HYB25D256400BT Datasheet, PDF (45/77 Pages) Infineon Technologies AG – 256-Mbit Double Data Rate SDRAM, Die Rev. B

HYB25D256[400/800/160]B[T/C](L)
256-Mbit Double Data Rate SDRAM, Die Rev. B
Power-Down
Power-down is entered when CKE is registered LOW (no accesses can be in progress). If power-down
occurs when all banks are idle, this mode is referred to as precharge power-down; if power-down occurs
when there is a row active in any bank, this mode is referred to as active power-down. Entering power-down
deactivates the input and output buffers, excluding CK, CK and CKE. The DLL is still running in Power Down
mode, so for maximum power savings, the user has the option of disabling the DLL prior to entering Power-
down. In that case, the DLL must be enabled after exiting power-down, and 200 clock cycles must occur
before a Read command can be issued. In power-down mode, CKE Low and a stable clock signal must be
maintained at the inputs of the DDR SDRAM, and all other input signals are “Don’t Care”. However, power-
down duration is limited by the refresh requirements of the device, so in most applications, the self refresh
mode is preferred over the DLL-disabled power-down mode.
The power-down state is synchronously exited when CKE is registered HIGH (along with a Nop or Deselect
command). A valid, executable command may be applied one clock cycle later.
Power Down
CK
CK
CKE
Command
t_IS
VALID
No column
access in
progress
NOP
Enter Power Down mode
(Burst Read or Write operation
must not be in progress)
t_IS
NOP
Exit
power down
mode
VALID
Don’t Care
Page 45 of 77
2003-01-09, V1.1