MT42L256M32D4KP-3 IT:A【PDF 43/164 页】IC LPDDR2 SDRAM 8GBIT 168FBGA

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2Gb: x16, x32 Mobile LPDDR2 SDRAM S4

Mode Register Definition

Tx is the point where any power supply drops below the minimum value specified in

the Recommended DC Operating Conditions table.

Tz is the point where all power supplies are below 300mV. After Tz, the device is pow-

ered off.

Required Power Supply Conditions Between Tx and Tz:

V DD1 must be greater than V DD2 - 200mV

V DD1 must be greater than V DDCA - 200mV

V DD1 must be greater than V DDQ - 200mV

V REF must always be less than all other supply voltages

The voltage difference between V SS , V SSQ , and V SSCA must not exceed 100mV.

For supply and reference voltage operating conditions, see Recommended DC Operat-

ing Conditions table.

Uncontrolled Power-Off

When an uncontrolled power-off occurs, the following conditions must be met:

? At Tx, when the power supply drops below the minimum values specified in the Rec-

ommended DC Operating Conditions table, all power supplies must be turned off and

all power-supply current capacity must be at zero, except for any static charge re-

maining in the system.

? After Tz (the point at which all power supplies first reach 300mV), the device must

power off. The time between Tx and Tz must not exceed t POFF. During this period, the

relative voltage between power supplies is uncontrolled. V DD1 and V DD2 must de-

crease with a slope lower than 0.5 V/μs between Tx and Tz.

An uncontrolled power-off sequence can occur a maximum of 400 times over the life of

the device.

Table 9: Power-Off Timing

Parameter

Maximum power-off ramp time

Symbol

t POFF

Min

–

Max

Unit

sec

Mode Register Definition

LPDDR2 devices contain a set of mode registers used for programming device operating

parameters, reading device information and status, and for initiating special operations

such as DQ calibration, ZQ calibration, and device reset.

Mode Register Assignments and Definitions

The MRR command is used to read from a register. The MRW command is used to write

to a register. An “R” in the access column of the mode register assignment table indi-

cates read-only; a “W” indicates write-only; “R/W” indicates read or write capable or

enabled.

PDF: 09005aef83f3f2eb

2gb_mobile_lpddr2_s4_g69a.pdf – Rev. N 3/12 EN

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

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