# US 2014/0153148 A1 · Over voltage protection for a thin oxide load circuit > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2014/0153148 A1 - Document ID: US20140153148A1 - Status: Published application - Kind: A1 - Application number: 13/690,046 - Filed: 2012-11-30 - Published: 2014-06-05 - Earliest claimed: 2012-11-30 - Assignees: Freescale Semiconductor, Inc. - Inventors: XINGHAI TANG; HECTOR SANCHEZ - Web page: https://patentgrep.com/patent/US20140153148A1 ## CPC - H10D 89/811: {using FETs as protective elements} - H02H 9/046: {responsive to excess voltage appearing at terminals of integrated circuits} - Y10T 29/4913: Assembling to base an electrical component, e.g., capacitor, etc. - H10D: INORGANIC ELECTRIC SEMICONDUCTOR DEVICES - 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) - Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION ## Abstract An IC includes: a substrate having a thick oxide portion and a thin oxide portion; a load circuit disposed on the thin oxide portion and coupled between a supply node and a virtual supply node; and a current source circuit and protection circuit disposed on the substrate. The current source circuit has an output coupled to the virtual supply node and is operable to provide a voltage at the virtual supply node. The protection circuit includes a sensing portion and a protection portion. The sensing portion is coupled to the virtual supply node and is operable to detect the voltage at the virtual supply node. The protection portion is coupled to the sensing portion and is operable, in response to the sensed voltage, to prevent a difference in voltage between the voltage at the virtual supply node and a second voltage at the supply node from exceeding a maximum voltage. ## Claims ### Claim 1 An integrated circuit that provides over voltage protection for a thin oxide load circuit, the integrated circuit comprising: a substrate having a thick oxide portion and a thin oxide portion; a load circuit disposed on the thin oxide portion, wherein the load circuit is coupled between a supply node and a virtual supply node; a current source circuit disposed on the substrate, the current source circuit having an input coupled to a control signal node and an output coupled to the virtual supply node, wherein the current source circuit is operable to provide a voltage at the virtual supply node, which is based on a control signal coupled to the control signal node; a protection circuit disposed on the substrate, the protection circuit comprising a sensing portion and a protection portion, wherein the sensing portion is coupled to the virtual supply node and is operable to sense the voltage at the virtual supply node, and the protection portion is coupled to the sensing portion and is operable, in response to feedback from the sensing portion of the sensed voltage, to prevent a difference in voltage between the voltage at the virtual supply node and a second voltage at the supply node from exceeding a first maximum voltage value. ### Claim 2 (depends on 1) The integrated circuit of claim 1, wherein the load circuit comprises a ring oscillator that includes a chain of an odd number of inverters, wherein each inverter has a first terminal connected to the supply node and a second terminal connected to the virtual supply node. ### Claim 3 (depends on 2) The integrated circuit of claim 2, wherein the ring oscillator comprises a single-ended oscillator or a differential oscillator. ### Claim 4 (depends on 2) The integrated circuit of claim 2, wherein the ring oscillator comprises three inverters. ### Claim 5 (depends on 1) The integrated circuit of claim 1, wherein the protection circuit is disposed on the thin oxide portion or the thick oxide portion of the substrate. ### Claim 6 (depends on 1) The integrated circuit of claim 1, wherein the protection circuit comprises a diode having a first terminal coupled to the virtual supply node and a second terminal coupled to the supply node or to a maximum voltage node that is configured to receive a second maximum voltage value. ### Claim 7 (depends on 1) The integrated circuit of claim 1, wherein the protection circuit comprises a diode-connected transistor comprising a first terminal connected to the virtual supply node and a second and third terminal coupled to the supply node or to a maximum voltage node that is configured to receive a second maximum voltage value. ### Claim 8 (depends on 7) The integrated circuit of claim 7, wherein the diode-connected transistor comprises an N-channel Metal Oxide Semiconductor transistor or a P-channel Metal Oxide Semiconductor transistor. ### Claim 9 (depends on 7) The integrated circuit of claim 7, wherein the second terminal comprises a gate terminal, and the second and third terminal are connected together and connected to the supply node or to the maximum voltage node. ### Claim 10 (depends on 7) The integrated circuit of claim 7, wherein the second terminal comprises a gate terminal, and wherein the integrated circuit further comprises a Complementary Metal-Oxide Semiconductor (CMOS) transmission gate connected between the gate terminal and the supply node or the maximum voltage node to control conductivity of the diode-connected transistor using first and second enabling voltages. ### Claim 11 (depends on 1) The integrated circuit of claim 1, wherein the sensing portion of the protection circuit comprises a comparator having a first input terminal connected to the virtual supply node, a second input terminal connected to a voltage reference node that is configured to receive a reference voltage, and an output terminal. ### Claim 12 (depends on 11) The integrated circuit of claim 11, wherein the protection portion of the protection circuit comprises a transistor having a gate terminal connected to the output terminal of the comparator, a second terminal connected to the supply node and a third terminal connected to the virtual supply node. ### Claim 13 (depends on 11) The integrated circuit of claim 11 further comprising a resistor connected between the supply node and a supply input node, wherein the protection portion of the protection circuit comprises a transistor having a gate terminal connected to the output terminal of the comparator, a second terminal connected to the supply node and a third terminal connected to a second supply node. ### Claim 14 (depends on 11) The integrated circuit of claim 11, wherein the protection portion of the protection circuit comprises a first inverter having an input terminal connected to the output terminal of the comparator and an output terminal connected to the control signal node and a second inverter having an input terminal connected to the output terminal of the first inverter, wherein the second inverter is operative to provide an alert signal. ### Claim 15 (depends on 11) The integrated circuit of claim 11, wherein the protection portion of the protection circuit comprises: a first inverter having an input terminal connected to the output terminal of the comparator and an output terminal; a Complementary Metal-Oxide Semiconductor (CMOS) transmission gate connected between the virtual supply node and a maximum voltage node that is configured to receive a second maximum voltage value, the CMOS transmission gate comprising a first gate terminal connected to the output terminal of the comparator and a second gate terminal connected to the output terminal of the first inverter; and a second inverter having an input terminal connected to the output terminal of comparator, wherein the second inverter is operative to provide an alert signal. ### Claim 16 (depends on 1) The integrated circuit of claim 1, wherein the current source circuit comprises an N-channel Metal Oxide Semiconductor transistor or a P-channel Metal Oxide Semiconductor transistor having a gate terminal connected to the control signal node, a second terminal connected to the virtual supply node and a third terminal connected to a second supply node. ### Claim 17 A method of fabricating an integrated circuit on a substrate having a thick oxide portion and a thin oxide portion, the method comprising: forming a load circuit on the thin oxide portion of the substrate, wherein the load circuit is coupled between a supply node and a virtual supply node; forming a current source circuit on the substrate, the current source circuit having an input coupled to a control signal node and an output coupled to the virtual supply node, wherein the current source circuit is operable to provide a voltage at the virtual supply node, which is based on a control signal coupled to the control signal node; forming a protection circuit on the substrate, the protection circuit comprising a sensing portion and a protection portion, wherein the sensing portion is coupled to the virtual supply node and is operable to sense the voltage at the virtual supply node, and the protection portion is coupled to the sensing portion and is operable, in response to feedback from the sensing portion of the sensed voltage, to prevent a difference in voltage between the voltage at the virtual supply node and a second voltage at the supply node from exceeding a first maximum voltage value. ### Claim 18 (depends on 17) The method of claim 17, wherein the integrated circuit is fabricated using a Complementary Metal-Oxide Semiconductor process. ### Claim 19 (depends on 18) The method of claim 18, wherein: forming the current source circuit on the substrate comprises forming on the thick oxide portion of the substrate an N-channel Metal Oxide Semiconductor transistor or a P-channel Metal Oxide Semiconductor transistor having a gate terminal connected to the control signal node, a second terminal connected to the virtual supply node and a third terminal connected to a second supply node; forming the protection circuit on the substrate comprises forming the protection circuit on the thick oxide portion of the substrate. ### Claim 20 (depends on 17) The method of claim 17, wherein forming the load circuit on the thin oxide portion of the substrate comprises forming a ring oscillator that includes a chain of an odd number of inverters, wherein each inverter has a first terminal connected to the supply node and a second terminal connected to the virtual supply node.