Seagate Technology Incorporated

Djunaedy Chandra Ang

KianKeong Ooi

WingKong Chiang

MingZhong Ding

BengWee Quak

JackMing Teng

Liang Shen

BaoHong Liu

A motor control circuit for controlling rotation of a motor includes parallel first and second controller paths (gears). Each path includes a proportional and integral (PI) controller and a digital to analog converter (DAC). The DACs operate over different dynamic ranges (gains). The respective PI controllers have different control parameters to provide a common frequency response. The first controller path is used to output motor control signals to control the application of drive current to the motor. The circuit switches to the second controller path once the first controller path operates within a selected tolerance of a minimum or maximum level of the first dynamic range. The final state of the first PI controller is used to configure the initial state of the second PI controller to eliminate transients. The use of different gears allows the circuit to adaptively accommodate large variations in motor current and spindle motor configurations.

Motor control circuit with adaptive controller path selection for different load conditions

An apparatus and method for writing a product information code (PIC) to a head-disc assembly (HDA) of a disc drive data handling system to facilitate subsequent identification of the HDA. The PIC is configured as a sequence of n multi-bit encoded words. Servo data are written to a disc of the HDA as a number of p angularly spaced apart servo data fields, the servo data used by a servo control circuit to effect head positional control. The n encoded words are distributed across a subset n of the p servo data fields so that the n encoded words replace at least a portion of the servo data in the n servo data fields. Preferably, the n encoded words are written to Gray code (track address) fields of the n servo data fields and are provided with error detection and correction capabilities.

Head-disc assembly with embedded product identification code

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Singapore, Singapore

Djunaedy Chandra Ang