IS43LD16640C datasheet(69/142 Pages) ISSI

69 / 142 page

IS43/46LD16640C

IS43/46LD32320C

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

Rev. C

07/02/2021

® Long-term Support

World Class Quality

Temperature Sensor

LPDDR2 devices feature a temperature sensor whose status can be read from MR4. This sen-

sor can be used to determine an appropriate refresh rate, determine whether AC timing derating is

required in the extended temperature range, and/or monitor the operating temperature. Either the

temperature sensor or the device operating temperature can be used to determine whether operat-

ing temperature requirements

are being met (see Operating Temperature Range table). Temperature sensor data can be read

from MR4 using the mode register read protocol.

Upon exiting self-refresh or power-down, the device temperature status bits will be no older than

tTSI.

When using the temperature sensor, the actual device case temperature may be higher than the

operating temperature specification that applies for the standard or extended temperature ranges

(see table noted above). For example, TCASE could be above 85˚C when MR4[2:0] equals 011b.

To ensure proper operation using the temperature sensor, applications must accommodate the

parameters in the temperature sensor definitions table.

Temperature Sensor Definitions and Operating Conditions

LPDDR2 devices accommodate the temperature margin between the point at which the device

temperature enters the extended temperature range and the point at which the controller reconfig-

ures the system accordingly. To determine the required MR4 polling frequency, the system must

use the maximum TempGradient and the maximum response time of the system according to the

following equation:

TempGradient × (ReadInterval + tTSI + SysRespDelay)

≤ 2°C

For example, if TempGradient is 10˚C/s and the SysRespDelay is 1ms:

10°C / s × (ReadInterval + 32ms + 1ms)

≤ 2°C

In this case, ReadInterval must not exceed 167ms

ParameterSymbolMax/MinValue

Unit

Notes

System Temperature Gradient TempGradient

MaxSystem Dependent C/s

Maximum temperature gradient

experienced by the memory device at the

temperature of interest over a range of 2°C.

MR4 Read Interval

ReadInterval

MaxSystem Dependent ms Time period between MR4 READs from the

system.

Temperature Sensor Interval tTSI

Max16ms Maximum delay between internal updates

of MR4.

System Response Delay

SysRespDela

MaxSystem Dependent ms Maximum response time from an MR4

READ to the system response.

Device Temperature Margin TempMargin

Max2

C Margin above maximum temperature to

support controller response.

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