R-2R resistor ladder trim circuits

Patent metadata

Field	Value
Publication number	US-11356114-B2
Application number	US-202117192397-A
Country	US
Kind code	B2
Filing date	Mar 4, 2021
Priority date	Mar 4, 2020
Publication date	Jun 7, 2022
Grant date	Jun 7, 2022

Abstract

In some examples, a system includes an integrated circuit comprising a transistor, a first amplifier coupled to the transistor, a second amplifier having an output and coupled to the transistor and the first amplifier, and an R-2R resistor ladder having multiple rungs. Each rung is switchably coupled to a terminal of the transistor and to the output of the second amplifier. The R-2R resistor ladder includes a resistor coupled to either the transistor or the output of the second amplifier.

First claim

What is claimed is:

1. A system, comprising:
an integrated circuit, comprising:
a transistor;
a first amplifier coupled to the transistor;
a second amplifier having an output and coupled to the transistor and the first amplifier; and
an R-2R resistor ladder having multiple rungs, each rung switchably coupled to a terminal of the transistor and to the output of the second amplifier, the R-2R resistor ladder including a resistor coupled to either the transistor or the output of the second amplifier.

2. The system of claim 1 , wherein the R-2R resistor ladder includes multiple legs, each of the multiple legs including a different resistor.

3. The system of claim 2 , wherein each of the different resistors has an approximately identical resistance R.

4. The system of claim 2 , wherein each rung of the R-2R resistor ladder includes a different resistor.

5. The system of claim 4 , wherein each of the different resistors has an approximately identical resistance 2R.

6. The system of claim 1 , wherein each of multiple rungs of the R-2R resistor ladder includes a different pair of switches, a first switch in the pair of switches coupled to the terminal of the transistor and a second switch in the pair of switches coupled to the output of the second amplifier.

7. The system of claim 1 , wherein an input of the second amplifier is coupled to an output of the second amplifier.

8. The system of claim 1 , wherein the transistor is a first transistor having a first gate and a first source, and further comprising a second transistor having a second gate and a second source, the first and second gates coupled to each other, and the first and second sources coupled to each other.

9. A circuit, comprising:
a first amplifier having a first amplifier output, a first amplifier input, and a second amplifier input, the first amplifier input of the first amplifier configured to receive a reference voltage;
a transistor having a control terminal and a current terminal, the control terminal coupled to the first amplifier output, the current terminal coupled to the second amplifier input of the first amplifier;
a second amplifier having a second amplifier output, a first amplifier input, and a second amplifier input, the second amplifier output coupled to the first amplifier input of the second amplifier, the second amplifier input of the second amplifier coupled to the current terminal of the first transistor;
a first set of resistors, each resistor in the first set of resistors switchably coupled to the current terminal and to the second amplifier output;
a second set of resistors, a different resistor in the first set of resistors coupled in between each consecutive pair of resistors in the second set of resistors; and
a resistor coupled to the first and second sets of resistors and connected to either the current terminal or to the second amplifier output.

10. The circuit of claim 9 , wherein the current terminal is a first current terminal, and further comprising a second current terminal of the transistor and a current mirror circuit coupled to the second current terminal.

11. The circuit of claim 9 , wherein each resistor in the first set of resistors has an approximately identical resistance 2R.

12. The circuit of claim 11 , wherein the resistor has a resistance of approximately 2R.

13. The circuit of claim 9 , wherein each resistor in the second set of resistors has an approximately identical resistance R.

14. The circuit of claim 9 , wherein the second current terminal and the second amplified output are configured to produce approximately the reference voltage.

15. A circuit, comprising:
a transistor having a control terminal and a current terminal;
an amplifier configured to control current flow through the transistor based on a reference voltage and a voltage on the current terminal of the transistor; and
an R-2R resistor ladder coupled to the current terminal of the transistor with a set of switches,
wherein the amplifier is configured to adjust the current flow through the transistor responsive to a state of the set of switches, and wherein an output of the circuit is based on the current flow through the transistor.

16. The circuit of claim 15 , wherein the amplifier is a first amplifier, and further comprising a second amplifier coupled to the current terminal of the transistor.

17. The circuit of claim 16 , further comprising a first resistor coupled to the transistor and to the R-2R resistor ladder.

18. The circuit of claim 17 , further comprising a second resistor coupled to the R-2R resistor ladder and to either of the transistor or the second amplifier.

19. The circuit of claim 15 , wherein resistors in rungs of the R-2R resistor ladder have resistances of approximately 2R and resistors in legs of the R-2R resistor ladder have resistances of approximately R.

20. The circuit of claim 15 , wherein the R-2R resistor ladder includes multiple rungs configured to carry current in a binary weighted configuration.

21. The circuit of claim 15 , wherein the set of switches is configured to selectively steer current from the R-2R resistor ladder through the transistor based on the state of the set of switches.

22. A system, comprising:
an integrated circuit, comprising:
a transistor;
a first amplifier coupled to the transistor;
a second amplifier coupled to the first amplifier;
a first resistor coupled to the transistor and to the first and second amplifiers; and
an R-2R resistor ladder having multiple rungs, each rung switchably coupled to the first resistor and to an output of the second amplifier, the R-2R resistor ladder including a second resistor coupled to either the first resistor or the output of the second amplifier.

Assignees

• Texas Instruments Inc

Inventors

• Wang Binan

Classifications

• H03M1/1061

  using digitally programmable trimming circuits · CPC title

• H03M1/785 Primary

  using resistors, i.e. R-2R ladders · CPC title

• H03M1/68

  with conversions of different sensitivity, i.e. one conversion relating to the more significant digital bits and another conversion to the less significant bits · CPC title