Methods and apparatus for improving temperature drift of references

A method of temperature compensating the output of a reference circuit to better achieve the desired output of the reference circuit over temperature comprising the steps of:

• a) generating a first electrical parameter having a value which is substantially independent of temperature;
• b) generating a second electrical parameter having a value which has a substantially constant value above a first reference temperature and which has a value which varies with temperature in a predetermined manner at temperatures below the first reference temperature, the first and second electrical parameters being generated by an integrated circuit on the same integrated circuit substrate as at least part of the reference circuit;
• c) adjusting the output of the reference circuit when at the first reference temperature to obtain a desired output of the reference circuit at that temperature by applying a weighted portion of the first electrical parameter to the reference circuit;
• and
• d) adjusting the output of the reference circuit when at a second temperature substantially below the first reference temperature to obtain a desired output of the reference circuit at that temperature by applying a weighted portion of the second electrical parameter to the reference circuit.

A method of temperature compensating the output of a reference circuit to better achieve the desired output of the reference circuit over temperature comprising the steps of:

• a) generating a first electrical parameter having a value which is substantially independent of temperature;
• b) generating a second electrical parameter having a value which has a substantially constant value below a first reference temperature and which has a value which varies with temperature in a predetermined manner at temperatures above the first reference temperature;
• c) generating a third electrical parameter having a value which has a substantially constant value above a first reference temperature and which has a value which varies with temperature in a predetermined manner at temperatures below the first reference temperature, the first, second and third electrical parameters being generated by an integrated circuit on the same integrated circuit substrate as at least part of the reference circuit;
• d) adjusting the output of the reference circuit when at the first reference temperature to obtain a desired output of the reference circuit at that temperature by applying a weighted portion of the first electrical parameter to the reference circuit;
• e) adjusting the output of the reference circuit when at a second temperature substantially above the first reference temperature to obtain a desired output of the reference circuit at that temperature by applying a weighted portion of the second electrical parameter to the reference circuit;
• and
• f) adjusting the output of the reference circuit when at a third temperature substantially below the first reference temperature to obtain a desired output of the reference circuit at that temperature by applying a weighted portion of the third electrical parameter to the reference circuit.

A method of temperature compensating the output of a reference circuit realized at least in part in integrated circuit form to better achieve the desired output of the reference circuit over temperature comprising the steps of:

• providing temperature compensation circuitry:
• for generating a first electrical parameter having a value which is substantially independent of temperature;
• for generating a second electrical parameter having a value which has a substantially constant value below a first temperature and which has a value which varies with temperature in a predetermined manner at temperatures above the first temperature;
• for generating a third electrical parameter having a value which has a substantially constant value above a second temperature and which has a value which varies with temperature in a predetermined manner at temperatures below the second temperature;
• the compensation circuitry being on the same integrated circuit substrate as at least part of the reference circuit;
• adjusting at the time of wafer sort, the second and third electrical parameters so that the first and second temperatures defining the characteristics of the second and third electrical parameters are both a predetermined reference temperature;
• adjusting after packaging the integrated circuit:
• the output of the reference circuit when at the reference temperature to obtain a desired output of the reference circuit at that temperature by applying a weighted portion of the first electrical parameter to the reference circuit;
• adjusting the output of the reference circuit when at a third temperature substantially above the reference temperature to obtain a desired output of the reference circuit at that temperature by applying a weighted portion of the second electrical parameter to the reference circuit;
• and
• adjusting the output of the reference circuit when at a fourth temperature substantially below the reference temperature to obtain a desired output of the reference circuit at that temperature by applying a weighted portion of the third electrical parameter to the reference circuit.

A method of temperature compensating the output of a reference circuit realized at least in part in integrated circuit form to better achieve the desired output of the reference circuit over temperature comprising the steps of:

• providing temperature compensation circuitry:
• for generating a first electrical parameter having a value which is substantially independent of temperature;
• for generating a second electrical parameter having a value which has a substantially constant value below a first temperature and which has a value which varies with temperature in a first predetermined manner at temperatures above the first temperature;
• for generating a third electrical parameter having a value which has a substantially constant value above a second temperature and which has a value which varies with temperature in a second predetermined manner at temperatures below the second temperature;
• for generating a fourth electrical parameter having a value which has a substantially constant value below a third temperature and which has a value which varies with temperature in a third predetermined manner at temperatures above the third temperature;
• for generating a fifth electrical parameter having a value which has a substantially constant value above a fourth temperature and which has a value which varies with temperature in a fourth predetermined manner at temperatures below the fourth temperature;
• the compensation circuitry being on the same integrated circuit substrate as at least part of the reference circuit;
• adjusting at the time of wafer sort, the second, third, fourth and fifth electrical parameters so that the first, second, third and fourth temperatures defining the characteristics of the second, third, fourth and fifth electrical parameters are all a predetermined reference temperature, and applying a predetermined amount of the fourth and fifth electrical parameters to the output of the reference circuit;
• adjusting after packaging the integrated circuit:
• the output of the reference circuit when at the reference temperature to obtain a desired output of the reference circuit at that temperature by applying a weighted portion of the first electrical parameter to the reference circuit;
• adjusting the output of the reference circuit when at a third temperature substantially above the reference temperature to obtain a desired output of the reference circuit at that temperature by applying a weighted portion of the second electrical parameter to the reference circuit;
• and
• adjusting the output of the reference circuit when at a fourth temperature substantially below the reference temperature to obtain a desired output of the reference circuit at that temperature by applying a weighted portion of the third electrical parameter to the reference circuit.

A method of temperature compensating the output of a reference circuit realized at least in part in integrated circuit form to better achieve the desired output of the reference circuit over temperature comprising the steps of:

• providing temperature compensation circuitry:
• for generating a first electrical parameter having a value which is substantially independent of temperature;
• for generating a second electrical parameter having a value which has a substantially constant value below a first temperature and which has a value which varies with temperature in a first predetermined manner at temperatures above the first temperature;
• for generating a third electrical parameter having a value which has a substantially constant value above a second temperature and which has a value which varies with temperature in a second predetermined manner at temperatures below the second temperature;
• for generating a fourth electrical parameter having a value which has a substantially constant value below a third temperature and which has a value which varies with temperature in a third predetermined manner at temperatures above the third temperature;
• for generating a fifth electrical parameter having a value which has a substantially constant value above a fourth temperature and which has a value which varies with temperature in a fourth predetermined manner at temperatures below the fourth temperature;
• the compensation circuitry being on the same integrated circuit substrate as at least part of the reference circuit;
• adjusting at the time of wafer sort, the second, third, fourth and fifth electrical parameters so that the first, second, third and fourth temperatures defining the characteristics of the second, third, fourth and fifth electrical parameters are all a predetermined reference temperature;
• determining after packaging the integrated circuit, the compensation the reference circuit needs at the reference temperature, at two different temperatures above the reference temperature and at two different temperatures below the reference temperature;
• and
• applying weighted portions of the first, second, third, fourth and fifth electrical parameters to the reference circuit to obtain desired outputs of the reference circuit at all five temperatures.