Method and circuit for trimming a current source in a package

• US 7,138,868 B2
• Filed: 08/11/2004
• Issued: 11/21/2006
• Est. Priority Date: 08/11/2004
• Status: Active Grant

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Hiser, Daryl, Sanchez, Stephen J.
• Primary Examiner(s): Choe, Henry
• Application Number:
  US10/917,189
• Publication Number:
  US 20060033572A1
• Time in Patent Office: 832 Days
• Field of Search: 327/541, 327/543, 330/256, 330/252, 330/269
• US Class Current: 330/256
• CPC Class Codes: H03F 2203/45366 the AAC comprising multiple transistors parallel coupled at their gates only, e.g. in a cascode dif amp, only those forming the composite common source transistor
• CPC Class Codes: H03F 3/45183 Long tailed pairs H03F3/4521, H03F3/45237 take precedence
• CPC Class Codes: H03F 3/45475 using IC blocks as the active amplifying circuit

Abstract

A method and circuit for trimming a current source packaged with a device can facilitate trimming of the current source without the need for additional pins or dual function pins, resulting in improved accuracy and/or simplified trimming techniques. An exemplary packaged device is configured with a trimming circuit comprising a current trimming network and a coupling circuit. An exemplary packaged device can comprise any op amp, current or voltage reference, and/or sensor device, and is configured with one or more monitor inputs. An exemplary current trimming network comprises a variable current source and a reference current source, wherein a magnitude of the variable current source can be compared to the magnitude of the reference current source. An exemplary coupling circuit is coupled between the current trimming network and the device and is configured for enabling and disabling connection of an output of the current trimming network and a monitor input of the device. During an exemplary trimming method, the variable current source is configured with a magnitude adjusted to a desired proportion of a magnitude of the reference current source, with the current trimming network configured to produce a current proportional to the difference, sum, or product of the first and second current sources.

Claims

1. A packaged circuit configured for trimming a current source within said packaged circuit, said packaged circuit comprising:

a device having a monitor input and a measurable device parameter;

a current trimming network comprising a variable current source, a reference constant current source and an output; and

a coupling circuit configured for connecting said output of said trimming network to said monitor input of said device to facilitate adjustment of said variable current source;

wherein said current trimming network is configured to enable a magnitude of said variable current source to be compared to a magnitude at said reference constant current source.

2. The packaged circuit of claim 1, wherein said device comprises one of an op amp, reference and a sensor device.

3. The packaged circuit of claim 1, wherein said device parameter comprises one of an output voltage, input voltage offset, bandwidth and slew rate of said device.

4. The packaged circuit of claim 1, wherein said current trimming network is configured to adjust said magnitude of said variable current source to a desired proportion of said magnitude of said reference constant current source.

5. The packaged circuit of claim 1, wherein said current trimming network is configured to adjust said magnitude of said variable current source until a desired value of said device parameter is achieved.

6. The packaged circuit of claim 1, wherein said current trimming network is configured to provide an output current proportional to a difference in magnitudes of said variable current source and said reference constant current source.

7. The packaged circuit of claim 6, wherein said output current proportional to said difference in magnitudes is coupled to said monitor input of said device to facilitate measurement of said device parameter.

8. The packaged circuit of claim 6, wherein said variable current source and said reference constant current source are connected in series with an output junction in between.

9. The packaged circuit of claim 1, wherein said current trimming network is configured to provide an output current proportional to at least one of a sum and a product of said magnitudes of said variable current source and said reference constant current source.

10. The packaged circuit of claim 9, wherein said current trimming network is configured to provide said proportional output current at a first output, and to provide a replica current of said reference constant current source at a second output.

11. The packaged circuit of claim 1, wherein said current trimming network is configured to provide a variable current from said variable current at a first output, and to provide a reference constant current from said reference constant current source at a second output.

12. The packaged circuit of claim 1, wherein said coupling circuit is configured for disabling a connection between said current trimming network and said device to obtain a first measurement condition for measurement of said device parameter.

13. The packaged circuit of claim 12, wherein said coupling circuit is configured for enabling a connection between said current trimming network and said device to obtain a second measurement condition for a second measurement of said device parameter.

14. The packaged circuit of claim 13, wherein said coupling circuit is configured for sourcing current from and sinking current to said monitor input.

15. A trimming circuit configured for trimming a current source packaged with a device, said trimming circuit comprising:

a current trimming network comprising a variable current source, a reference constant current source and an output; and

a coupling circuit configured for connecting said output of said trimming network to a monitor input of the device to facilitate adjustment of said variable current source;

wherein said current trimming network is configured to enable a magnitude of said variable current source to be compared to a magnitude of said reference constant current source.

16. The trimming circuit of claim 15, wherein said current trimming network is configured to adjust said magnitude of said variable current source to a desired proportion of said magnitude of same reference constant current source.

17. The trimming circuit of claim 15, wherein said current trimming network is configured to adjust said magnitude of said variable current source until a desired value of a device parameter for the device is achieved.

18. The trimming circuit of claim 15, wherein said current trimming network is configured to provide an output current proportional to a difference in magnitudes of said variable current source and said reference constant current source.

19. The trimming circuit of claim 18, wherein said output current proportional to said difference in magnitudes is coupled to the monitor input of the device to facilitate measurement of a device parameter.

20. The trimming circuit of claim 18, wherein said variable current source and said reference constant current source are connected in series with an output junction in between.

21. The trimming circuit of claim 15, wherein said current trimming network is configured to provide an output current proportional to at least one of a sum and a product of said magnitudes of said variable current source and said reference constant current source.

22. The trimming circuit of claim 21, wherein said current trimming network is configured to provide said proportional output current at a first output, and to provide a replica current of said reference constant current source at a second output.

23. The trimming circuit of claim 15, wherein said current trimming network is configured to provide a variable current from said variable current at a first output, and to provide a reference constant current from said reference constant current source at a second output.

24. The trimming circuit of claim 15, wherein said coupling circuit is configured for disabling a connection between said current trimming network and the device to obtain a first measurement condition for measurement of a device parameter.

25. The trimming circuit of claim 24, wherein said coupling circuit is configured for enabling a connection between said current trimming network and the device to obtain a second measurement condition for a second measurement of the device parameter.

26. A method for trimming a current source in a packaged device, said method comprising:

establishing a first measurement condition by disabling a connection between a current trimming network and said packaged device and recording a first measurement of a device parameter;

establishing a second measurement condition by enabling a connection between an output of said current trimming network and a monitor input of said packaged device and recording a second measurement of a device parameter;

comparing said first measurement of a device parameter with said second measurement of a device parameter; and

iteratively adjusting a variable current source within said current trimming network until a desired value of said device parameter is achieved.

27. The trimming method of claim 26, wherein said establishing a second measurement condition comprises enabling a connection between a second output of said current trimming network comprising a replica of a reference current and a second monitor input of said packaged device.

28. The trimming method of claim 27, wherein prior to iteratively adjusting a variable current source, said method further comprises recording a first difference value comprising a difference between said first measurement of a device parameter with said second measurement of a device parameter.

29. The trimming method of claim 28, wherein prior to iteratively adjusting a variable current source, said method further comprises establishing a third measurement condition by enabling a connection between a first output of said current trimming network, said first output comprising at least one of a sum of a variable current and a reference current, a product of said variable current and said reference current, and a variable current, and a second monitor input of said packaged device and recording a third measurement of a device parameter.

30. The trimming method of claim 29, wherein prior to iteratively adjusting a variable current source, said method further comprises recording a second difference value comprising a difference between said first measurement of a device parameter with said third measurement of a device parameter.

31. The trimming method of claim 30, wherein said iteratively adjusting a variable current source within said current trimming network comprises re-measuring said device parameter while in said third measurement condition, recalculating said second difference value, and adjusting said variable current source until said second difference value converges to a desired proportion of said first difference value.