Driver output pad leakage current compensation

• US 8,742,823 B2
• Filed: 10/05/2011
• Issued: 06/03/2014
• Est. Priority Date: 10/05/2011
• Status: Active Grant

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Goyal, Jagdish Chand, Seth, Sumantra
• Primary Examiner(s): Chen, Sibin
• Application Number:
  US13/253,487
• Publication Number:
  US 20130088276A1
• Time in Patent Office: 972 Days
• Field of Search: 327/362, 327538-543
• US Class Current: 327/362
• CPC Class Codes: G06F 13/4072 Drivers or receivers G06F13/4086 takes precedence; for multistate logic circuits H03K19/0002
• CPC Class Codes: H03F 1/301 in MOSFET amplifiers H03F1/303, H03F1/305, H03F1/308 take precedence

Abstract

A device includes a sense circuit configured to detect a leakage current from a driver output pad. A current mirror responds to the sense circuit and compensates for the leakage current detected at the driver output pad. A scaled compensation circuit can supply compensation current to the current mirror.

Claims

1. A device, comprising:

a sense circuit configured to detect a leakage current from a driver output pad; and

a current mirror configured to respond to the sense circuit and to compensate for the leakage current detected at the driver output pad;

a scaled compensation circuit configured to supply compensation current to the current mirror and to offset the leakage current detected by the sense circuit at the driver output pad;

wherein the scaled compensation circuit, the sense circuit, and the current mirror are configured to compensate for an output driver stage that is pulled to a positive rail voltage; and

wherein the scaled compensation circuit comprises an NMOS pair of transistors that are scaled versions of a driver NMOS output stage.

2. The device of claim 1, wherein the sense circuit comprises an NMOS transistor.

3. The device of claim 1, wherein the current mirror comprises a PMOS transistor pair.

4. A device, comprising:

a sense circuit configured to detect a leakage current from a driver output pad; and

a current mirror configured to respond to the sense circuit and to compensate for the leakage current detected at the driver output pad;

a scaled compensation circuit configured to supply compensation current to the current mirror and to offset the leakage current detected by the sense circuit at the driver output pad;

wherein the scaled compensation circuit, the sense circuit, and the current mirror are configured to compensate for an output driver stage that is pulled to a ground rail voltage; and

wherein the scaled compensation circuit comprises a PMOS pair of transistors that are scaled versions of a driver PMOS output stage.

5. The device of claim 4, wherein the sense circuit comprises a PMOS transistor.

6. The device of claim 4, wherein the current mirror comprises an NMOS transistor pair.

7. An integrated circuit chip, comprising:

a first sense circuit to detect a first leakage current at an output pad when the output pad is pulled to a positive supply rail;

a first scaled compensation circuit to generate a first compensation current based on the detected first leakage current;

a first current mirror to direct the first compensation current to the output pad to counteract the first leakage current;

a second sense circuit to detect a second leakage current at the output pad when the output pad is pulled to a ground rail;

a second scaled compensation circuit to generate a second compensation current based on the detected second leakage current;

a second current mirror to direct the second compensation current to the output pad to counteract the second leakage current; and

the first scaled compensation circuit is an NMOS transistor pair that is scaled according to an NMOS portion of a driver output stage.

8. The integrated circuit chip of claim 7, the second scaled compensation circuit is a PMOS transistor pair that is scaled according to a PMOS portion of a driver output stage.

9. A device, comprising:

a sense circuit configured to detect a leakage current from a driver output pad;

a current mirror configured to respond to the sense circuit and to compensate for the leakage current detected at the driver output pad;

an output driver including first and second transistors having current paths coupled in series between the driver output pad and a first voltage rail; and

a compensation circuit including third and fourth transistors having current paths coupled in series between said sense circuit and said first voltage rail, wherein said third and fourth transistors are scaled versions of said first and second transistors.

10. The device of claim 9, wherein:

said sense circuit includes a fifth transistor having a gate coupled to the driver output pad and a current path coupled between said current mirror and said compensation circuit.

11. The device of claim 10, wherein:

said current mirror includes sixth and seventh transistors having gates coupled together, said sixth transistor having a current path coupled between a second voltage rail and said driver output pad, said seventh transistor having a current path coupled between said second voltage rail and said current path of said fifth transistor.

12. The device of claim 11, wherein said first voltage rail is at ground and said second voltage rail is at a positive voltage.