IPC분류정보
국가/구분 |
United States(US) Patent
등록
|
국제특허분류(IPC7판) |
|
출원번호 |
US-0205231
(2005-08-15)
|
발명자
/ 주소 |
|
출원인 / 주소 |
|
대리인 / 주소 |
|
인용정보 |
피인용 횟수 :
4 인용 특허 :
6 |
초록
▼
A current source for providing a current proportional to absolute temperature (a PTAT current) with high precision is implemented using only one off-chip component. The current source utilizes a bandgap voltage, a voltage related to a current proportional to absolute temperature and a constant curre
A current source for providing a current proportional to absolute temperature (a PTAT current) with high precision is implemented using only one off-chip component. The current source utilizes a bandgap voltage, a voltage related to a current proportional to absolute temperature and a constant current to bias a pair of voltage controlled resistive devices. In operation, a known resistance is derived by applying a constant voltage across and a constant current through a first voltage controlled resistive device. A control voltage for maintaining the constant current through the first voltage controlled resistive device is applied to control the second voltage controlled resistive device, thereby generating the highly precise PTAT current at the second voltage controlled resistive device. In one embodiment, the current source uses only one off-chip resistor in a constant current source for generating the constant current.
대표청구항
▼
I claim: 1. A current source circuit providing an output current being proportional to absolute temperature, the circuit comprising: a first transistor and a first resistor connected in series between a positive power supply voltage and a ground voltage, the first transistor having a control termin
I claim: 1. A current source circuit providing an output current being proportional to absolute temperature, the circuit comprising: a first transistor and a first resistor connected in series between a positive power supply voltage and a ground voltage, the first transistor having a control terminal coupled to a first voltage related to a current proportional to absolute temperature to cause a current proportional to absolute temperature to flow through the first transistor and the first resistor, a second voltage being a voltage proportional to absolute temperature being developed at a first node between the first transistor and the first resistor; a first voltage-current buffering circuit having a first terminal coupled to receive the second voltage, a second terminal providing a third voltage being a buffered voltage of the second voltage, and a third terminal providing the output current proportional to absolute temperature, the output current being equal to a current flowing in the second terminal; a first voltage controlled resistive device having a first terminal coupled to the second terminal of the first voltage-current buffering circuit, a second terminal coupled to the ground voltage and a voltage control terminal receiving a control voltage; a constant voltage circuit receiving a bandgap voltage as an input voltage at an input terminal, the constant voltage circuit comprising an output stage providing a fourth voltage being a buffered voltage of a fifth voltage related to the bandgap voltage at a first output terminal and providing a second output current at a second output terminal; a second voltage controlled resistive device having a first terminal coupled to the first output terminal of the constant voltage circuit, a second terminal coupled to the ground voltage and a voltage control terminal receiving the control voltage, the second voltage controlled resistive device matching the first voltage controlled resistive device; a first current mirror mirroring the second output current of the constant voltage circuit and supplying the mirrored current to a second resistor; a third resistor matching the second resistor and being supplied by a first constant current; and a comparator receiving a voltage across the second resistor and a voltage across the third resistor, the comparator generating the control voltage for controlling the resistance of the first and second voltage controlled resistive devices, the control voltage being generated to force the voltage across the second resistor to equal to the voltage across the third resistor. 2. The current source circuit of claim 1, further comprising: a bandgap reference circuit providing the bandgap voltage and the first voltage related a current proportional to absolute temperature, the bandgap reference circuit comprising a second current mirror providing the current proportional to absolute temperature, the first voltage being a bias voltage of the current mirror. 3. The current source circuit of claim 2, wherein the first transistor comprises a PMOS transistor having a gate terminal coupled to the first voltage, a drain terminal coupled to the first node and a source terminal coupled to the positive power supply voltage, the first transistor forming a current mirror with the second current mirror of the bandgap reference circuit for mirroring the current proportional to absolute temperature using the first voltage. 4. The current source circuit of claim 2, further comprising: a constant current source receiving the bandgap voltage from the bandgap reference circuit and generating the first constant current, the constant current source adapted to apply a buffered voltage of the bandgap voltage to a fourth resistor to cause a constant current to flow through the fourth resistor, the constant current source further comprising a current mirror for mirroring the constant current flowing through the fourth resistor as the first constant current. 5. The current source circuit of claim 4, wherein the fourth resistor is an off-chip resistor formed outside of the integrated circuit on which the current source circuit is formed. 6. The current source circuit of claim 1, wherein the first voltage-current buffering circuit comprises: a first operational amplifier having a positive input terminal being the first terminal, a negative input terminal being the second terminal, and an output terminal providing a voltage indicative of the difference between the voltages at the positive input terminal and the negative input terminal; and a second transistor having a control terminal coupled to the output terminal of the first operational amplifier, a first current handling terminal being the second terminal providing the third voltage and a second current handling terminal being the third terminal providing the output current proportional to absolute temperature. 7. The current source circuit of claim 1, wherein: the first voltage controlled resistive device comprises a third transistor having a control terminal coupled to the control voltage, a first current handling terminal coupled to the second terminal of the first voltage-current buffering circuit and a second current handling terminal coupled to the ground voltage; and the second voltage controlled resistive device comprises a fourth transistor having a control terminal coupled to the control voltage, a first current handling terminal coupled to the first output terminal of the constant voltage circuit and a second current handling terminal coupled to the ground voltage, wherein the third transistor and the fourth transistor are matching transistor devices. 8. The current source circuit of claim 1, wherein the constant voltage circuit comprises: a second operational amplifier having a positive input terminal coupled to receive the bandgap voltage, a negative input terminal and an output terminal providing a sixth voltage being a buffered voltage of the bandgap voltage; a third operational amplifier having a positive input terminal coupled to receive the fifth voltage derived from the sixth voltage, a negative input terminal being the second output node, and an output terminal providing a voltage indicative of the difference between the voltages at the positive input terminal and the negative input terminal; and a fifth transistor being the output stage, the fifth transistor having a control terminal coupled to the output terminal of the third operational amplifier, a first current handling terminal being the first output terminal providing the fourth voltage and a second current handling terminal being the second output terminal. 9. The current source circuit of claim 8, wherein the constant voltage circuit further comprises a voltage divider coupled between the output terminal of the second operational amplifier and the ground voltage, the voltage divider adapted to divide down the sixth voltage to generate the fifth voltage, the fifth voltage being a divided down voltage of the bandgap voltage. 10. The current source circuit of claim 9, wherein the fifth voltage is one third of the bandgap voltage. 11. The current source circuit of claim 1, wherein the comparator comprises a fourth operational amplifier having a positive input terminal coupled to receive the voltage across the third resistor, a negative input terminal coupled to receive the voltage across the second resistor and an output terminal providing the control voltage. 12. A method for generating a current proportional to absolute temperature, comprising: generating a first voltage proportional to absolute temperature on a first node; buffering the first voltage to generate a second voltage on a second node; coupling a first voltage controlled resistive device to the second node, the resistance value of the first voltage controlled resistive device being controlled by a control voltage, wherein a current flowing through the second node is the current proportional to absolute temperature; generating a third voltage at a third node from a bandgap voltage, the third voltage having a constant voltage value; coupling a second voltage controlled resistive device to the third node, the resistance value of the second voltage controlled resistive device being controlled by the control voltage, the second voltage controlled resistive device matching the first voltage controlled resistive device; mirroring a current flowing through the second voltage controlled resistive device to flow through a first resistor; flowing a constant current through a second resistor, the first resistor and the second resistor being matching resistive devices; and comparing a voltage across the first resistor and a voltage across the second resistor to generate the control voltage. 13. The method of claim 12, further comprising: generating the bandgap voltage using a bandgap reference circuit, the bandgap reference circuit including a fourth voltage related to a current proportional to absolute temperature; coupling the fourth voltage to a current mirror to generate a first current that is proportional to absolute temperature; and flowing the first current through a third resistor to generate the first voltage. 14. The method of claim 12, wherein generating the third voltage at the third node from a bandgap voltage comprises: buffering the bandgap voltage to generate a fifth voltage on a fourth node; generating a sixth voltage derived from the fifth voltage; and buffering the sixth voltage to generate the third voltage at the third node. 15. The method of claim 14, wherein generating a sixth voltage derived from the fifth voltage comprises dividing down the fifth voltage to generate the sixth voltage. 16. The method of claim 15, wherein the sixth voltage is one third of the fifth voltage.
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