Temperature drift compensation
A voltage reference circuit includes a bandgap circuit and a temperature compensation circuit. The temperature compensation circuit includes a first trim circuit, a second trim circuit, and a resistive digital-to-analog converter. The resistive digital-to-analog converter is coupled to the first trim circuit, the second trim circuit, and the bandgap circuit. The resistive digital-to-analog converter is configured to generate a temperature compensation voltage, and to provide the temperature compensation voltage to the bandgap circuit.
1. A method for trimming a voltage reference circuit, comprising:
adjusting an output voltage of a bandgap circuit to a reference voltage at a first temperature;
generating a temperature compensation voltage to adjust the output voltage as a function of temperature, the generating comprising setting a first resistive digital-to-analog converter to produce a weighted sum of a voltage proportional to absolute temperature and a voltage complementary to absolute temperature; and
providing the temperature compensation voltage to the bandgap circuit to adjust the output voltage.
2. The method of claim 1 , further comprising generating the voltage proportional to absolute temperature as the output voltage less three diode drop voltages.
3. The method of claim 1 , further comprising generating the voltage complementary to absolute temperature as two diode drop voltages.
4. The method of claim 1 , further comprising setting a second resistive digital-to-analog converter to scale the voltage proportional to absolute temperature to the reference voltage at the first temperature.
5. The method of claim 4 , further comprising opening a switch disposed between the first resistive digital-to-analog converter and a third resistive digital-to-analog converter while setting the second resistive digital-to-analog converter.
6. The method of claim 4 , further comprising setting a third resistive digital-to-analog converter to scale the voltage complementary to absolute temperature to the reference voltage at the first temperature.
7. The method of claim 6 , further comprising opening a switch disposed between the first resistive digital-to-analog converter and the second resistive digital-to-analog converter while setting the third resistive digital-to-analog converter.
8. The method of claim 1 , further comprising opening a switch to disconnect the first resistive digital-to-analog converter from the bandgap circuit while adjusting the output voltage of the bandgap circuit.