DYNAMIC TRIGGER VOLTAGE CONTROL FOR AN ESD PROTECTION DEVICE

• US 20170194788A1
• Filed: 12/30/2015
• Published: 07/06/2017
• Est. Priority Date: 12/30/2015
• Status: Active Grant

• Current Assignee: Silicon Laboratories Incorporated
• Original Assignee: Silicon Laboratories Incorporated
• Inventors: Smith, Jeremy C.
• Granted Patent: US 10,063,048 B2
• Time in Patent Office: Days
• CPC Class Codes: H01L 27/0259 using bipolar transistors as protective elements
• CPC Class Codes: H01L 27/0262 including a PNP transistor and a NPN transistor, wherein each of said transistors has its base coupled to the collector of the other transistor, e.g. silicon controlled rectifier [SCR] devices
• CPC Class Codes: H01L 27/0266 using field effect transistors as protective elements
• CPC Class Codes: H01L 27/0292 using a specific configuration of the conducting means connecting the protective devices, e.g. ESD buses
• CPC Class Codes: H01L 29/7393 Insulated gate bipolar mode transistors, i.e. IGBT; IGT; COMFET
• CPC Class Codes: H01L 29/7394 on an insulating layer or substrate, e.g. thin film device or device isolated from the bulk substrate H01L29/7398 takes precedence
• CPC Class Codes: H02H 9/044 Physical layout, materials not provided for elsewhere varistors H01C7/12; spark-gaps H01T; Ovshinsky devices H10N70/00
• CPC Class Codes: H02H 9/046 responsive to excess voltage appearing at terminals of integrated circuits protection by specific structural integration design H01L27/0248

Abstract

Circuit configurations and related methods are provided that may be implemented using insulated-gate bipolar transistor (IGBT) device circuitry to protect at risk circuitry (e.g., such as high voltage output buffer circuitry or any other circuitry subject to undesirable ESD events) from damage due to ESD events that may occur during system assembly. The magnitude of the trigger voltage V_T1 threshold for an IGBT ESD protection device may be dynamically controlled between at least two different values so that trigger voltage V_T1 threshold for an IGBT ESD protection device may be selectively reduced when needed to better enable ESD operation.

Claims

1. A semiconductor circuit device, comprising:

a signal pad;

a first supply rail;

an insulated-gate bipolar transistor (IGBT) device coupled to form an embedded parasitic silicon controlled rectifier (SCR) between the signal pad and the first supply rail;

a resistor coupled in a first current path between a gate of the IGBT device and the first supply rail;

a switching element coupled in a second current path between the gate of the IGBT device and the first supply rail, the second current path being parallel to the first current path;

where the switching element is configured to selectively couple the gate of the IGBT device to the first supply rail through the second current path to lower a resistance to current flow between the gate of the IGBT device and the first supply rail.

2. The circuit device of claim 1, where the IGBT device is configured to turn on to discharge current between the signal pad and the first supply rail only when a voltage between the signal pad and the first supply rail is greater than or equal to a trigger voltage threshold, the trigger voltage threshold being lower when the gate of the IGBT device is not coupled to the first supply rail by the switching element through the second current path than when the gate of the IGBT device is coupled to first supply rail through the second current path.

3. The circuit device of claim 1, further comprising an additional supply rail of opposite polarity to the first supply rail, the additional supply rail being coupled to the switching element, and the switching element being configured to turn on when at least one of the first and additional supply rails is powered relative to the other supply rail.

4. The circuit device of claim 1, further comprising:

a second supply rail of opposite polarity to the first supply rail;

output buffer circuitry coupled between the first and second supply rails, the signal pad being coupled to the output buffer circuitry;

where the IGBT device is configured to turn on to discharge current between the signal pad and the first supply rail only when a voltage between the signal pad and the first supply rail is greater than or equal to a trigger voltage threshold; and

where the switching element is configured to selectively couple the gate of the IGBT device to the first supply rail through the second current path to raise the trigger voltage threshold of the IGBT device.

5. The circuit device of claim 1, where the first supply rail is a negative supply rail;

where the IGBT circuit is a N-channel insulated-gate bipolar transistor (NiGBT) device; and

where the circuit device further comprises;

a second supply rail that is a positive supply rail; and

output buffer circuitry coupled between the positive and negative supply rails, the signal pad being coupled to the output buffer circuitry;

6. The circuit device of claim 5, further comprising a third supply rail coupled to the switching element, the third supply rail being a positive supply rail of lower positive voltage than the second supply rail and that is powered together with the second supply rail when the output buffer circuitry is powered on;

and where the switching element is configured to turn on when the third supply rail is powered on to selectively couple the gate of the NiGBT device to the first supply rail through the second current path to raise the trigger voltage threshold of the NiGBT device, and is is configured to turn off when the third supply rail is powered off to selectively decouple the gate of the NiGBT device from the first supply rail through the second current path to lower the trigger voltage threshold of the NiGBT device.

7. The circuit device of claim 5, where the second supply rail has an operating voltage when the second supply rail is powered on;

where a trigger voltage threshold of the NiGBT device is higher than the operating voltage of the second supply rail when the switching element is turned on to couple the gate of the NiGBT device to the first supply rail through the second current path; and

where the the trigger voltage of the NiGBT device is less than the operating voltage of the second supply rail when the gate of the NiGBT device is not coupled by the switching element to the first supply rail through the second current path.

8. The circuit device of claim 1, where a channel length of the IGBT device is about 0.9 microns.

9. The circuit device of claim 1, where the IGBT device is configured to respond to occurrence of an electrostatic discharge (ESD) event on the signal pad by discharging current between the signal pad and the first supply rail.

10. A method, comprising:

operating a semiconductor circuit device that comprises an insulated-gate bipolar transistor (IGBT) device that is coupled to form an embedded parasitic silicon controlled rectifier (SCR) between a signal pad and a first supply rail of a circuit device, a resistor being coupled in a first current path between a gate of the IGBT device and the first supply rail, and a switching element being coupled in a second current path between the gate of the IGBT device and the first supply rail such that the second current path is parallel to the first current path; and

using the switching element to selectively couple the gate of the IGBT device to the first supply rail through the second current path to lower a resistance to current flow between the gate of the IGBT device and the first supply rail.

11. The method of claim 10, further comprising using the IGBT device to turn on to discharge current between the signal pad and the first supply rail only when a voltage between the signal pad and the first supply rail is greater than or equal to a trigger voltage threshold, the trigger voltage threshold being lower when the gate of the IGBT device is not coupled to the first supply rail by the switching element through the second current path than when the gate of the IGBT device is coupled to first supply rail through the second current path.

12. The method of claim 10, where the semiconductor circuit device further comprises an additional supply rail of opposite polarity to the first supply rail, the additional supply rail being coupled to the switching element;

and where the method further comprises using the switching element to turn on when at least one of the first and additional supply rails is powered relative to the other supply rail.

13. The method of claim 10, where the semiconductor circuit device further comprises a second supply rail of opposite polarity to the first supply rail, and output buffer circuitry coupled between the first and second supply rails with the signal pad being coupled to the output buffer circuitry;

and where the method further comprises;

using the IGBT device to turn on to discharge current between the signal pad and the first supply rail only when a voltage between the signal pad and the first supply rail is greater than or equal to a trigger voltage threshold; and

using the switching element to selectively couple the gate of the IGBT device to the first supply rail through the second current path to raise the trigger voltage threshold of the IGBT device.

14. The method of claim 10, where the first supply rail is a negative supply rail;

where the IGBT device is a N-channel insulated-gate bipolar transistor (NiGBT) device; and

where the semiconductor circuit device further comprises;

a second supply rail that is a positive supply rail; and

output buffer circuitry coupled between the positive and negative supply rails, the signal pad being coupled to the output buffer circuitry;

15. The method of claim 14, where the semiconductor circuit device further comprises a third supply rail coupled to the switching element, the third supply rail being a positive supply rail of lower positive voltage than the second supply rail and that is powered together with the second supply rail when the output buffer circuitry is powered on;

and where the method further comprises;

using the switching element to turn on when the third supply rail is powered on to selectively couple the gate of the NiGBT device to the first supply rail through the second current path to raise the trigger voltage threshold of the NiGBT device; and

using the switching element to turn off when the third supply rail is powered off to selectively decouple the gate of the NiGBT device from the first supply rail through the second current path to lower the trigger voltage threshold of the NiGBT device.

16. The method of claim 14, where the second supply rail has an operating voltage when the second supply rail is powered on;

where a trigger voltage threshold of the NiGBT device is higher than the operating voltage of the second supply rail when the switching element is turned on to couple the gate of the NiGBT device to the first supply rail through the second current path; and

where the the trigger voltage of the NiGBT device is less than the operating voltage of the second supply rail when the gate of the NiGBT device is not coupled by the switching element to the first supply rail through the second current path.

17. The method of claim 10, where a channel length of the IGBT device is about 0.9 microns.

18. The method of claim 10, further comprising using the IGBT device to respond to occurrence of an electrostatic discharge (ESD) event on the signal pad by discharging current between the signal pad and the first supply rail.

19. The method of claim 10, further comprising performing the following steps prior to operating the semiconductor circuit device:

first empirically testing the IGBT device configuration to determine a relationship between multiple different resistance values coupled in the first current path and corresponding different trigger voltage thresholds at which the IGBT device turns on to discharge current between the signal pad and the first supply rail; and

then using the determined relationship to select a particular resistance value for the resistor coupled in the first current path that results in a desired trigger voltage threshold for the IGBT device.