Compensation of thermally induced voltage errors
Described embodiments include an integrated circuit for temperature gradient compensation of a bandgap voltage. A bandgap core circuit has a bandgap feedback input, a bandgap adjustment input and a bandgap reference output. A resistor is coupled between the bandgap adjustment input and a ground terminal. An offset and slope correction circuit has an offset correction output that is coupled to the bandgap adjustment input. A signal at the offset correction output is trimmed at an ambient temperature. A thermal error cancellation (TEC) circuit has a TEC output coupled to the bandgap adjustment input. The TEC circuit includes first and second temperature sensors that are located apart from each other. A signal at the TEC output is responsive to temperatures at the first and second temperature sensors. An amplifier has an amplifier input and an amplifier output. The amplifier input is coupled to the bandgap reference output.
1 . An apparatus comprising:
an integrated circuit (IC) including:
a first circuit including a first transistor at a first location of the IC and a second transistor at a second location of the IC, the first circuit configurable to provide a first current responsive to a first temperature difference between the first location and the second location; and
a second circuit including a third transistor at the first location and a fourth transistor at the second location, the second circuit configurable to provide a second current representing a second temperature difference between the first location and the second location, the second temperature difference having an opposite polarity from the first temperature difference.
2 . The apparatus of claim 1 , wherein the IC further includes:
a third circuit configurable to provide a third current as a difference between the first current and the second current, the third current being linearly propositional to first or second temperature differences.
3 . The apparatus of claim 2 , wherein the first transistor has a same area as the fourth transistor, the second transistor has a same area as the third transistor, the first transistor has a different area than the second transistor, and the third transistor has a different area than the fourth transistor.
4 . The apparatus of claim 2 , wherein the third circuit includes a fifth transistor coupled between a reference voltage terminal and the first circuit, and a sixth transistor coupled between the reference voltage terminal and the second circuit, the fifth and sixth transistors forming a current mirror.
5 . The apparatus of claim 1 , wherein the first and second currents are complementary to absolute temperature (CTAT) currents.
6 . The apparatus of claim 2 , further comprising a bandgap reference circuit coupled to an output of the third circuit.
7 . The apparatus of claim 1 , wherein the first and second circuits are each ΔV BE temperature sensor circuits.
8 . The apparatus of claim 6 , wherein the bandgap reference circuit has a bandgap adjustment input, and a bandgap reference output coupled to a reference voltage terminal.
9 . The apparatus of claim 8 , wherein a CTAT current provided at the bandgap adjustment input is combined in the bandgap reference circuit with a proportional to absolute temperature (PTAT) current.
10 . The apparatus of claim 8 , further comprising a resistor coupled between the bandgap adjustment input and a ground terminal.
11 . The apparatus of claim 10 , wherein the bandgap reference circuit is configurable to provide a voltage at the bandgap reference output proportional to a voltage across the resistor.
12 . The apparatus of claim 11 , wherein the voltage at the bandgap reference output is adjusted by changing a current through the resistor.
13 . An integrated circuit comprising:
a voltage reference circuit having a voltage reference terminal and a current terminal;
a first circuit including a first transistor at a first location and a second transistor at a second location, the first circuit configurable to provide a first current response to a first temperature difference between the first location and the second location;
a second circuit including a third transistor at the first location and a fourth transistor at the second location, the second circuit configurable to provide a second current representing a second temperature difference between the first location and the second location, the second temperature difference having an opposite polarity from the first temperature difference; and
a third circuit coupled to the first and second circuits and the current terminal, the third circuit configurable to provide a third current at the current terminal responsive to the first and second currents.
14 . The integrated circuit of claim 13 , wherein the first, second, third, and fourth transistors each include first and second terminals and a control terminal, the first terminal of the first transistor coupled to a first current reference terminal and to the control terminals of the first and second transistors, the first terminal of the third transistor coupled to a second current reference terminal and to the control terminals of the third and fourth transistors, the integrated circuit having a temperature correction output coupled to the first terminal of the fourth transistor, the integrated circuit further comprising:
a first resistor having a first terminal coupled to the second terminal of the first transistor and a second terminal coupled to a ground terminal;
a second resistor having a first terminal coupled to the second terminal of the second transistor and a second terminal coupled to the ground terminal;
a third transistor having a first terminal coupled to the second terminal of the third transistor and a second terminal coupled to the ground terminal; and
a fourth resistor having a first terminal coupled to the second terminal of the fourth transistor and a second terminal coupled to the ground terminal.
15 . The integrated circuit of claim 14 , wherein the voltage reference circuit is a bandgap voltage reference circuit.
16 . The integrated circuit of claim 13 , wherein the first transistor has a same area as the fourth transistor, the second transistor has a same area as the third transistor, the first transistor has a difference area than the second transistor, and the third transistor has a difference area than the fourth transistor.
17 . The integrated circuit of claim 16 , further comprising a temperature generating component coupled to the first location and having an input coupled to an output of the voltage reference circuit.
18 . The integrated circuit of claim 14 , wherein the first, second, third and fourth transistors are NPN bipolar-junction transistors (BJTs).
19 . An integrated circuit comprising:
a first temperature sensor including:
a first bipolar-junction transistor (BJT) having first and second terminals and a control terminal, the first terminal coupled to the control terminal and a to a first current reference terminal;
a first resistor having a first terminal coupled to the second terminal of the first BJT and having a second terminal coupled to a ground terminal;
a second BJT having first and second terminals and a control terminal, the control terminal coupled to the control terminal of the first BJT; and
a second resistor having a first terminal coupled to the second terminal of the second BJT and having a second terminal coupled to the ground terminal;
a first current source having a first terminal coupled to the first terminal of the second BJT and a second terminal to a voltage reference terminal;
a second temperature sensor including:
a third BJT having first and second terminals and a control terminal, the first and control terminals coupled to a second current reference terminal;
a third resistor having a first terminal coupled to the second terminal of the third BJT and having a second terminal coupled to the ground terminal;
a fourth BJT having first and second terminals and a control terminal, the control terminal coupled to the control terminal of the third BJT; and
a fourth resistor having a first terminal coupled to the second terminal of the fourth BJT and having a second terminal coupled to the ground terminal; and
a second current source having a first terminal coupled to the first terminal of the fourth BJT and a second terminal to the voltage reference terminal.
20 . The integrated circuit of claim 19 , further comprising a temperature-independent voltage reference circuit having the voltage reference terminal and the first and second current reference terminals.
21 . The integrated circuit of claim 20 , further comprising:
the temperature-independent voltage reference circuit is a bandgap voltage reference circuit;
the first current source includes
a first field-effect transistor (FET) having first and second terminals and a control terminal, the second terminal and control terminal of the first FET coupled to the first terminal of the second BJT; and
a fifth resistor having a first terminal coupled to the first terminal of the first FET and a second terminal coupled to the voltage reference terminal; and
the second current source includes:
a second FET having first and second terminals and a control terminal, the second terminal of the second FET coupled to the first terminal of the fourth BJT, the control terminal of the second FET coupled to the control terminal of the first FET; and
a sixth resistor having a first terminal coupled to the first terminal of the second FET and a second terminal coupled to the voltage reference terminal.
22 . The integrated circuit of claim 21 , wherein the first through fourth BJT are NPN BJTs, and the first and second FETs are p-channel FETs.
23 . The integrated circuit of claim 19 wherein the first and fourth BJTs are proximal each other at a first location of the integrated circuit, the second and third BJTs are proximal each other at a second location of the integrated circuit, and the second location is distal the first location relative to a temperature gradient during operation of the integrated circuit.