Datasheet

7.14 Clock Stop
Stopping a clock during idle periods is an effective method of reducing power consumption.
The LPDDR SDRAM supports clock stop under the following conditions:
• the last command (ACTIVE, READ, WRITE, PRECHARGE, AUTO REFRESH or MODE REGISTER SET) has executed to
completion, including any data-out during read bursts; the number of clock pulses per access command depends on the device’s
AC timing parameters and the clock frequency;
• the related timing conditions (tRCD, tWR, tRP, tRFC, tMRD) has been met;
• CKE is held High When all conditions have been met, the device is either in “idle state” or “row active state” and clock stop
mode may be entered with CK held Low and CK held High.
Clock stop mode is exited by restart
ing the clock. At least one NOP command has to be issued before the next access
command may be applied. Additional clock pulses might be required depending on the system characteristics.
Figure 39 shows clock stop mode entry and exit.
• Initially the device is in clock stop mode
• The clock is restarted with the rising edge of T0 and a NOP on the command inputs
• With T1 a valid access command is latched; this command is followed by NOP commands in order to allow for clock stop as
soon as this access command is completed
• Tn is the last clock pulse required by the access command latched with T1
• The clock can be stopped after Tn
Figure 39 — Clock Stop Mode Entry and Exit
AS4C16M16MD1
256Mb MOBILE DDR SDRAM
Confidential
- 43/56 -
Ver.1.1 Oct.2015