Voltage reference circuit with low-power bandgap

• US 7,808,387 B1
• Filed: 04/23/2008
• Issued: 10/05/2010
• Est. Priority Date: 06/07/2007
• Status: Active Grant

• Current Assignee: Impinj, Inc.
• Original Assignee: Impinj, Inc.
• Inventors: Kuhn, Jay A.
• Primary Examiner(s): TWEEL JR, JOHN ALEXANDER
• Application Number:
  US12/108,311
• Time in Patent Office: 895 Days
• Field of Search: 340/572.1, 340/572.5, 257/E21.112, 257/E27.112, 257/E29.273, 257/E29.3, 257/E43.003, 257/57, 257/255, 323/308, 365/185.05, 365/185.1, 365/185.18, 365/185.28, 438/163, 438/217, 438/289
• US Class Current: 340/572.1
• CPC Class Codes: G06K 19/0701 at least one of the integrated circuit chips comprising an arrangement for power management
• CPC Class Codes: G06K 19/0723 the record carrier comprising an arrangement for non-contact communication, e.g. wireless communication circuits on transponder cards, non-contact smart cards or RFIDs

Abstract

The present disclosure provides for a voltage reference circuit for Radio Frequency Identification (RFID) tag circuit. Such a circuit is formed in a substrate that is lightly doped with impurities of a first polarity. A first transistor having a first source connected to a ground, a first gate doped with impurities of the first polarity, and a first drain connected to the first gate at a reference node, a reference current source to provide a reference current to the reference node for generating a first reference voltage at the reference node, and an additional component for receiving the first reference voltage are disclosed.

Claims

1. A Radio Frequency Identification (RFID) tag circuit formed in a substrate that is lightly doped with impurities of a first polarity, comprising:

a first transistor having a first source connected to a ground, a first gate doped with impurities of the first polarity, and a first drain connected to the first gate at a reference node;

a reference current source to provide a reference current to the reference node for generating a first reference voltage at the reference node; and

an additional component for receiving the reference voltage.

2. The circuit of claim 1, in which

the reference current value is approximately 20 nA.

3. The circuit of claim 1, in which

the first transistor is formed in the substrate directly, without being in a well.

4. The circuit of claim 1, in which

a well is formed in the substrate, and

the first transistor is formed in the well.

5. The circuit of claim 1, in which

the first gate is doped with impurities of the first polarity only at a central region of the first gate, and the first gate is further doped with impurities of a second polarity opposite to the first polarity, at an edge region of the first gate surrounding the central region.

6. The circuit of claim 1, in which

the reference current source includes a second transistor.

7. The circuit of claim 6, in which

the first transistor has a channel region that is doped with impurities, and

the second transistor has a channel region doped with impurities of a polarity that is opposite to the polarity of the impurities of the channel region of the first transistor.

8. The circuit of claim 6, in which

the reference current source further includes

a third transistor coupled serially with the second transistor.

9. The circuit of claim 8, in which

the second transistor is made substantially identically as the third transistor.

10. The circuit of claim 1, in which

the additional component includes an output buffer to provide an output reference voltage responsive to receiving the first reference voltage.

11. The circuit of claim 10, in which

the output buffer includes a fourth transistor having a fourth gate to receive the first reference voltage, and a fourth source to provide the output reference voltage.

12. The circuit of claim 11, in which

an output current is provided by the fourth source, which is substantially equal to the reference current.

13. The circuit of claim 11, in which

an output current is provided by the fourth source, which is substantially greater than the reference current.

14. The circuit of claim 11, in which

the fourth source is coupled to the ground via a current sink.

15. The circuit of claim 14, in which

the current sink is configured to sink a current that is substantially equal to the reference current.

16. The circuit of claim 11, in which

the fourth source is coupled to the ground via a capacitor.

17. The circuit of claim 16, in which

the capacitor is configured from a transistor.

18. The circuit of claim 11, in which

the fourth gate is doped with impurities of a second polarity opposite to the first polarity.

19. The circuit of claim 11, in which

the fourth transistor is formed in the substrate directly, without being in a well.

20. The circuit of claim 11, in which

a well is formed in the substrate, and

the fourth transistor is formed in the well.

21. The circuit of claim 11, in which

a current density through the first transistor and a current density through the fourth transistor are substantially equal.

22. The circuit of claim 11, in which

the first gate is doped with impurities of the first polarity only at a central region of the first gate, the central region forming an electrically effective gate length of L1, and the first gate is further doped with impurities of a second polarity opposite to the first polarity, at an edge region of the first gate surrounding the central region,

the fourth gate has an electrically effective gate length of L2, and

the gate length of L1 and the gate length of L2 are substantially equal.

23. The circuit of claim 22, in which

the central region forms an electrically effective gate width W1,

the fourth gate has an electrically effective gate width of W2.

24. The circuit of claim 23, in which

the gate width of W1 and the gate width of W2 are substantially equal.

25. The circuit of claim 23, in which

the gate width of W2 is substantially greater than gate width of W1.

26. The circuit of claim 23, in which

the reference current source includes a second transistor and a third transistor coupled serially with the second transistor, the second transistor being made substantially identically as the third transistor.

27. The circuit of claim 1, in which

the additional component is an output buffer to provide an output reference voltage responsive to receiving the first reference voltage, the output buffer including a fourth transistor having a fourth gate to receive the first reference voltage, and a fourth source to provide the output reference voltage and an output current, the fourth source being coupled to the ground via a capacitor and a current sink,

the current sink is configured to sink a current that is substantially equal to the reference current;

and

a current density through the first transistor is substantially equal to a current density through the fourth transistor.

28. The circuit of claim 27, in which

the output current being substantially equal to the reference current.

29. The circuit of claim 27, in which

an output current being substantially greater than the reference current.

30. The circuit of claim 27, in which

the first gate is doped with impurities of the first polarity only at a central region of the first gate, the central region forming an electrically effective gate length of L1, and the first gate is further doped with impurities of a second polarity opposite to the first polarity, at an edge region of the first gate surrounding the central region,

the fourth gate has an electrically effective gate length of L2, and

the gate length of L1 and the gate length of L2 are substantially equal.

31. The circuit of claim 30, in which

the central region forms an electrically effective gate width W1, and

the fourth gate has an electrically effective gate width of W2.

32. The circuit of claim 31, in which

the gate width of W1 and the gate width of W2 are substantially equal.

33. The circuit of claim 31, in which

the gate width of W2 is substantially greater than gate width of W1.