| 摘要 |
Undershoot and overshoot control circuitry is provided in a write driver circuit to enhance its efficiency and ability to quickly change directions of write current through a write head. The undershoot and overshoot control circuitry includes: (1) an undershoot reduction circuit, which adds current to the write current when one head terminal has a voltage higher than the opposite head terminal and the input signals are in a certain state, indicating that the write current waveform is about to experience some level of undershoot; (2) an overshoot enhancement circuit, which adds current to the write current when one of the head terminals has a voltage lower than a predetermined threshold, indicating that the write current waveform is about to experience some level of overshoot; and (3) an overshoot reduction circuit, which provides a resistance between the head terminals in parallel with the write head to damp overshoot, when one of the head terminals has a voltage lower than a predetermined threshold, indicating that the write current waveform is about to experience some level of overshoot. The predetermined thresholds, the currents added to the write current, and the resistance provided are all programmable in one embodiment, so that the undershoot and overshoot of the write driver circuit may be precisely controlled for efficient operation.
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