SE97 Datasheet, PDF (35/54 Pages) NXP Semiconductors – DDR memory module temp sensor with integrated SPD, 3.3 V

NXP Semiconductors
SE97
DDR memory module temp sensor with integrated SPD, 3.3 V
9.1 SE97 in memory module application
Figure 24 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.
DIMM
DRAM
DRAM
SE97
DRAM
DRAM
SMBus
MEMORY CONTROLLER
Fig 24. System application
EVENT
CPU
002aac800
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_DD
and V_SS 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:
∆T = R_{th( j-a)} ×
(1)
[(V _DD × I _{DD( AV )}) + (V _OL(SDA) × I _{OL( sink)(SDA)}) + (V _{OL(EVENT )} × I _{OL( sink)EVENT} )]
where:
∆T = T_j − T_amb
T_j = junction temperature
T_amb = ambient temperature
R_th(j-a) = package thermal resistance
V_DD = supply voltage
I_DD(AV) = average supply current
SE97_5
Product data sheet
Rev. 05 — 6 August 2009
© NXP B.V. 2009. All rights reserved.
35 of 54