K4X56163PE Datasheet, PDF (22/48 Pages) Samsung semiconductor – 16M x16 Mobile DDR SDRAM

K4X56163PE-L(F)G
Mobile-DDR SDRAM
Auto Refresh & Self Refresh
Auto Refresh
An auto refresh command is issued by having CS, RAS and CAS held low with CKE and WE high at the rising edge of the clock(CK).
All banks must be precharged and idle for tRP(min) before the auto refresh command is applied. No control of the external address
pins is required once this cycle has started because of the internal address counter. When the refresh cycle has completed, all banks
will be in the idle state. A delay between the auto refresh command and the next activate command or subsequent auto refresh com-
mand must be greater than or equal to the tARFC(min).
CK
CK
Command PRE
CKE = High
Auto
Refresh
tRP
tARFC(min)
CMD
Figure.16 Auto refresh timing
Self Refresh
A Self Refresh command is defined by having CS, RAS, CAS and CKE held low with WE high at the rising edge of the clock. Once
the self Refresh command is initiated, CKE must be held low to keep the device in Self Refresh mode. After 1 clock cycle from the self
refresh command, all of the external control signals including system clock(CK, CK) can be disabled except CKE. The clock is inter-
nally disabled during Self Refresh operation to reduce power. To exit the Self Refresh mode, supply stable clock input before return-
ing CKE high, assert deselect or NOP command and then assert CKE high. In case that the system uses burst auto refresh during
normal opreation, it is recommended to use burst 8192 auto refresh cycle immediately before entering self refresh mode and after
exiting in self refresh mode. On the other hand, if the system uses the distributed auto refresh, the system only has to keep the
refresh duty cycle.
CK, CK
Command
CKE
Self
Refresh
tIS
Stable Clock
NOP
tIS
tSRFX(min)
Figure.17 Self refresh timing
Active
22
March 2004