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under Voltage Ramp and Initialization Sequence). The MRW RESET command can be

issued from the idle state. This command resets all mode registers to their default val-

ues. Only the NOP command is supported during tINIT4. After MRW RESET, boot tim-

ings must be observed until the device initialization sequence is complete and the de-

vice is in the idle state. Array data is undefined after the MRW RESET command has

completed. For MRW RESET timing, see Voltage Ramp and Initialization Sequence.

MRW ZQ Calibration Commands

The MRW command is used to initiate a ZQ calibration command that calibrates output

driver impedance across process, temperature, and voltage. LPDDR2-S4 devices sup-

port ZQ calibration. To achieve tighter tolerances, proper ZQ calibration must be per-

formed.

There are four ZQ calibration commands and related timings: tZQINIT, tZQRESET,

tZQCL, and tZQCS. tZQINIT is used for initialization calibration; tZQRESET is used for

resetting ZQ to the default output impedance; tZQCL is used for long calibration(s); and

tZQCS is used for short calibration(s). See the MR10 Calibration (MA[7:0] = 0Ah) table

for ZQ calibration command code definitions.

ZQINIT must be performed for LPDDR2 devices. ZQINIT provides an output impe-

dance accuracy of ±15%. After initialization, the ZQ calibration long (ZQCL) can be used

to recalibrate the system to an output impedance accuracy of ±15%. A ZQ calibration

short (ZQCS) can be used periodically to compensate for temperature and voltage drift

in the system.

ZQRESET resets the output impedance calibration to a default accuracy of ±30% across

process, voltage, and temperature. This command is used to ensure output impedance

accuracy to ±30% when ZQCS and ZQCL commands are not used.

One ZQCS command can effectively correct at least 1.5% (ZQ correction) of output im-

pedance errors within tZQCS for all speed bins if maximum sensitivities are met as

specified in Output Driver Sensitivity Definition and Output Driver Temperature and

Voltage Sensitivity. The appropriate interval between ZQCS commands can be deter-

mined using these tables and system-specific parameters.

Mobile LPDDR2 devices are subject to temperature drift rate (Tdriftrate) and voltage drift

rate (Vdriftrate) in various applications. To accommodate drift rates and calculate the

necessary interval between ZQCS commands, apply the following formula:

correction

sens × Tdriftrate) + (Vsens × Vdriftrate)

Where Tsens = MAX (dRONdT) and Vsens = MAX (dRONdV) define temperature and volt-

age sensitivities.

For example, if Tsens = 0.75%/˚C, Vsens = 0.20%/mV, Tdriftrate = 1˚C/sec, and Vdriftrate =

15 mV/sec, then the interval between ZQCS commands is calculated as:

1.5

(0.75 × 1) + (0.20 × 15)

= 0.4s

A ZQ calibration command can only be issued when the device is in the idle state with

all banks precharged.

No other activities can be performed on the data bus during calibration periods

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

MODE REGISTER WRITE 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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