# US 7,609,121 B2 · Multiple status e-fuse based non-volatile voltage control oscillator configured for process variation compensation, an associated method and an associated design structure > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 7,609,121 B2 - Document ID: US7609121B2 - Status: Granted - Kind: B2 - Application number: 12/057,494 - Filed: 2008-03-28 - Published: 2009-10-01 - Granted: 2009-10-27 - Earliest claimed: 2008-03-28 - Assignees: International Business Machines Corporation - Inventors: Kai D. Feng; Kafai Lai; Ping-Chuan Wang; Zhijian J. Yang - Web page: https://patentgrep.com/patent/US7609121B2 ## CPC - H03B 5/1206: {using multiple transistors for amplification} - H03B 5/1243: {the means comprising voltage variable capacitance diodes} - H03B: GENERATION OF OSCILLATIONS, DIRECTLY OR BY FREQUENCY-CHANGING, BY CIRCUITS EMPLOYING ACTIVE ELEMENTS WHICH OPERATE IN A NON-SWITCHING MANNER; GENERATION OF NOISE BY SUCH CIRCUITS (generators adapted for electrophonic musical instruments G10H; masers or lasers H01S; generation of oscillations in plasma H05H) ## Abstract Disclosed are embodiments of a voltage controlled oscillator (VCO) capable of non-volatile self-correction to compensate for process variations and to ensure that the center frequency of the oscillator is maintained within a predetermined frequency range. This VCO incorporates a pair of varactors connected in parallel to an inductor-capacitor (LC) tank circuit for outputting a periodic signal having a frequency that is proportional to an input voltage. A control loop uses a programmable variable resistance e-fuse to set a compensation voltage to be applied to the pair of varactors. By adjusting the compensation voltage, the capacitance of the pair of varactors can be adjusted in order to selectively increase or decrease the frequency of the periodic signal in response to a set input voltage and, thereby to bring the frequency of that periodic signal into the predetermined frequency range. Also disclosed are embodiments of an associated design structure for such a VCO and an associated method for operating such a VCO. ## Claims ### Claim 1 A method for operating a voltage controlled oscillator, said method comprising: providing a voltage controlled oscillator comprising an inductor-capacitor (LC) tank circuit adapted to receive a first voltage and at least one varactor connected in parallel with said inductor-capacitor (LC) tank circuit and adapted to receive a second voltage, wherein said voltage controlled oscillator is further adapted to output a periodic signal a having a frequency that is a function of said first voltage and said second voltage; determining if said frequency is within a predetermined frequency range; and if said frequency is outside said predetermined frequency range, selectively programming resistance in a variable resistance e-fuse electrically connected to said at least one varactor so as to selectively adjust said second voltage at said at least one varactor, so as to selectively adjust capacitance of said at least one varactor, and further so as to bring said frequency to within said predetermined frequency range. ### Claim 2 (depends on 1) The method according to claim 1, wherein said determining if said frequency is within said predetermined frequency range comprises: determining a period of said periodic signal; converting said period into an output voltage; and determining if said output voltage is within a predetermined voltage range, and wherein said selectively programming said resistance comprises selectively adjusting said second voltage, when said output voltage is outside said predetermined voltage range, so as to bring said frequency to within said predetermined frequency range. ### Claim 3 (depends on 2) The method according to claim 2, wherein said selectively programming said resistance further comprises: selectively increasing said resistance so as to increase said second voltage in order to decrease said capacitance and, thereby increase said frequency, when said output voltage is higher than said predetermined voltage range; and selectively decreasing said resistance so as to selectively decrease said second voltage in order to increase said capacitance, thereby decrease said frequency, when said output voltage is lower than said predetermined voltage range. ### Claim 4 (depends on 1) The method according to claim 1, wherein said variable resistance e-fuse comprises: a conductor; a plurality of series connected resistors; a plurality of contacts on said conductor connected to said plurality of said series connected resistors; a first sensing node and a second sensing node on opposite ends of said series connected resistors, wherein said first said sensing node is electrically connected to said at least one varactor for applying said second voltage to said at least one varactor and said second sensing node is electrically connected to ground; and a first programming node and a second programming node on opposite ends of said conductor, and wherein said selectively programming said resistance further comprises selectively controlling current flow through said conductor between said first programming node and said second programming node such that said contacts one of become opens in sequence to increase said resistance and revert back to shorts in sequence to decrease said resistance. ### Claim 5 (depends on 4) The method according to claim 4, wherein said resistors are all equal in size. ### Claim 6 (depends on 4) The method according claim 4, further comprising fine tuning said frequency using a plurality of said variable resistance e-fuses connected in series, wherein all of said resistors in any given variable resistance e-fuse are equal in size and wherein said resistors on adjacent variable resistance e-fuses are progressively smaller in size. ### Claim 7 (depends on 1) The method according to claim 1, further comprising: using a first current source to generate said second voltage and using a second current source different from said first current source to program said resistance. ### Claim 8 A method for operating a voltage controlled oscillator, said method comprising: providing a voltage controlled oscillator comprising an inductor-capacitor (LC) tank circuit adapted to receive a first voltage and at least one varactor connected in parallel with said inductor-capacitor (LC) tank circuit and adapted to receive a second voltage, wherein said voltage controlled oscillator is further adapted to output a periodic signal a having a frequency that is a function of said first voltage and said second voltage; determining if said frequency is within a predetermined frequency range; and if said frequency is outside said predetermined frequency range, selectively programming resistance in a variable resistance e-fuse electrically connected to said at least one varactor so as to selectively adjust said second voltage at said at least one varactor, so as to selectively adjust capacitance of said at least one varactor, and further so as to bring said frequency to within said predetermined frequency range, wherein said determining if said frequency is within said predetermined frequency range comprises: determining a period of said periodic signal; converting said period into an output voltage; and determining if said output voltage is within a predetermined voltage range, and wherein said selectively programming said resistance comprises selectively adjusting said second voltage, when said output voltage is outside said predetermined voltage range, so as to bring said frequency to within said predetermined frequency range. ### Claim 9 (depends on 8) The method according to claim 8, wherein said selectively programming said resistance further comprises: selectively increasing said resistance so as to increase said second voltage in order to decrease said capacitance and, thereby increase said frequency, when said output voltage is higher than said predetermined voltage range; and selectively decreasing said resistance so as to selectively decrease said second voltage in order to increase said capacitance, thereby decrease said frequency, when said output voltage is lower than said predetermined voltage range. ### Claim 10 (depends on 8) The method according to claim 8, wherein said variable resistance e-fuse comprises: a conductor; a plurality of series connected resistors; a plurality of contacts on said conductor connected to said plurality of said series connected resistors; a first sensing node and a second sensing node on opposite ends of said series connected resistors, wherein said first said sensing node is electrically connected to said at least one varactor for applying said second voltage to said at least one varactor and said second sensing node is electrically connected to ground; and a first programming node and a second programming node on opposite ends of said conductor, and wherein said selectively programming said resistance further comprises selectively controlling current flow through said conductor between said first programming node and said second programming node such that said contacts one of become opens in sequence to increase said resistance and revert back to shorts in sequence to decrease said resistance. ### Claim 11 (depends on 10) The method according to claim 10, wherein said resistors are all equal in size. ### Claim 12 (depends on 10) The method according claim 10, further comprising fine tuning said frequency using a plurality of said variable resistance e-fuses connected in series, wherein all of said resistors in any given variable resistance e-fuse are equal in size and wherein said resistors on adjacent variable resistance e-fuses are progressively smaller in size. ### Claim 13 (depends on 8) The method according to claim 8, further comprising: using a first current source to generate said second voltage and using a second current source different from said first current source to program said resistance. ### Claim 14 A method for operating a voltage controlled oscillator, said method comprising: providing a voltage controlled oscillator comprising an inductor-capacitor (LC) tank circuit adapted to receive a first voltage and at least one varactor connected in parallel with said inductor-capacitor (LC) tank circuit and adapted to receive a second voltage, wherein said voltage controlled oscillator is further adapted to output a periodic signal a having a frequency that is a function of said first voltage and said second voltage; determining if said frequency is within a predetermined frequency range; and if said frequency is outside said predetermined frequency range, selectively programming resistance in a variable resistance e-fuse electrically connected to said at least one varactor so as to selectively adjust said second voltage at said at least one varactor, so as to selectively adjust capacitance of said at least one varactor, and further so as to bring said frequency to within said predetermined frequency range, wherein said variable resistance e-fuse comprises: a conductor; a plurality of series connected resistors; a plurality of contacts on said conductor connected to said plurality of said series connected resistors; a first sensing node and a second sensing node on opposite ends of said series connected resistors, wherein said first said sensing node is electrically connected to said at least one varactor for applying said second voltage to said at least one varactor and said second sensing node is electrically connected to ground; and a first programming node and a second programming node on opposite ends of said conductor, and wherein said selectively programming said resistance further comprises selectively controlling current flow through said conductor between said first programming node and said second programming node such that said contacts one of become opens in sequence to increase said resistance and revert back to shorts in sequence to decrease said resistance. ### Claim 15 (depends on 14) The method according to claim 14, wherein said determining if said frequency is within said predetermined frequency range comprises: determining a period of said periodic signal; converting said period into an output voltage; and determining if said output voltage is within a predetermined voltage range, and wherein said selectively programming said resistance comprises selectively adjusting said second voltage, when said output voltage is outside said predetermined voltage range, so as to bring said frequency to within said predetermined frequency range. ### Claim 16 (depends on 15) The method according to claim 15, wherein said selectively programming said resistance further comprises: selectively increasing said resistance so as to increase said second voltage in order to decrease said capacitance and, thereby increase said frequency, when said output voltage is higher than said predetermined voltage range; and selectively decreasing said resistance so as to selectively decrease said second voltage in order to increase said capacitance, thereby decrease said frequency, when said output voltage is lower than said predetermined voltage range. ### Claim 17 (depends on 14) The method according to claim 14, wherein said resistors are all equal in size. ### Claim 18 (depends on 14) The method according claim 14, further comprising fine tuning said frequency using a plurality of said variable resistance e-fuses connected in series, wherein all of said resistors in any given variable resistance e-fuse are equal in size and wherein said resistors on adjacent variable resistance e-fuses are progressively smaller in size. ### Claim 19 (depends on 14) The method according to claim 14, further comprising: using a first current source to generate said second voltage and using a second current source different from said first current source to program said resistance.