefficient of α VPTAT are cancelled each other, thus the irrelevant voltage VREF of generation and temperature;

Afterwards, the output signal value of described analog to digital converter is:

${\mathrm{AD}}_{\mathrm{OUT}}=\frac{\mathrm{VPTAT}}{\mathrm{VREF}}.$

The present invention produces VPTAT by three base-emitter voltage VBE1, VBE2 producing and VBE3 are carried out computing, can compensate the influence of equivalent series resistance, thereby make VPTAT more approach ideal value, and be directly proportional, improved the precision of temperature sensor circuit greatly with absolute temperature.

Claims (4)

1. temperature sensor circuit, comprise temperature sensing part and temperature signal conversion portion, it is characterized in that, described temperature sensing comprises that partly three the tunnel are connected in parallel on the current source circuit between power end and the ground, described every road current source circuit comprises a current source and a PNP pipe, one end of described current source connects power end, the other end connects the emitter of described PNP pipe, it is by the emitter of power end to the PNP pipe that described current source produces sense of current, and the collector of described PNP pipe is connected with base stage and ground connection; Described temperature signal conversion portion comprises a multiplexer and an analog to digital converter, described multiplexer has three signal input parts, the emitter that connects the PNP pipe in each current source circuit respectively, the voltage output end of described multiplexer connects the input end of analog signal of described analog to digital converter.

2. a temperature signal processing method that adopts temperature sensor circuit as claimed in claim 1 to realize is characterized in that, described multiplexer is gathered the voltage signal in the current source circuit, and the voltage signal in three road current source circuits is respectively:

$\mathrm{VBE}1=\frac{\mathrm{kT}}{q}\left(\ln \frac{I_1}{I_{S1}}\right)+I_1\&CenterDot;\mathrm{RS}1;$

$\mathrm{VBE}2=\frac{\mathrm{kT}}{q}\left(\ln \frac{m_1{I}_1}{I_{S1}}\right)+m_1{I}_1\&CenterDot;\mathrm{RS}1;$

$\mathrm{VBE}3=\frac{\mathrm{kT}}{q}\left(\ln \frac{n_1{I}_1}{I_{S1}}\right)+n_1{I}_1\&CenterDot;\mathrm{RS}1;$

Wherein, k is a Boltzmann constant, and T is an absolute temperature, and q is the unit electron charge, I ₁Be the collector current of PNP pipe in the first via current source circuit, I _S1Be the saturation current of PNP pipe, RS1 is the equivalent series resistance of PNP pipe, m ₁Be the scale-up factor of the collector current of PNP pipe in the second road current source circuit with respect to the collector current of PNP pipe in the first via current source circuit; n ₁Be the scale-up factor of the collector current of PNP pipe in the Third Road current source circuit with respect to the collector current of PNP pipe in the first via current source circuit;

Described multiplexer converts VBE1, VBE2 and VBE3 and the proportional voltage VPTAT of absolute temperature to, and and the irrelevant reference voltage V REF of temperature,

$\mathrm{VPTAT}=(n_1-1)(\mathrm{VBE}2-\mathrm{VBE}1)-(m_1-1)(\mathrm{VBE}3-\mathrm{VBE}1)=\frac{\mathrm{kT}}{q}\ln \left(\frac{{m_1}^{n_1-1}}{{n_1}^{m_1-1}}\right);$

VREF＝VBE1+α·VPTAT；

Wherein α is a scale-up factor, and numerical value is determined by device property, and the temperature coefficient of VBE1 and the temperature coefficient of α VPTAT are cancelled each other, thus the irrelevant voltage VREF of generation and temperature;

Afterwards, the output signal value of described analog to digital converter is:

${\mathrm{AD}}_{\mathrm{OUT}}=\frac{\mathrm{VPTAT}}{\mathrm{VREF}}.$

3. temperature sensor circuit, comprise temperature sensing part and temperature signal conversion portion, it is characterized in that, described temperature sensing comprises that partly three the tunnel are connected in parallel on the current source circuit between power end and the ground, described every road current source circuit comprises a current source and a NPN pipe, one end of described current source connects power end, the other end connects the collector of described NPN pipe, it is by the collector of power end to the NPN pipe that described current source produces sense of current, the collector of described NPN pipe is connected with base stage, the grounded emitter of described NPN pipe; Described temperature signal conversion portion comprises a multiplexer and an analog to digital converter, described multiplexer has three signal input parts, the collector that connects the NPN pipe in each current source circuit respectively, the voltage output end of described multiplexer connects the input end of analog signal of described analog to digital converter.

4. a temperature signal processing method that adopts temperature sensor circuit as claimed in claim 3 to realize is characterized in that, described multiplexer is gathered the voltage signal in the current source circuit, and the voltage signal in three road current source circuits is respectively:

$\mathrm{VBE}1=\frac{\mathrm{kT}}{q}\left(\ln \frac{I_2}{I_{S2}}\right)+I_2\&CenterDot;\mathrm{RS}2;$

$\mathrm{VBE}2=\frac{\mathrm{kT}}{q}\left(\ln \frac{m_2{I}_2}{I_{S2}}\right)+m_2{I}_2\&CenterDot;\mathrm{RS}2;$

$\mathrm{VBE}3=\frac{\mathrm{kT}}{q}\left(\ln \frac{n_2{I}_2}{I_{S2}}\right)+n_2{I}_2\&CenterDot;\mathrm{RS}2;$

Wherein, k is a Boltzmann constant, and T is an absolute temperature, and q is the unit electron charge, I ₂Be the collector current of NPN pipe in the first via current source circuit, I _S2Be the saturation current of NPN pipe, RS2 is the equivalent series resistance of NPN pipe, m ₂Be the scale-up factor of the collector current of NPN pipe in the second road current source circuit with respect to the collector current of NPN pipe in the first via current source circuit; n ₂Be the scale-up factor of the collector current of NPN pipe in the Third Road current source circuit with respect to the collector current of NPN pipe in the first via current source circuit;

Described multiplexer converts VBE1, VBE2 and VBE3 and the proportional voltage VPTAT of absolute temperature to, and and the irrelevant reference voltage V REF of temperature,

$\mathrm{VPTAT}=(n_2-1)(\mathrm{VBE}2-\mathrm{VBE}1)-(m_2-1)(\mathrm{VBE}3-\mathrm{VBE}1)=\frac{\mathrm{kT}}{q}\ln \left(\frac{{m_2}^{n_2-1}}{{n_2}^{m_2-1}}\right);$

VREF＝VBE1+α·VPTAT；

Wherein α is a scale-up factor, and numerical value is determined by device property, and the temperature coefficient of VBE1 and the temperature coefficient of α VPTAT are cancelled each other, thus the irrelevant voltage VREF of generation and temperature;

Afterwards, the output signal value of described analog to digital converter is:

${\mathrm{AD}}_{\mathrm{OUT}}=\frac{\mathrm{VPTAT}}{\mathrm{VREF}}.$

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