Reference voltage generation using compensation current method

• US 7,279,960 B1
• Filed: 08/30/2005
• Issued: 10/09/2007
• Est. Priority Date: 08/30/2005
• Status: Active Grant

• Current Assignee: National Semiconductor Corporation (Texas Instruments, Inc.)
• Original Assignee: National Semiconductor Corporation (Texas Instruments, Inc.)
• Inventors: Lee, Bumha
• Primary Examiner(s): Lam; Tuan T.
• Assistant Examiner(s): Hernandez; William
• Application Number:
  US11/215,174
• Time in Patent Office: 770 Days
• Field of Search: None
• US Class Current: 327/538
• CPC Class Codes: G05F 3/242 with compensation for device parameters, e.g. channel width modulation, threshold voltage, processing, or external variations, e.g. temperature, loading, supply voltage

Abstract

A reference voltage generator that may be useful in analog-to-digital converter (ADC) circuits includes compensation for errors such as from non-ideal considerations such as semiconductor processing variations, mismatch errors, temperature gradients, and parasitic effects. The compensation method employs a correction current that is provided to the reference voltage generator to adjust the delay time and stability of the resulting reference voltage or voltages.

Claims

1. An apparatus for generating a stable voltage reference from a reference voltage (V_REF), the apparatus comprising:

a parasitic resistance that is coupled between a first node and a second node;

a first resistance circuit that is coupled between the second node and a third node, wherein the third node is associated with a signal ground;

a voltage reference circuit that is arranged to provide a first input reference voltage (V_REFP) to the first node and a second input reference voltage (V_REFN) to the third node such that the difference between the first input reference voltage (V_REFP) and the second input reference voltage (V_REFN) is responsive to the reference voltage (V_REF);

a control circuit that is arranged to provide a first control signal (CTL_P) such that;

the first control signal (CTL_P) is responsive to changes from the reference voltage (V_REF), wherein the control circuit includes a second resistance circuit that is arranged such that a voltage across the second resistance circuit is substantially equal to the reference voltage (V_REF), and arranged such that the first control signal (CTL_P) is responsive to changes in operational characteristics of the second resistance circuit and changes in the reference voltage (V_REF; and

a first controlled current source (I<sub>COM—

P</sub>) that is coupled between a power supply terminal and the second node, wherein the first controlled current source (I<sub>COMP—

P</sub>) is responsive to the first control signal (CTL_P) such that the voltage drop across the first resistance circuit is maintained, wherein the effect of the parasitic resistance is mitigated by operating the first controlled current source (I<sub>COMP—

P</sub>) in an open loop configuration with respect to the first input reference voltage (V_REFP).

2. The apparatus of claim 1, wherein the parasitic resistance comprises at least one member of a group comprising:

a metal trace in a circuit board, a metal trace in an integrated circuit, a poly-silicon trace in an integrated circuit, a conductor that is in electrical communication between the first node and the second node, a conductive bonding pad, a wire bond, and a package lead-frame.

3. The apparatus of claim 1, the first resistance circuit comprising at least one member of a group comprising:

a first resistor that is series coupled to a second resistor between the second node and the third node, and an array of resistors that are series coupled between the second node and the third node.

4. The apparatus of claim 1, wherein the voltage reference circuit includes at least one member of a group comprising:

a band-gap reference, a regulated voltage reference, a high-speed voltage reference, and a filter capacitor.

5. The apparatus of claim 1, wherein the control circuit is arranged to replicate the operational characteristics of the first resistance circuit with the second resistance circuit.

6. The apparatus of claim 1, wherein:

the first resistance circuit comprises a first array of resistors that are arranged in series with one another, the second resistance circuit in the control circuit comprises a second array of resistors that are arranged in series with one another, and the first array of resistors has matched operational characteristics with the second array of resistors.

7. The apparatus of claim 6, wherein each resistor of the first array of resistors and the second array of resistors are matched to one another and arranged in a common area of an integrated circuit such that the matched operational characteristics are provided.

8. The apparatus of claim 6, wherein each resistor of the first array of resistors is ratio matched to each resistor of the second array of resistors such that the matched operational characteristics are provided.

9. The apparatus of claim 1, further comprising:

a second parasitic resistance that is coupled between a fourth node and the third node; and

a second controlled current source (I<sub>COMP—

N</sub>) that is coupled between the third node and the signal ground such that the third node is coupled to the circuit ground through the second controlled current source (I<sub>COMP—

N</sub>), wherein the second controlled current source (I<sub>COMP—

N</sub>) is responsive to a second control signal (CTL_N) such that the voltage drop across the first resistance circuit is maintained, wherein the voltage reference circuit is arranged to provide the second input reference voltage (V_REFN) to the third node through the second parasitic resistance via the fourth node, and wherein the control circuit is arranged to provide the second control signal (CTL_N) such that the second control signal (CTL_N) is responsive to changes from the reference voltage (V_REF).

10. The apparatus of claim 9, wherein the voltage reference circuit is arranged to provide the first input reference voltage (V_REFP) and the second input reference voltage (V_REFN) as a controlled voltage drop across the second node and the third node, and wherein the control circuit is arranged to control the first controlled current source (I_COMP—

_P) and the second controlled current source (I<sub>COMP—

N</sub>) such that the voltage drop is maintained.

11. An apparatus for generating a stable voltage reference from a reference voltage (V_REF), the apparatus comprising:

a voltage reference circuit that is arranged to provide a first note reference voltage (V_REFP) a first node and a second input reference voltage (V_REFN) to a second node in response to the reference voltage (V_REF);

a first parasitic resistance that is coupled between the first node and a third node;

a second parasitic resistance that is coupled between the second node and a fourth node;

a first resistor array circuit that is coupled between the third node and the fourth node;

a second resistor array circuit that is coupled between a fifth node and a sixth node, wherein the first resistor array circuit is matched in operational performance with the second resistor array circuit;

a first amplifier circuit that is arranged to adjust an internal control signal in response to a comparison between an internal reference voltage (V_REFX) and the reference voltage (V_REF);

a first transistor circuit that is arranged to control a current flow through the second resistor array circuit in response to the internal control signal such that the internal reference signal is generated as a voltage across the second resistor array;

a second transistor circuit that is arranged to provide a first control signal and a second control signal in response to the current flow through the second resistor array circuit;

a first controlled current source (I<sub>COMP—

P</sub>) that is arranged to provide a first current to the third node in response to the first control signal (CTL_P); and

a second controlled current source (I<sub>COMP—

N</sub>) that is arranged to provide a second current to the fourth node in response to the second control signal (CTL_N), wherein the first and second controlled current sources (I<sub>COM—

P</sub>, I<sub>COMP—

N</sub>) are arranged in cooperation with the voltage reference circuit and the first resistor array circuit to maintain a substantially constant voltage drop across the first resistor array circuit.

12. The apparatus of claim 11, the voltage reference circuit comprising:

a differential amplifier circuit that includes;

a first output that is coupled to the first node, a second output that is coupled to the second node, a first input that is coupled to a seventh node, and a second input that is coupled to an eighth node;

a first resistor circuit that is coupled between the first node and the seventh node;

a second resistor circuit that is coupled between the second node and the eighth node;

a third resistor circuit that is coupled between the seventh node and the input reference signal; and

a fourth resistor circuit that is coupled between the eighth node and a power supply terminal.

13. The apparatus of claim 11, wherein the first resistor array circuit comprises a plurality of unit-sized resistors that are arranged in series with one another;

wherein the junction between each of the unit sized resistors corresponds to a different reference voltage level.

14. The apparatus of claim 11, wherein the first resistor array circuit and the second resistor array circuit are each arranged as a plurality of unit-sized resistors that are arranged in series with one another, such that the first resistor array circuit is matched to the second resistor array circuit.

15. The apparatus of claim 11, wherein the first transistor circuit includes a field effect transistor that is responsive to the internal control signal.

16. The apparatus of claim 11, wherein the first transistor circuit comprises a first transistor, and the second transistor circuit comprises a second transistor, wherein:

the first transistor is responsive to the internal control signal to adjust the current flow through the second resistor array circuit, the second transistor is configured as a diode circuit that is arranged to provide a sense voltage in response to the current flow through the second resistor array circuit.

17. The apparatus of claim 16, the second transistor circuit further comprising a current mirror circuit that is responsive to the sense voltage, and arranged to provide either the first control signal or the second control signals.

18. The apparatus of claim 16, the second transistor circuit further comprising a first current mirror circuit that is responsive to the sense voltage and arranged to provide the first control signal;

and a second current mirror circuit that is responsive to the sense voltage and arranged to provide the second control signal.

19. An apparatus for generating a stable voltage reference from a reference voltage (V_REF), the apparatus comprising:

a means for generating a first difference voltage between a first node and a second node in response to the reference voltage (V_REF);

a means for coupling the first node to a third node;

a means for coupling the second node to a fourth node;

a first resistor means that is coupled between the third node and the fourth node;

a first controlled current means that is arranged to provide a first controlled current to the third node in response to a first control signal;

a second controlled current means that is arranged to provide a second controlled current to the fourth node in response to a second control signal;

a second resistor means that is coupled between a fifth node and a sixth node, wherein the operational characteristics of the second resistor means is matched to the first resistor means;

a first control means that is arranged to;

maintain second difference voltage between the fifth node and the sixth node in response to the reference voltage (V_REF); and

a current sense means that is arranged to sense a current flow in the second resistor means and generate the first control signal and the second control signal.

20. A method for generating a plurality of stable reference voltages from a reference voltage (V_REF), the method comprising:

generating a first difference voltage between a first node and a second node in response to the reference voltage (V_REF);

coupling the first node to a third node;

coupling the second node to a fourth node;

coupling a first current to the third node in response to a first control signal;

coupling a second current to the fourth node in response to a second control signal;

setting the plurality of stable reference voltages with a first resistor array that is coupled between the third node and the fourth node;

controlling a second difference voltage across a second resistor array such that the second difference voltage is substantially the same as the first difference voltage;

sensing a current flow in the second resistor array;

adjusting the first and second control signals in response to the sensed current flow; and

adjusting the plurality of stable reference voltages in response to the first and second control signals.