# US 8,570,684 B1 · Implementing integrated spin-torque oscillator and interface bias control for hard disk drives > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,570,684 B1 - Document ID: US8570684B1 - Status: Granted - Kind: B1 - Application number: 13/646,614 - Filed: 2012-10-05 - Granted: 2013-10-29 - Earliest claimed: 2012-10-05 - Assignees: HGST Netherlands B.V. - Applicants: HGST Netherlands B.V. - Inventors: John Thomas Contreras; Ikuya Tagawa; Albert John Wallash - Web page: https://patentgrep.com/patent/US8570684B1 ## CPC - G11B 5/02: Recording, reproducing, or erasing methods; Read, write or erase circuits therefor - G11B 2005/0024: {Microwave assisted recording} - G11B: INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER (recording measured values in a way that does not require playback through a transducer G01D9/00; recording or playback apparatus using mechanically marked tape, e.g. punched paper tape, or using unit records, e.g. punched or magnetically marked cards G06K; transferring data from one type of record carrier to another G06K1/18; circuits for coupling output of reproducer to radio receiver H04B1/20; gramophone pick-ups or like acoustic electromechanical transducers or circuits therefor H04R) ## Abstract A method, apparatus, and system for implementing spin integrated spin-torque oscillator (STO) with an interface bias control for hard disk drives. Bias circuitry for a spin-torque oscillator (STO) is integrated with a slider for microwave assisted magnetic recording (MAMR). The slider includes read and write transducers and the integrated STO bias circuitry controls a bias potential applied to a write return pole to the write transducer with respect to a disk. ## Claims ### Claim 1 A method for implementing an integrated spin-torque oscillator (STO) with an interface bias control for hard disk drives comprising: providing integrated bias circuitry for the spin-torque oscillator (STO) coupled a slider for microwave assisted magnetic recording (MAMR); providing a read transducer and a write transducer with the slider; said write transducer including a write pole and a write return pole; and controlling a bias potential applied to said write return pole with respect to a disk media with said integrated STO bias circuitry. ### Claim 2 (depends on 1) The method as recited in claim 1 includes providing a spin-torque oscillator (STO) element coupled between said write pole and said write return pole. ### Claim 3 (depends on 1) The method as recited in claim 1 wherein providing integrated bias circuitry for the spin-torque oscillator (STO) coupled a slider for microwave assisted magnetic recording (MAMR includes implementing said integrated STO bias circuitry in a Read/Write integrated circuit (IC). ### Claim 4 (depends on 1) The method as recited in claim 1 wherein providing integrated bias circuitry for the spin-torque oscillator (STO) coupled a slider for microwave assisted magnetic recording (MAMR) includes implementing said integrated STO bias circuitry with at least one slider connection to an ISB bias line. ### Claim 5 (depends on 1) The method as recited in claim 1 wherein providing integrated bias circuitry for the spin-torque oscillator (STO) coupled a slider for microwave assisted magnetic recording (MAMR) includes providing a slider connection with high-frequency low-impedance path to the system ground. ### Claim 6 (depends on 1) The method as recited in claim 1 wherein providing integrated bias circuitry for the spin-torque oscillator (STO) coupled a slider for microwave assisted magnetic recording (MAMR) includes providing at least one slider connection with a transducer connection to a common potential connecting to an ISB bias line and voltage potential. ### Claim 7 (depends on 1) The method as recited in claim 1 wherein controlling said bias potential applied to said write return pole with respect to said disk with said integrated STO bias circuitry includes providing a controllable bias potential with respect to media of less than one Volt, to prevent head-to-disk breakdown electrostatic discharge (ESD) damage. ### Claim 8 (depends on 1) The method as recited in claim 1 wherein controlling said bias potential applied to said write return pole with respect to said disk with said integrated STO bias circuitry includes providing current limit protection for conductive asperities to the disk. ### Claim 9 (depends on 1) The method as recited in claim 1 wherein controlling said bias potential applied to said write return pole with respect to said disk with said integrated STO bias circuitry includes providing a voltage offset resistor bias to said write pole. ### Claim 10 (depends on 1) The method as recited in claim 1 wherein controlling said bias potential applied to said write return pole with respect to said disk with said integrated STO bias circuitry includes providing an independent STO bias potential coupled by an independent STO pad connected to said write pole. ### Claim 11 An apparatus for implementing an integrated spin-torque oscillator (STO) with an interface bias control for hard disk drives comprising: a slider including a read transducer and a write transducer; said write transducer including a write pole and a write return pole; the spin-torque oscillator (STO) integrated with said slider for microwave assisted magnetic recording (MAMR); STO bias circuitry coupled to said slider and controlling a bias potential applied to said write return pole with respect to a disk media with said integrated STO bias circuitry. ### Claim 12 (depends on 11) The apparatus as recited in claim 11 includes a spin-torque oscillator (STO) element coupled between said write pole and said write return pole. ### Claim 13 (depends on 11) The apparatus as recited in claim 11 includes a Read/Write integrated circuit (IC) implementing said integrated STO bias circuitry. ### Claim 14 (depends on 11) The apparatus as recited in claim 11 wherein said integrated STO bias circuitry includes at least one slider connection to an ISB bias line. ### Claim 15 (depends on 11) The apparatus as recited in claim 11 wherein said integrated STO bias circuitry includes a slider connection with high-frequency low-impedance path to the system ground. ### Claim 16 (depends on 11) The apparatus as recited in claim 11 wherein said integrated STO bias circuitry includes a pair of transconductance amplifiers with current biases and feedback for providing adjustability of loop gain, and characteristic changes for output impedance and bandwidth. ### Claim 17 (depends on 16) The apparatus as recited in claim 16 wherein said integrated STO bias circuitry includes an overall Laplace transfer function represented by Vsbd/Vin=(gm1R1gm2R2)/(R1C1s+gm1R1gm2R2) where gm1 and gm2 represent gain of said transconductance amplifiers, and R1 C1 s and R2 represent biasing and feedback resistors and capacitance. ### Claim 18 (depends on 11) The apparatus as recited in claim 11 includes a voltage offset resistor bias coupled between said write pole and a system ground potential. ### Claim 19 (depends on 11) The apparatus as recited in claim 11 includes an independent STO bias potential coupled by an independent STO pad connected to said write pole. ### Claim 20 A system for implementing an integrated spin-torque oscillator (STO) with an interface bias control for hard disk drives comprising: at least one disk; said disk including a disk media for storing data; a slider including a read transducer and a write transducer; said write transducer including a write pole and a write return pole; the spin-torque oscillator (STO) integrated with said slider for microwave assisted magnetic recording (MAMR); STO bias circuitry coupled to said slider and controlling a bias potential applied to said write return pole with respect to a disk media with said integrated STO bias circuitry. ### Claim 21 (depends on 20) The system as recited in claim 20 includes a spin-torque oscillator (STO) element coupled between said write pole and said write return pole. ### Claim 22 (depends on 20) The system as recited in claim 20 includes a Read/Write integrated circuit (IC) implementing said integrated STO bias circuitry.