# US 8,570,694 B2 · Low voltage electrostatic discharge protection > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,570,694 B2 - Document ID: US8570694B2 - Status: Granted - Kind: B2 - Application number: 13/121,987 - Filed: 2009-10-07 - Published: 2012-03-29 - Granted: 2013-10-29 - Earliest claimed: 2008-10-31 - Assignees: Cambridge Silicon Radio Limited - Applicants: William Pugsley - Inventors: William Pugsley - Web page: https://patentgrep.com/patent/US8570694B2 ## CPC - H02H 9/046: {responsive to excess voltage appearing at terminals of integrated circuits} - H02H 9/005: {avoiding undesired transient conditions} - H02H: EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS (indicating or signalling undesired working conditions G01R, e.g. G01R31/00, G08B; locating faults along lines G01R31/08; emergency protective devices H01H) ## Abstract A protection circuit for protecting components from an electrostatic discharge at a node in an integrated circuit having a first set of electronic components of a first voltage sensitivity, the protection circuit comprising: detection circuitry arranged to detect an electrostatic discharge at the node; a first switching device connected between the first set of components and the node; and a second switching device connected between the node and ground; wherein, when an electrostatic discharge is detected at the node, the first switching device is configured to isolate the first set of components from the node and the second switching device is configured to provide a current path from said node to ground. ## Claims ### Claim 1 A protection circuit for protecting components from an electrostatic discharge at a first node in an integrated circuit having a first set of electronic components, the first set of electronic components having a first voltage sensitivity, the first set of electronic components being supplied with a voltage supply by a second node, the protection circuit comprising: a first switching device connected between the first node and the second node; a second switching device connected between the first node and ground; a third switching device connected between the second node and ground; and detection circuitry arranged to detect an electrostatic discharge at the first node and in response to said detection, to control the switching devices such that: the first switching device is switched off to isolate the first set of electronic components from the first node, the second switching device provides a current path from the first node to ground, and the third switching device provides a current path between the second node and ground, bypassing the first set of components. ### Claim 2 (depends on 1) A protection circuit as claimed in claim 1, wherein the first node is a power supply rail. ### Claim 3 (depends on 1) A protection circuit as claimed in claim 1, wherein the first node is a contact of the integrated circuit. ### Claim 4 (depends on 1) A protection circuit as claimed in claim 1, wherein the second switching device is configured to hold the voltage at the first node at an overvoltage during an electrostatic discharge. ### Claim 5 (depends on 4) A protection circuit as claimed in claim 4, wherein the overvoltage exceeds the operating voltage of the integrated circuit. ### Claim 6 (depends on 5) A protection circuit as claimed in claim 5, wherein the overvoltage is at least 50 percent higher than the operating voltage of the integrated circuit. ### Claim 7 (depends on 4) A protection circuit as claimed in claim 4, wherein the overvoltage exceeds the maximum voltage to which the first set of electronic components are tolerant. ### Claim 8 (depends on 7) A protection circuit as claimed in claim 7, wherein the maximum voltage to which the first set of electronic components are tolerant is the greatest voltage which can be supported across the first set of components for the duration of an ESD event. ### Claim 9 (depends on 7) A protection circuit as claimed in claim 7, wherein the maximum voltage to which the first set of electronic components are tolerant is the maximum rated voltage of the components of the first set. ### Claim 10 (depends on 1) A protection circuit as claimed in claim 1, wherein the integrated circuit further comprises a second set of electronic components, the second set of electronic components having a second voltage sensitivity connected between the first node and ground. ### Claim 11 (depends on 10) A protection circuit as claimed in claim 10, wherein the maximum voltage at the first node to which the second set of electronic components are tolerant is higher than the maximum voltage at the first node to which the first set of components are tolerant. ### Claim 12 (depends on 11) A protection circuit as claimed in claim 11, wherein the maximum voltage at the first node to which the second set of electronic components are tolerant is the greatest voltage which can be supported across the second set of components for the duration of an ESD event. ### Claim 13 (depends on 10) A protection circuit as claimed in claim 10, wherein the second switching device is configured to hold the voltage at the first node at an overvoltage during an electrostatic discharge, wherein the overvoltage does not exceed the maximum voltage to which the second set of electronic components are tolerant. ### Claim 14 (depends on 10) A protection circuit as claimed in claim 10, wherein the first set of electronic components includes transistors having single-oxide gates and the second set of electronic components includes transistors having double-oxide gates. ### Claim 15 (depends on 1) A protection circuit as claimed in claim 1, wherein the first and second switching devices are transistors of opposite polarity. ### Claim 16 (depends on 1) A protection circuit as claimed in claim 1, wherein the detection circuitry is configured to detect an electrostatic discharge at the first node by detecting when the voltage at the first node exceeds a predetermined voltage. ### Claim 17 (depends on 1) A protection circuit as claimed in claim 1, wherein the detection circuitry is configured to detect an electrostatic discharge at the first node by detecting when the rate of increase of the voltage at the first node exceeds a predetermined rate. ### Claim 18 (depends on 1) A protection circuit as claimed in claim 1, wherein the detection circuitry is configured to provide a trigger voltage at its output when an electrostatic discharge is detected at the first node. ### Claim 19 (depends on 18) A protection circuit as claimed in claim 18, wherein the first switching device is a transistor and the base or gate of the first switching device is coupled to the output from the detection circuitry. ### Claim 20 (depends on 18) A protection circuit as claimed in claim 18, wherein the second switching device is a transistor the base or gate of the second switching device is coupled to the output from the detection circuitry. ### Claim 21 (depends on 18) A protection circuit as claimed in claim 18, wherein the third switching device is a transistor and the base or gate of the third switching device is coupled to the output from the detection circuitry.