Current source with variable resistor circuit

Patent metadata

Field	Value
Publication number	US-10345841-B1
Application number	US-201816006247-A
Country	US
Kind code	B1
Filing date	Jun 12, 2018
Priority date	Jun 12, 2018
Publication date	Jul 9, 2019
Grant date	Jul 9, 2019

Abstract

A current source circuit includes a first variable resistor circuit. The first variable resistor circuit includes a resistive material and a first plurality of tap inputs configured to set a resistance of the first variable resistor circuit. The current source circuit includes an output configured to provide a current. The current is adjustable by varying the resistance of the first variable resistor circuit. The current source circuit includes a second variable resistor circuit. The second variable resistor circuit includes a resistive material of a same resistive material type as the resistive material of the first variable resistor circuit. The second variable resistor circuit includes a second plurality of tap inputs configured to set a resistance of the second variable resistor circuit. Each tap resistance of the second variable resistor circuit is proportional to a corresponding tap resistance of the first variable resistor circuit. A first terminal of the second variable resistor circuit is coupled to a first test port and a second terminal of the second variable resistor circuit is coupled to a second test port to allow for a resistance measurement of the second variable resistor circuit during a test mode. The current source circuit includes a non-volatile storage circuit configured to store a tap value generated during the test mode corresponding to a set of select signal values for the second plurality of tap inputs which provides a desired resistance of the second variable resistor circuit as determined during the test mode and to provide a set of select signal values for the first plurality of tap inputs based on the tap value stored in the non-volatile storage circuit.

First claim

What is claimed is:

1. A current source circuit comprising:
a first variable resistor circuit, wherein the first variable resistor circuit includes a resistive material and a first plurality of tap inputs configured to set a resistance of the first variable resistor circuit;
an output configured to provide a current, wherein the current is adjustable by varying the resistance of the first variable resistor circuit;
a second variable resistor circuit, wherein:
the second variable resistor circuit includes a resistive material of a same resistive material type as the resistive material of the first variable resistor circuit,
the second variable resistor circuit includes a second plurality of tap inputs configured to set a resistance of the second variable resistor circuit, wherein each tap resistance of the second variable resistor circuit is proportional to a corresponding tap resistance of the first variable resistor circuit, and
a first terminal of the second variable resistor circuit is coupled to a first test port and a second terminal of the second variable resistor circuit is coupled to a second test port to allow for a resistance measurement of the second variable resistor circuit during a test mode; and

a non-volatile storage circuit configured to store a tap value generated during the test mode corresponding to a set of select signal values for the second plurality of tap inputs which provides a desired resistance of the second variable resistor circuit as determined during the test mode and to provide a set of select signal values for the first plurality of tap inputs based on the tap value stored in the non-volatile storage circuit.

2. The current source circuit of claim 1 , wherein each tap resistance of the second variable resistor circuit has a same tap resistance as each corresponding tap resistance of the first variable resistor circuit.

3. The current source circuit of claim 1 , further comprising:
a current mirror, wherein a leg of the current mirror comprises the first variable resistor circuit.

4. The current source circuit of claim 1 , wherein the set of select signal values for the first plurality of tap inputs based on the tap value stored in the non-volatile storage circuit is provided to the first variable resistor circuit during normal operation.

5. The current source circuit of claim 4 , wherein, during normal operation, the current source circuit provides current though the first variable resistor circuit and does not provide current through the second variable resistor circuit.

6. The current source circuit of claim 1 , wherein the current source circuit is characterized as a transconductance current source.

7. The current source circuit of claim 1 , wherein each tap input of the first plurality of tap inputs enables a corresponding tap node along a resistor stack of the first variable resistor circuit to be shorted to a supply voltage terminal.

8. The current source circuit of claim 7 , and each tap input of the second plurality of tap inputs enables a corresponding tap node along a resistor stack of the second variable resistor circuit to be shorted to a test port.

9. The current source circuit of claim 1 , wherein the resistive material each of the first variable resistor circuit and second variable resistor circuit has a same layout structure.

10. The current source circuit of claim 1 , wherein the current source circuit is formed in an integrated circuit and wherein the resistive material of the first variable resistor circuit and the second variable resistor circuit are formed in a same layer of the integrated circuit.

11. The current source circuit of claim 1 , wherein the resistive material type of each of the first and second variable resistor circuits is characterized as polysilicon.

12. A successive approximation register analog to digital converter circuit comprising:
a latching comparator;
a comparator stage having an output coupled to the latching comparator; and
the current source circuit of claim 1 coupled to provide the current to the comparator stage.

13. A method of operating a current source circuit, the current source circuit includes a first variable resistor circuit and an output configured to provide a current which is adjustable by varying a resistance of the first variable resistor circuit, the method comprising:
during a test mode, adjusting tap inputs of a second variable resistor circuit to vary a resistance of the second variable resistor circuit until a desired resistance of the second variable resistor circuit is achieved and storing a resulting tap value corresponding to the tap inputs which resulted in the desired resistance of the second variable resistor circuit; and
during normal operation, setting tap inputs of the first variable resistor circuit based on the stored resulting tap value, wherein the current source circuit provides current through the first variable resistor circuit to an output, wherein the second variable resistor circuit includes a resistive material of a same resistive material type as a resistive material of the first variable resistor circuit;
wherein during normal operation, current is not provided through the second variable resistor circuit.

14. The method of claim 13 , wherein each tap resistance of the second variable resistor circuit is proportional to a corresponding tap resistance of the first variable resistor circuit.

15. The method of claim 13 , wherein each tap resistance of the second variable resistor circuit is equal to as a corresponding tap resistance of the first variable resistor circuit.

16. The method of claim 13 , further comprising:
during the test mode, coupling a tester to each end of the second variable resistor circuit, wherein the adjusting is performed by the tester.

17. The method of claim 13 , wherein the resulting tap value is stored in a non-volatile storage circuit.

18. A current source circuit comprising:
a variable resistor circuit, wherein the variable resistor circuit includes a resistive material and a first plurality of tap inputs configured to set a resistance of the variable resistor circuit;
an output configured to provide a current, wherein the current is adjustable by varying the resistance of the variable resistor circuit;
a replica variable resistor circuit, wherein:
the replica variable resistor circuit includes a resistive material of a same resistive material type as the resistive material of the variable resistor circuit,
the replica variable resistor circuit includes a second plurality of tap inputs configured to set a resistance of the replica variable resistor circuit, wherein each tap resistance of the replica variable resistor circuit is a same tap resistance as a corresponding tap resistance of the variable resistor circuit, and
the replica variable resistor circuit is coupled to a test port such that, during a test mode, a tester is capable of determining a desired resistance of the replica variable resistor circuit, wherein a set of select signal values for the second plurality of tap inputs corresponds to the desired resistance; and

a non-volatile storage circuit configured to store a tap value generated during the test mode corresponding to the set of select signal values for the second plurality of tap inputs, wherein during a normal operational mode, the first plurality of tap inputs receives a set of select signal values that are based on the tap value stored in the non-volatile storage circuit in order to set the resistance of the variable resistor circuit to a same resistance as the des

Assignees

• Nxp Usa Inc

Inventors

• Jones Iii Robert S
• Jin Xiankun

Classifications

• G05F3/26

  Current mirrors · CPC title

• H03M1/38

  sequentially only, e.g. successive approximation type (converting more than one bit per step H03M1/14) · CPC title

• G01R31/2884

  using dedicated test connectors, test elements or test circuits on the IC under test (G01R31/2855 takes precedence) · CPC title

• G05F1/63 Primary

  using variable impedances in series with the load as final control devices · CPC title

• G05F3/242 Primary

  with compensation for device parameters, e.g. channel width modulation, threshold voltage, processing, or external variations, e.g. temperature, loading, supply voltage · CPC title