97SD3240_06 Datasheet, PDF (36/39 Pages) Maxwell Technologies – 1.25Gb SDRAM 8-Meg X 40-Bit X 4-Banks

1.25Gb (8-Meg X 40-Bit X 4-Banks) SDRAM
97SD3240
power-down mode, and command input is enabled from the next clock. In this mode, internal refresh is not
performed.
Clock suspend mode: By driving CKE to Low during a bank-active or read/write operation, the SDRAM
enters clock suspend mode. During clock suspend mode, external input signals are ignored and the internal
state is maintained. When CKE is driven High, the SDRAM terminates clock suspend mode, and command
input is enabled from the next clock. For more details, refer to the “CKE Truth Table”.
Power-up sequence: The SDRAM should use the following sequence during power-up:
The CLK, CKE, CS, DQM and DQ pins stay low until power stabilizes.
The CLK pin is stable within 100ms after power stabilizes before the following initialization sequence.
The CKE and DQM is driven high between when power stabilizes and the initialization sequence.
This SDRAM has V_CC clamp diodes for CLK, CKE, CS, DQM and DQ pins. If these pins go high before
power up, the large current flows from these pins to V_CC through the diodes.
Initialization sequence: When 200ms or more has past after the power up sequence, all banks must be
precharged using the precharge command (PALL). After t_RP delay, set 8 or more auto refresh commands
(REF). Set the mode register set command (MRS) to initialize the mode register. It is recommended that by
keeping DQM and CKE High, the output buffer becomes High-Z during initialization sequence, to avoid DQ
bus contention on a memory system formed with a number of devices.
05.10.06 Rev 4
All data sheets are subject to change without notice 36
©2006 Maxwell Technologies
All rights reserved.