IS43LD16640C datasheet(11/142 Pages) ISSI

11 / 142 page

IS43/46LD16640C

IS43/46LD32320C

Integrated Silicon Solution, Inc. — www.issi.com

Rev. C

07/02/2021

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Power-Off Sequence

Use the following sequence to power off the device. Unless specified otherwise, this procedure is mandatory and

applies to S4 devices.

While powering off, CKE must be held LOW (≤ 0.2 × VDDCA); all other inputs must be between VILmin and VIHmax.

The device outputs remain at High-Z while CKE is held LOW.

DQ, DM, DQS, and DQS# voltage levels must be between VSSQ and VDDQ during the power-off sequence to avoid

latch-up. CK, CK#, CS#, and CA input levels must be between VSSCA and VDDCA during the power-off sequence to

avoid latch-up.

Tx is the point where any power supply drops below the minimum value specified in the DC operating condition table.

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

Required Power Supply Conditions Between Tx and Tz:

• VDD1 must be greater than VDD2 - 200mV

• VDD1 must be greater than VDDCA - 200mV

• VDD1 must be greater than VDDQ - 200mV

• VREF must always be less than all other supply voltages

The voltage difference between VSS, VSSQ, and VSSCA must not exceed 100mV.

For supply and reference voltage operating conditions, see Recommended DC Operating Conditions table.

Uncontrolled Power-Off Sequence

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

1.At Tx, when the power supply drops below the minimum values specified, all power supplies must be turned off and

all power-supply current capacity must be at zero, except for any static charge remaining in the system.

2.After Tz , the device must power off. The time between Tx and Tz must not exceed 20ms. During this period, the

relative voltage between power supplies is uncontrolled. VDD1 and VDD2 must decrease 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

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.

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