Serial_DRAM_nonvolatizer

Published:2009/7/24 11:51:00 Author:Jessie | From:SeekIC

This circuit shows a DS1262 Serial DRAM nonvolatizer chip that is used to enable read/write access of DRAM from a simple 3-wire serial port. Refresh and RAS/CAS timing for the DRAM are performed automatically, transparent to operation of the serial port. In addition, the DS1262 performs all power switching and refresh duties that are necessary to retain DRAM data when the primary power supply fails. The backup supply input accepts a wide voltage range, suitable for use with rechargeable batteries. The DS1262 also provides an electronic gas gauge that can predict the condition of the backup supply. When the VCC1 power begins to drop, an internal circuit senses the changes, and the data-retention mode begins. The VCC1 input is then disconnected from the VCC0 output and the backup supply connected to the BKUP pin is switched in. The DS1262 also monitors the backup supply condition. If the backup supply is below VCC1, the backup-condition output pinBC is driven active low, and remains in this state until the backup supply voltage is restored to a level above VCC1. Dallas Semiconductors, Product Data Book, 1992/1993, p. 9-59.



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