SE97TP datasheet(36/55 Pages) NXP

36 / 55 page

SE97_7

Product data sheet

Rev. 07 — 29 January 2010

36 of 55

NXP Semiconductors

SE97

DDR memory module temp sensor with integrated SPD, 3.3 V

9.1 SE97 in memory module application

Figure 25 shows the SE97 being placed in the memory module application. The SE97 is

centered in the memory module to monitor the temperature of the DRAM and also to

provide a 2-kbit EEPROM as the Serial Presence Detect (SPD). In the event of

overheating, the SE97 triggers the EVENT output and the memory controller throttles the

memory bus to slow the DRAM. The memory controller can also read the SE97 and watch

the DRAM thermal behavior, taking preventive measures when necessary.

9.2 Layout consideration

The SE97 does not require any additional components other than the host controller to

read its temperature. It is recommended that a 0.1

μF bypass capacitor between the V

and VSS pins is located as close as possible to the power and ground pins for noise

protection.

9.3 Thermal considerations

In general, self-heating is the result of power consumption and not a concern, especially

with the SE97, which consumes very low power. In the event the SDA and EVENT pins

are heavily loaded with small pull-up resistor values, self-heating affects temperature

accuracy by approximately 0.5

°C.

Equation 1 is the formula to calculate the effect of self-heating:

(1)

where:

ΔT = T

j − Tamb

Tj = junction temperature

Tamb = ambient temperature

Rth(j-a) = package thermal resistance

VDD = supply voltage

IDD(AV) = average supply current

Fig 25. System application

002aac800

SE97

EVENT

DIMM

DRAM

MEMORY CONTROLLER

SMBus

CPU

ΔTR

th j-a

()

DD AV

()

OL SDA

()

sin

() SDA

()

OL EVENT

()

sin

()EVENT

()

[

]

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