EDBA164B4PK-1DITF-R datasheet(66/152 Pages) MICRON

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Table 49: REFRESH Command Scheduling Separation Requirements (Continued)

Symbol

Minimum

Delay From

Notes

tRRD

REFpb

ACTIVATE command to a different bank than REFpb

ACTIVATE

REFpb affecting an idle bank (different bank than activate)

ACTIVATE command to a different bank than the prior ACTIVATE com-

mand

Note:

1. A bank must be in the idle state before it is refreshed, so REFab is prohibited following

an ACTIVATE command. REFpb is supported only if it affects a bank that is in the idle

state.

REFRESH Requirements

1. Minimum Number of REFRESH Commands

Mobile LPDDR2 requires a minimum number, R, of REFRESH (REFab) commands with-

in any rolling refresh window (tREFW = 32 ms @ MR4[2:0] = 011 or TC ≤ 85˚C). For actual

values per density and the resulting average refresh interval (tREFI), see Refresh Re-

quirements.

For tREFW and tREFI refresh multipliers at different MR4 settings, see the MR4 Device

Temperature (MA[7:0] = 04h) table.

For devices supporting per-bank REFRESH, a REFab command can be replaced by a full

cycle of eight REFpb commands.

2. Burst REFRESH Limitation

To limit current consumption, a maximum of eight REFab commands can be issued in

any rolling tREFBW (tREFBW = 4 × 8 × tRFCab). This condition does not apply if REFpb

commands are used.

3. REFRESH Requirements and Self Refresh

If any time within a refresh window is spent in self refresh mode, the number of re-

quired REFRESH commands in that window is reduced to the following:

R´ = R - RU

tSRF

tREFI

Where RU represents the round-up function

= R - RU R ×

tSRF

tREFW

216-Ball and 220-Ball, Dual-Channel LPDDR2 SDRAM

REFRESH Command

09005aef85eb530a

216b_220b_2ch_2e0e_embedded_lpddr2.pdf – Rev. F 08 /16 EN

Micron Technology, Inc. reserves the right to change products or specifications without notice.

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