Browse Prior Art Database

Utilization of Non-Volatile Memory System Battery to Maintain Independent Real Time Clock.

IP.com Disclosure Number: IPCOM000033267D
Original Publication Date: 2004-Dec-02
Included in the Prior Art Database: 2004-Dec-02
Document File: 1 page(s) / 322K

Publishing Venue

IBM

Abstract

In most modern storage systems there is a need for the system to have a concept of date and time that is associatable with the actual calendar and wall time of the users and other systems. To avoid having the user tell the system what the date and time is each time the system is powered on, it is now customary for the systems to have a clock/calendar integrated circuit (RTC or real-time-clock) that is powered from a battery to keep track of time during the periods of time when the system is powered off. In general, batteries are items that it is preferable to avoid in a system. They have limited life span and there are significant ecological concerns with thier composition which leads to the necessity of expensive recycling programs to prevent the battery cells from entering the waste stream. This invention provides power to the RTC in such a manner as to avoid adding an additional batteries or battery system to a midrange RAID controller. The current art is to add a separate battery for the RTC or have an external system set the time in the controller on each power on.

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Utilization of Non-Volatile Memory System Battery to Maintain Independent Real Time Clock.

Provide power directly to real time clock from the output of the non-voliatile memory battery pack befor any power switches. The battery for non-volitale memeories are normally diconnected from the load propr to expected shutdown to preserve battery capacity for use only for unexpected shutdowns. The RTC draws power from the batteries all the time, but its load is on the order of or less than the self-discharge power loss inheirent in the batteries themselves and thus does not appriciabbly add to the battery load.

Under conditions of extended unexpected power loss, the batteries will discharge to a fully discharged state. When fully discharged, the non-volatile battery controller will open the load switch preventing an over-disharged state (at the loss of the memory contents). The residual charge in batteries at full discharge is insufficient to hold the memory up for any approcaible period of time, but is more than adequate to power the realime clock for many more days without significantly overdischarging the batteries.

RSENSE

3.3V to BBU logic

3.3V to BBU logic

 Analog Regulator

 Analog Regulator

12V

12V

3.3V to BBU logic

3.3V to BBU logic

 Logic Regulator

 Logic Regulator

 DIMM Regulator

 DIMM Regulator

Backup Switch

Backup Switch

RSENSE

Real Time Clock

Real Time Clock

BBU Controller card

Midplane

BBU Controller card

Midplane

1

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