Self-Servo Write Tune Feature for Preamps
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Solution Overview
Problem
In hard disk drives (HDDs), the mismatch between read/write heads can lead to variations in fly-height, causing errors during data operations due to temperature changes and differences in heating power requirements, which existing technologies fail to adequately compensate for.
Innovation Solution
A system and method using digital codewords to control waveform parameters of write current and heating power for each head, optimizing parameters such as overshoot pulse amplitude, duration, and DC value, and fly-height calibration to maintain consistent fly-height across multiple heads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If digital codewords are used to control waveform parameters for each head, then manufacturing precision of fly-height is improved, but device complexity increases
Solution Approach 1:
The patent applies local quality by assigning individualized waveform parameters (overshoot pulse amplitude, duration, DC value) to each head through unique digital codewords. This allows each head to have customized write current characteristics that compensate for its specific manufacturing variations, thereby achieving consistent fly-height across all heads despite individual differences.
Solution Approach 2:
The patent utilizes parameter changes by modifying waveform parameters (amplitude, duration, DC value) based on digital codewords stored in memory. The preamp selectively changes these parameters for each head during servo writing operations, enabling precise control of fly-height by adjusting the write current characteristics to match each head's specific requirements.
2Reliability
If head mismatch compensation is implemented, then reliability of data operations is improved, but ease of operation deteriorates
Solution Approach 1:
The patent implements self-service by automatically retrieving the appropriate digital codeword from memory based on head identification and applying the correct waveform parameters without requiring manual intervention. The system self-adjusts the write current characteristics for each head, compensating for mismatches automatically and maintaining high reliability while keeping operations simple.
Solution Approach 2:
The patent employs feedback mechanisms where the preamp controller automatically selects and applies the correct waveform parameters based on head-specific digital codewords. This closed-loop approach ensures that each head receives the optimal parameters for its characteristics, improving reliability while maintaining ease of operation through automated parameter selection.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach ensures uniform servo writing and maintains consistent fly-height, reducing errors and improving data operation reliability by compensating for head mismatches and temperature-induced variations.
Implementation Method 1
Each head 20 includes a write element, such as an inductor, that generates a magnetic field
Implementation Method 2
a read element, such as a magneto-resistive (MR) element, that senses the magnetic field on the platter 16
Implementation Method 3
When reading data, the magnetic fields stored on the magnetic surfaces of the platters 16 induce low-level analog signals in the read element of the head 20
Data Source
AI summary
A system includes N channels and a control module. Each of the N channels includes a latch and a signal generator module, where N is an integer greater than 1. The latch selectively latches a B-bit codeword, where B is an integer greater than 1. The signal generator module generates a signal based on the B bit codeword. The control module transmits the B-bit codeword via a B-bit data bus to the latch of each of the N channels. The control module generates control signals that select the latch in at least one of the N channels.