Datasheet

AS4C16M32MD1
Confidential 46 Rev. 1.0/July 2014
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 restarting 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