Simplified curvature compensated bandgap using only ratioed components

Patent metadata

Field	Value
Publication number	US-11853096-B2
Application number	US-202217681021-A
Country	US
Kind code	B2
Filing date	Feb 25, 2022
Priority date	Oct 21, 2021
Publication date	Dec 26, 2023
Grant date	Dec 26, 2023

Abstract

A curvature compensated bandgap circuit that is capable of matching best-in-class two (2) parts-per-million performance without over-temperature trimming. This improves performance metrics for precision voltage reference products without requiring individual device tuning during production thereof. A core bandgap circuit comprises a main operational amplifier having a second order bowed voltage response over temperature. A ptat circuit is coupled to the core bandgap circuit to provide a sigmoidal third order shape for the bandgap voltage.

First claim

What is claimed is:

1. A precision bandgap reference circuit, comprising:
a core bandgap circuit producing a voltage having a bowed second order shape by a temperature; and
a proportional-to-absolute-temperature (ptat) circuit coupled to the core bandgap circuit, wherein the coupled core bandgap and ptat circuits produce a bandgap voltage having a varying sigmoidal shape by the temperature:

wherein the core bandgap circuit comprises:
a main operational amplifier having an output coupled to a base of a first NPN transistor, wherein the first NPN transistor has a collector coupled to a power supply positive and an emitter coupled to a bandgap voltage node;
diode configured second and third NPN transistors couple to positive and negative inputs, respectively, of the main operational amplifier and to second and third resistors, respectively, coupled to the bandgap voltage node, and the emitter of the third NPN transistor is couple to a power supply common and the emitter of the second NPN transistor is coupled to the ptat circuit; and
a first resistor, which first resistor is adjustable, coupled between the negative input of the main operational amplifier and the third NPN transistor.

2. The precision bandgap reference circuit according to claim 1 , wherein the ptat circuit comprises:
a compensation operational amplifier having an output coupled to an emitter of the second NPN transistor and a fourth resistor;
a diode configured fourth NPN transistor coupled between the fourth resistor and a negative input of the compensation operational amplifier;
a positive input of the compensation operational amplifier coupled to a fifth diode connected NPN transistor;
a fifth resistor coupled between the positive input of the compensation operational amplifier and the bandgap voltage node; and
a sixth resistor coupled between the output of the main operational amplifier and the negative input of the compensation operational amplifier.

3. The precision bandgap reference circuit of claim 1 , wherein the temperature is from about minus 40 degrees Celsius to about 120 degrees Celsius.

4. The precision bandgap reference circuit of claim 1 , wherein a selected resistance value of the first adjustable resistor is stored in a nonvolatile memory.

5. A precision bandgap reference circuit, comprising:
a core bandgap circuit having a positive temperature coefficient; and
proportional-to-absolute-temperature (ptat) circuit having a negative temperature coefficient coupled to the core bandgap circuit and is subtracted from the core bandgap circuit output voltage to produce a bandgap voltage;

wherein the bandgap circuit comprises:
a main operational amplifier having an output coupled to a base of a first NPN transistor, wherein the first NPN transistor has a collector coupled to a power supply positive and an emitter coupled to a bandgap voltage node;
second and third PNP transistor coupled to positive and negative inputs, respectively, of the main operational amplifier and to second and third resistors, respectively, coupled to the bandgap voltage node, and the collectors thereof coupled to a power supply common; and
a first adjustable resistor coupled between the negative input of the main operational amplifier and the emitter of the third PNP transistor.

6. The precision bandgap reference circuit according to claim 5 , wherein the ptat circuit comprises:
a compensation operational amplifier having an output coupled to bases of a fourth and the second PNP transistors;
a sixth diode configured PNP transistor coupled between a positive input of the compensation operational amplifier and the power supply common;
a fourth resistor coupled between a negative input of the compensation operational amplifier and an emitter of the fourth PNP transistor, wherein a collector of the fourth PNP transistor is coupled to the power supply common;
a fifth resistor coupled between the positive input of the compensation operational amplifier and the bandgap voltage node; and
a sixth resistor coupled between the output of the main operational amplifier and the negative input of the compensation operational amplifier.

7. The precision bandgap reference circuit of claim 5 , wherein the negative temperature coefficient ptat circuit generates a correlated output that is subtracted from the bandgap voltage to produce a sigmoidal voltage temperature curve that has minimal voltage variation over a temperature range.

8. The precision bandgap reference circuit of claim 7 , wherein the temperature range is from about minus 40 degrees centigrade to about 120 degrees Celsius.

9. The precision bandgap reference circuit of claim 6 , wherein the fourth resistor linearizes operation of the fourth PNP transistor.

10. The precision bandgap reference circuit of claim 5 , wherein a unit ratio for the second and third PNP transistors is N:M, respectively, where M is greater than N.

11. The precision bandgap reference circuit of claim 10 , where M is eight (8) and N is one (1).

12. The precision bandgap reference circuit of claim 5 , wherein the third PNP transistor comprises a parallel combination of M PNP transistors and has a greater current density than the second PNP transistor.

13. The precision bandgap reference circuit of claim 5 , wherein a resistance value of the first adjustable resistor is stored in a nonvolatile memory.

Assignees

• Microchip Tech Inc

Inventors

• Harris Michael
• Meacham Daniel

Classifications

• G05F3/225 Primary

  producing a current or voltage as a predetermined function of the temperature · CPC title

• G05F1/461

  using an operational amplifier as final control device · CPC title

• G05F3/30 Primary

  Regulators using the difference between the base-emitter voltages of two bipolar transistors operating at different current densities (G05F3/26 takes precedence) · CPC title