Disk Drive Preamplifier Common Signal Return Lead Crosstalk Reduction

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Solution Overview

Problem

In magnetic disk drives with multiple read transducers, existing designs face challenges in minimizing area, power consumption, and reducing electronic noise due to the need for multiple independent differential amplifiers and extensive electrical connections, which lead to skew and fly-height control issues.

Innovation Solution

A common signal return lead system is introduced, allowing a single-ended signal from each read transducer to be connected through a preamplifier with isolated differential amplifiers and separate power supply isolation elements, reducing the number of electrical paths and layout area, and utilizing a common-base amplifier configuration to minimize crosstalk and noise.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If multiple independent differential amplifiers are used for each read transducer, then signal amplification quality is improved, but layout area and device complexity increase

Engineering Contradiction:

Improvesignal amplification qualityVSAvoidlayout area

Core Design Contradiction:

Measurement precisionVSArea of stationary object

Solution Approach 1:

Multiple read transducer signals are combined into a single differential pair of traces. The patent merges N read transducer inputs into one differential amplifier, reducing the number of separate amplifiers and traces needed. This consolidation directly reduces layout area while maintaining signal amplification capability through the shared differential amplifier architecture.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

A single differential amplifier serves multiple read transducers simultaneously. The amplifier is designed to accept inputs from N different read transducers and process them through a common signal path. This multi-functional approach eliminates the need for dedicated amplifiers for each transducer, reducing overall device complexity and layout requirements.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Measurement precision

If multiple independent differential amplifiers are used for each read transducer, then signal processing capability is improved, but power consumption increases

Engineering Contradiction:

Improvesignal processing capabilityVSAvoidpower consumption

Core Design Contradiction:

Measurement precisionVSUse of energy by moving object

Solution Approach 1:

Multiple amplifier functions are merged into a single differential amplifier circuit. By combining N transducer signals into one amplifier, the total power consumption is reduced compared to having N separate amplifiers, while still providing adequate signal processing capability for all transducers through the shared amplification stage.

Inventive Principle:

Principle #5Merging (Combining)

3Measurement precision

If extensive electrical connections are made between read transducers and amplifiers, then signal integrity is improved, but skew and fly-height control issues worsen

Engineering Contradiction:

Improvesignal integrityVSAvoidskew and fly-height control

Core Design Contradiction:

Measurement precisionVSManufacturing precision

Solution Approach 1:

Multiple electrical connections are merged into a single differential pair of traces that carries combined signals from N read transducers. This reduction in the number of traces eliminates skew issues between multiple differential pairs and simplifies fly-height control, as fewer traces mean fewer sources of manufacturing variation and alignment complexity.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

Instead of having each transducer connect to its own dedicated amplifier through separate traces (one-to-one mapping), the patent inverts the approach by having multiple transducers share a common amplifier through a single differential pair (many-to-one mapping). This inversion fundamentally changes the connection topology to eliminate skew and simplify control.

Inventive Principle:

Principle #13The other way round (Inversion)

4Stability of the object's composition

If separate power supply lines are used for each amplifier, then power supply stability is improved, but device complexity and layout area increase

Engineering Contradiction:

Improvepower supply stabilityVSAvoiddevice complexity

Core Design Contradiction:

Stability of the object's compositionVSDevice complexity

Solution Approach 1:

Multiple power supply lines for separate amplifiers are merged into a single power supply configuration for the shared differential amplifier. This consolidation reduces device complexity and layout area while maintaining power supply stability through the unified power delivery to the common amplifier circuit.

Inventive Principle:

Principle #5Merging (Combining)

Data Source

PatentUS9218822B1Disk drive with preamplifier with isolation for multiple readers in a slider with a common return signal

Publication Date: 2015.12.22 WESTERN DIGITAL TECHNOLOGIES INC

AI summary

Interconnect and preamplifier designs are described for use in a disk drive with a common signal return lead system that interconnects a plurality of read transducers (readers) in a slider through the suspension to the preamplifier mounted on the actuator. Preamplifier embodiments have an isolated differential amplifier for each of the plurality of readers in the slider. The set of signal traces in the suspension include a common signal return lead for the plurality of readers in the slider. A preamplifier circuit design according to an embodiment of the invention includes isolated amplifiers for each reader with a separate bias source and power supply isolation elements for both power supply polarities for reduced crosstalk signal and noise between amplifiers.