EDJ1108BABG, EDJ1116BABG
Input Clock Frequency Change during Precharge Power-Down
Once the DDR3 SDRAM is initialized, the DDR3 SDRAM requires the clock to be “stable” during almost all states of
normal operation. This means once the clock frequency has been set and is to be in the “stable state”, the clock
period is not allowed to deviate except for what is allowed for by the clock jitter and SSC (Spread Spectrum
Clocking) specifications.
The input clock frequency can be changed from one stable clock rate to another stable clock rate under two
conditions: (1) self-refresh mode and (2) precharge power-down mode. Outside of these two modes, it is illegal to
change the clock frequency. For the first condition, once the DDR3 SDRAM has been successfully placed in to Self-
Refresh mode and tCKSRE has been satisfied, the state of the clock becomes a don’t care. Once a don’t care,
changing the clock frequency is permissible, provided the new clock frequency is stable prior to tCKSRX. When
entering and exiting Self-Refresh mode for the sole purpose of changing the clock frequency, the self-refresh entry
and exit specifications must still be met as outlined in Self-Refresh section.
The second condition is when the DDR3 SDRAM is in Precharge Power-down mode (either fast exit mode or slow
exit mode.) ODT must be at a logic low ensuring RTT is in an off state prior to entering Precharge Power-down mode
and CKE must be at a logic low. A minimum of tCKSRE must occur after CKE goes low before the clock frequency
may change. The DDR3 SDRAM input clock frequency is allowed to change only within the minimum and maximum
operating frequency specified for the particular speed grade. During the input clock frequency change, ODT and
CKE must be held at stable low levels. Once the input clock frequency is changed, stable new clocks must be
provided to the DRAM tCKSRX before Precharge Power-down may be exited; after Precharge Power-down is exited
and tXP has expired, the DLL must be RESET via MRS. Depending on the new clock frequency additional MRS
commands may need to be issued to appropriately set the WR, CL, and CWL with CKE continuously registered high.
During DLL relock period, ODT must remain low. After the DLL lock time, the DRAM is ready to operate with new
clock frequency. This process is depicted in the figure Clock Frequency Change in Precharge Power-Down Mode.
Previous clock frequency
New clock frequency
T0
T1
tIS
T2
Ta
Tb
Tc
Tc+1 Td
Td+1
Te
Te+1
/CK
CK
tIH
tCKSRE
tCKSRX
CKE
tCPDED
NOP
NOP
NOP
NOP
NOP
Command
Address
MRS
NOP
Valid
Valid
DLL
RESET
tXP
tAOFPD/tAOF
ODT
tDLLK
High-Z
High-Z
DQS, /DQS
DQ
DM
Enter precharge
power-down mode
Exit precharge
power-down mode
Frequency
change
Notes: 1. Applicable for both slow exit and fast exit precharge power-down.
2. tCKSRE and tCKSRX are self-refresh mode specifications but the values
they represent are applicable here.
3. tAOFPD and tAOF must be satisfied and outputs high-z prior to T1;
refer to ODT timing for exact requirements.
Clock Frequency Change in Precharge Power-Down Mode
Data Sheet E1248E40 (Ver. 4.0)
129
ELPIDA [ ELPIDA MEMORY ]
