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US 10,381,036 B1Granted
Laser bias calibration
AssigneeSeagate Technology LLC
InventorsTodd Michael Lammers, Abdelkrim Tatah, Tim Rausch, Robert Matousek
Life of this patent
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Abstract
Systems and methods of laser bias calibration are presented. A preamplifier circuit may include a laser voltage monitor circuit and a laser bias control circuit configured to automatically adjust an output laser bias threshold voltage based on a monitored laser voltage. The laser bias control circuit may include a first differentiator circuit, a second differentiator circuit, and a threshold detection circuit. The preamplifier circuit may be utilized in a heat assisted magnetic recording device.
Claims16
A device comprising:
- a heat-assisted magnetic recording (HAMR) data storage device having:
- a disc data storage medium having data tracks to store data;
- a laser emitter configured to heat the data tracks during write operations;
- a preamplifier circuit configured to determine a laser threshold current level to apply to the laser emitter based on a voltage of the laser emitter, including:
- an output to provide current to the laser emitter;
- a laser voltage monitor circuit configured to determine the voltage corresponding to the output;
- a first differentiator circuit configured to calculate a first derivative of the voltage;
- a second differentiator circuit configured to calculate a second derivative of the voltage based on the first derivative;
- a laser bias control circuit configured to determine the laser threshold current level for the output based on the second derivative and apply the laser threshold current level to the output of the laser emitter;
- and
- the laser bias control circuit including a threshold detector circuit configured to determine when the second derivative of the voltage reaches a threshold and update the laser threshold current level based on a bias current value corresponding to when the threshold was met.
8 more elements
A circuit comprising:
- a preamplifier for a heat-assisted magnetic recording (HAMR) data storage device, the preamplifier configured to determine a laser bias current level to apply to a laser emitter based on a voltage of the laser emitter and including:
- an output to provide current to a laser emitter to heat tracks of a disc data storage medium during write operations;
- a laser voltage monitor circuit configured to determine a voltage corresponding to the output;
- a first differentiator circuit configured to calculate a first derivative of the voltage;
- a second differentiator circuit configured to calculate a second derivative of the voltage based on the first derivative;
- and
- a threshold detector circuit configured to determine a laser bias current level for the output based on the second derivative reaching a threshold, and configured to apply the laser bias current level to the output.
4 more elements
A method comprising:
- determining a laser bias current threshold value to apply to a laser emitter of a heat-assisted magnetic recording (HAMR) data storage device based on a laser voltage of the laser emitter, in which the laser emitter is configured to heat tracks of a disc data storage medium during write operations, including:
- varying a bias current of the laser emitter over a range of currents;
- detecting the laser voltage corresponding to the bias current;
- determining the laser bias current threshold value based on the laser voltage;
- applying the laser bias current threshold value to the laser emitter;
- determining the laser bias current threshold value includes:
- calculating a first derivative of the laser voltage via a first differentiator circuit;
- calculating a second derivative of the laser voltage via a second differentiator circuit;
- comparing the second derivative to a threshold;
- and
- sampling the laser bias current when the second derivative reaches the threshold to obtain the laser bias current threshold value.
8 more elements
Dependencies are inferred from the claim text.