4.7 Servo Control

d)During phase switching, the spindle motor starts rotating in low speed, and generates a counter electromotive force. The SVC detects this counter electromotive force and reports to the MPU using a PHASE signal for speed detection.

e)The MPU is waiting for a PHASE signal. When no phase signal is sent for a sepcific period, the MPU resets the SVC and starts from the beginning. When a PHASE signal is sent, the SVC enters the acceleration mode.

(2) Acceleration mode

In this mode, the MPU stops to send the phase switching signal to the SVC. The SVC starts a phase switching by itself based on the counter electromotive force. Then, rotation of the spindle motor accelerates. The MPU calcurates a rotational speed of the spindle motor based on the PHASE signal from the SVC, and accelerates till the rotational speed reaches 4,000 rpm. When the rotational speed reaches 4,000 rpm, the SVC enters the stable rotation mode.

(3) Stable rotation mode

The MPU calcurates a time for one revolution of the spindle motor based on the PHASE signal from the SVC. The MPU takes a difference between the current time and a time for one revolution at 4,000 rpm that the MPU already recognized. Then, the MPU keeps the rotational speed to 4,000 rpm by charging or discharging the charge pump for the different time. For example, when the actual rotational speed is 3,800 rpm, the time for one revolution is 15.789 ms. And, the time for one revolution at 4,000 rpm is 15 ms. Therefore, the MPU charges the charge pump for 0.789 ms × k (k: constant value). This makes the flowed current into the motor higher and the rotational speed up. When the actual rotational speed is faster than 4,000 rpm, the MPU discharges the pump the other way. This control (charging/discharging) is performed every 1 revolution.

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Fujitsu MHC2040AT, MHC2032AT, MHD2021AT, MHD2032AT manual Servo Control
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MHC2040AT, MHC2032AT, MHD2032AT, MHD2021AT specifications

Fujitsu offers a range of advanced hard disk drives (HDD) designed for various computing needs, including the MHD2021AT, MHD2032AT, MHC2032AT, and MHC2040AT models. These drives combine reliable performance, capacity options, and technological features aimed at enhancing data storage efficiency.

The Fujitsu MHD2021AT is known for its capacity of 20 GB, making it an excellent choice for users requiring a compact and efficient HDD. With a spindle speed of 5400 RPM, it balances speed and power consumption, catering to mobile computing and lower power devices. Its ATA interface ensures compatibility with a wide range of systems, making it a versatile option for various applications.

The MHD2032AT model offers a slightly higher capacity of 30 GB, maintaining similar technological attributes to its predecessor. With an enhanced data transfer rate, it allows for quicker access to stored files, perfect for users handling larger volumes of data. The robust error correction features in this model further ensure data integrity, making it a reliable choice for demanding environments.

For users needing more robust storage solutions, the MHC2032AT steps it up with features tailored for performance-heavy applications. Its 30 GB capacity is suited for desktop and workstation environments that require swift data retrieval and significant storage. The drive employs advanced caching techniques, which boost performance further by optimizing read and write operations, ensuring smoother multitasking capabilities.

The MHC2040AT is the flagship model in this line, providing an impressive storage capacity of 40 GB. This HDD is designed for high-performance applications where speed is crucial. The drive’s increased spindle speed and superior data transfer rates make it ideal for video editing, gaming, and large database management. Alongside its enhanced performance features, it includes advanced thermal management technology that maintains optimal operational temperatures, prolonging the drive's lifespan.

All four models leverage Fujitsu's commitment to data reliability, featuring robust shock resistance and low noise levels. Collectively, these drives cater to a spectrum of user needs, from compact data storage to high-capacity solutions, maintaining Fujitsu's reputation for quality and innovation in the storage market.
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