SUPPLY INVARIANT BANDGAP REFERENCE SYSTEM

• US 20120081099A1
• Filed: 09/30/2010
• Published: 04/05/2012
• Est. Priority Date: 09/30/2010
• Status: Active Grant

• Current Assignee: Cirrus Logic Incorporated
• Original Assignee: Cirrus Logic Incorporated
• Inventors: Melanson, John L., Drakshapalli, Prashanth, Harris, Larry L.
• Granted Patent: US 8,536,854 B2
• Time in Patent Office: Days
• US Class Current: 323/313
• CPC Class Codes: G05F 3/30 Regulators using the difference between the base-emitter voltages of two bipolar transistors operating at different current densities G05F3/26 takes precedence

Abstract

An electronic reference-signal generation system includes a supply invariant bandgap reference system that generates one or more bandgap reference signals that are substantially unaffected by bulk error currents. In at least one embodiment, the bandgap reference generates a substantially invariant bandgap reference signals for a range of direct current (DC) supply voltages. Additionally, in at least one embodiment, the bandgap reference system provides substantially invariant bandgap reference signals when the supply voltage varies due to alternating current (AC) voltages. In at least one embodiment, the bandgap reference system generates a bandgap reference voltage VBG, a “proportional to absolute temperature” (PTAT) current (“i_PTAT”) and a “zero dependency on absolute temperature” (ZTAT) current (“i_ZTAT”) that are substantially unaffected by variations in the supply voltage and unaffected by a bulk error current.

Claims

1. An apparatus comprising:

a bandgap reference circuit to generate one or more bandgap reference signals that are substantially invariant to at least changes in direct current values of a supply voltage of the bandgap reference circuit;

a current mirror, coupled to the bandgap reference circuit, to receive and mirror a control signal, wherein the control signal controls the one or more bandgap reference signals generated by the bandgap reference circuit; and

a proportional to absolute temperature reference signal generator coupled between the bandgap reference circuit and the current mirror to generate one or more proportional to absolute temperature currents from at least one of the bandgap reference signals, wherein the one or more proportional to absolute temperature currents are substantially invariant to at least changes in direct current values of the supply voltage of the bandgap reference circuit.

2. The apparatus of claim 1 wherein the current mirror comprises an n-channel transistors to generate a mirror of the control signal, and the proportional to absolute temperature reference signal generator comprises p-channel transistors to generate one or more proportional to absolute temperature currents.

3. The apparatus of claim 1 wherein each proportional to absolute temperature current is substantially invariant to bulk error currents in the current mirror.

4. The apparatus of claim 1 wherein the bandgap reference signals are substantially invariant to transients of the supply voltage.

5. The apparatus of claim 1 wherein the bandgap reference signals include a reference voltage that is substantially invariant to at least changes in direct current values of a supply voltage of the bandgap reference circuit.

6. The apparatus of claim 1 further comprising:

an operational amplifier coupled between the bandgap reference circuit and the current mirror, wherein, during operation of the apparatus, the operational amplifier responds to changes in voltages in the bandgap reference circuit and drives a current in the current mirror to maintain the supply invariant bandgap reference voltage.

7. The apparatus of claim 6 wherein the operational amplifier includes a low frequency dominant path and a high frequency dominant path to respectively respond to alternating current and direct current changes in the voltages of the bandgap reference circuit.

8. The apparatus of claim 6 wherein the current mirror includes a source-follower field effect transistor having a gate coupled to the operational amplifier, a drain coupled to the bandgap reference circuit, and a source coupled to a reference voltage, wherein the operational amplifier drives a gate voltage of the field effect transistor to compensate for at least the bulk error currents.

9. The apparatus of claim 1 wherein one of the bandgap reference signals is a proportional to absolute temperature current and the proportional to absolute temperature reference signal generator generates copies of the proportional to absolute temperature current generated by the bandgap reference circuit.

10. The apparatus of claim 1 wherein the apparatus is further configured to generate a zero dependency on absolute temperature current that is invariant to at least changes in direct current values of a supply voltage of the bandgap reference circuit.

11. The apparatus of claim 10 further comprising:

a zero dependency on absolute temperature to generate at least one copy of the zero dependency on absolute temperature current, wherein the copy of the zero dependency on absolute temperature current is invariant to at least changes in direct current values of a supply voltage of the bandgap reference circuit.

12. The apparatus of claim 1 wherein the bandgap reference circuit is referenced to the supply voltage.

13. A method comprising:

generating one or more bandgap reference signals that are substantially invariant to at least changes in direct current values of a supply voltage of the bandgap reference circuit;

receiving a control signal;

mirroring the control signal using a current mirror to control the one or more bandgap reference signals generated by the bandgap reference circuit; and

generating one or more proportional to absolute temperature currents from at least one of the bandgap reference signals, wherein the one or more proportional to absolute temperature currents are substantially invariant to at least changes in direct current values of the supply voltage of the bandgap reference circuit.

14. The method of claim 13 wherein generating one or more proportional to absolute temperature currents further comprises:

generating one or more proportional to absolute temperature currents to be substantially invariant to bulk error currents in the current mirror.

15. The method of claim 13 wherein generating the one or more bandgap reference signals further comprises generating one or more bandgap reference signals to be substantially invariant to transients of the supply voltage.

16. The method of claim 13 wherein generating the one or more bandgap reference signals further comprises generating one or more bandgap reference signals to be substantially invariant to at least changes in direct current values of a supply voltage of the bandgap reference circuit.

17. The method of claim 13 further comprising:

generating a control signal to respond to changes in voltages in the bandgap reference circuit and drive a current in the current mirror to maintain substantial invariance of the one or more bandgap reference signals to at least changes in direct current values of a supply voltage of the bandgap reference circuit.

18. The method of claim 17 wherein generating a control signal to respond to changes in voltages in the bandgap reference circuit further comprises:

generating the control signal using a high frequency dominant path to respond to alternating current voltage changes in the voltages of the bandgap reference circuit; and

generating the control signal using a low frequency dominant path to respond to direct current voltage changes in the voltages of the bandgap reference circuit.

19. The method of claim 17 wherein the current mirror includes a source-follower field effect transistor having a gate coupled to the operational amplifier, a drain coupled to the bandgap reference circuit, and a source coupled to a reference voltage, wherein the operational amplifier drives a gate voltage of the field effect transistor to compensate for at least the bulk error currents.

20. The method of claim 13 wherein one of the bandgap reference signals is a proportional to absolute temperature current and generating one or more proportional to absolute temperature currents from at least one of the bandgap reference signals further comprises generating copies of the proportional to absolute temperature current generated by the bandgap reference circuit.

21. The method of claim 13 further comprising:

generating a zero dependency on absolute temperature current that is substantially invariant to at least changes in direct current values of the supply voltage of the bandgap reference circuit.

22. The method of claim 21 further comprising:

generating a zero dependency on absolute temperature current that is substantially invariant to at least changes in direct current values of the supply voltage of the bandgap reference circuit and bulk error currents.

23. The method of claim 13 further comprising:

referencing the bandgap reference circuit to the supply voltage.

24. A system comprising:

a bandgap reference circuit to generate one or more bandgap reference signals that are substantially invariant to at least changes in direct current values of a supply voltage of the bandgap reference circuit, wherein the bandgap reference circuit includes first and second parallel current paths, each current path includes one or more diodes, and the total diode forward voltage reduction during operation of the bandgap reference circuit is different for the two paths;

an operational amplifier having an inverting node coupled to the first parallel current path of the bandgap reference circuit and a non-inverting node coupled to the second parallel current path of the bandgap reference circuit, wherein the operational amplifier is configured to generate a control signal to maintain equal currents through the first and second parallel current paths of the bandgap reference circuit;

a current mirror, coupled to the bandgap reference circuit, to receive and mirror the control signal; and

a proportional to absolute temperature reference signal generator coupled between the bandgap reference circuit and the current mirror to generate one or more proportional to absolute temperature currents from at least one of the bandgap reference signals, wherein the one or more proportional to absolute temperature currents are substantially invariant to at least changes in direct current values of the supply voltage of the bandgap reference circuit.

25. The apparatus of claim 24 wherein the apparatus is further configured to generate a zero dependency on absolute temperature current that is invariant to at least changes in direct current values of a supply voltage of the bandgap reference circuit.