Disk-Drive Pulse Duration Control for Jitter Mitigation
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Solution Overview
Problem
Existing pulse duration control systems in magnetic disk-drive systems cause unacceptable jitter and bad eye patterns due to overshoot current pulses exceeding the duration of a single bit, leading to suboptimal data rates.
Innovation Solution
A pulse duration control system that generates rising-edge and falling-edge overshoot signals based on comparative ramp voltages, allowing for positive and negative overshoot current pulses with maximum durations greater than a single bit, but reset at opposite transitions to mitigate jitter, comprising a rise delay system, fall delay system, and comparator system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the overshoot current pulse duration is extended greater than a single bit duration, then data writing precision is improved, but jitter increases and eye patterns deteriorate
Solution Approach 1:
The pulse duration is made dynamic rather than static. The system uses separate rise delay and fall delay systems that dynamically adjust the overshoot pulse duration based on the transition direction (rising or falling edge) of the write data signal. This allows the pulse to be extended beyond a single bit duration when needed for writing precision while automatically resetting at opposite transitions to prevent excessive jitter accumulation.
Solution Approach 2:
The single overshoot pulse control is segmented into two independent control paths: one for rising-edge transitions and one for falling-edge transitions. Each path has its own delay system and comparator, allowing independent optimization of pulse duration for each transition type. This segmentation enables precise control where the pulse can be extended for precision while being reset at opposite transitions to maintain reliability.
2Manufacturing precision
If the overshoot current pulse duration is extended greater than a single bit duration, then data writing precision is improved, but data rate decreases
Solution Approach 1:
The system uses periodic reset action where the overshoot pulse is extended beyond a single bit duration but then reset at opposite transitions (rising or falling edges). This periodic extension and reset creates a rhythm that maintains precision during the extended pulse while allowing rapid transitions during reset phases, thereby preserving high data rates despite the occasional extended pulse duration.
3Duration of action of moving object
If delay of the write data input signal is implemented to extend pulse duration, then overshoot current duration is increased, but jitter and eye pattern quality deteriorate
Solution Approach 1:
The delay mechanism is segmented into separate rise delay and fall delay systems rather than using a single unified delay. Each delay system operates independently for its respective transition type, allowing precise control of pulse duration extension without the cumulative jitter effects that would result from a single delayed signal path affecting all transitions.
Solution Approach 2:
The delay is made dynamic and selective rather than static and universal. The rise delay system activates only for rising-edge transitions while the fall delay system activates only for falling-edge transitions. This dynamic selection allows the overshoot duration to be extended when needed while preventing delay-induced jitter from affecting all data transitions, thereby maintaining eye pattern quality.
Data Source
AI summary
One embodiment includes a pulse duration control system for a magnetic disk-drive system. A rise delay system generates first control voltages in response to a write data input signal changing between a first state and a second state. A fall delay system generates second control voltages in response to the write data input signal changing between the first and second states. A comparator system generates a rising-edge overshoot signal and a falling-edge overshoot signal based on a comparison of the first and second control voltages. The rising-edge overshoot signal can set a duration of a positive overshoot current pulse for a write current at a transition of the write data input signal from the first state to the second state, and the falling-edge overshoot signal can set a duration of a negative overshoot current pulse for the write current at a transition from the second state to the first state.