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"False write" protection AE

IP.com Disclosure Number: IPCOM000010617D
Original Publication Date: 2002-Dec-25
Included in the Prior Art Database: 2002-Dec-25
Document File: 2 page(s) / 18K

Publishing Venue

IBM

Abstract

HDD (Hard Disk Drive) must be designed to save the user data even if when the power suddenly shuts down. So the electrical components used in HDD is designed to manage this situation individually. However the user data destruction sometimes happen because of the mismatch of components. This shows the method to save the user data in any power-off situation by improving AE (Pre-Amplifier).

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THIS COPY WAS MADE FROM AN INTERNAL IBM DOCUMENT AND NOT FROM THE PUBLISHED BOOK

JP820020757 Akihiko Nadaguchi/Japan/IBM Yumi 1 Nagano, Masashi Murai

"False write" protection AE

   HDD needs the 12V/5V DC power and has 4 electrical components, HDC, R/W channel, Motor driver and AE. These components have "Low voltage sensor (LVS)" to stop the each operation safely when the power shuts down. But if there is the mismatch between each LVS threshold levels, HDD can enter the write mode and false write happen at power-off. For example, Fig.1 shows the mismatch between AE threshold level and Motor driver threshold level.

( Fig.1 )

AE has the logic signal called "-Write Gate (-WG)" which controls the read/write operation in HDD. When the -WG is "low" ( < 1.5V), HDD is in the "Write mode "and when the -WG is "high" ( > 1.5V) , HDD is in the read mode.

AE LVS threshold level is about 4V. On the other hand, the that of Motor driver is slightly higher. In this case, when the power shuts down, firstly the Motor driver LVS works and stops the operation and tells HDC that the power goes down. As soon as HDC receives this error signal, HDC makes all logic signal level 3.3V. So, the -WG which is AE logic signal goes 3.3V. Since the Motor driver is stopped, 3.3V becomes down as well as 5V. But if this Motor driver is switching regulator type, 3.3V rapidly down. As a result, the term in which HDD can write comes as Fig.1 and this false write erases the user data.

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