se98a NXP Semiconductors, se98a Datasheet - Page 27

• Manufacturer Part Number: se98a
• Description: Ddr Memory Module Temp Sensor, 1.7 V To 3.6 V
• Manufacturer: NXP Semiconductors

NXP Semiconductors
SE98A_1
Product data sheet
9.1 SE98A in memory module application
9.2 Layout consideration
9.3 Thermal considerations
Figure 15
The SE98A is centered in the memory module to provide the function to monitor the
temperature of the DRAM. In the event of overheat, the SE98A triggers the EVENT output
and the memory controller can throttle the memory bus to slow the DRAM, or the CPU
can increase the refresh rate for the DRAM. The memory controller can also read the
SE98A and watch the DRAM thermal behavior.
The SE98A does not require any additional components other than the host controller to
measure temperature. A 0.1 F bypass capacitor between the V
located as close as possible to the power and ground pins for noise protection.
In general, self-heating is the result of power consumption and not a concern, especially
with the SE98A, 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
where:
T
Fig 15. System application
T = T
T
T
R
V
V
I
I
OL1
OL2
j
amb
OL1
OL2
th(j-a)
=
= junction temperature
R
= SDA output current LOW
= EVENT output current LOW.
= ambient temperature
= SDA output low voltage
= EVENT output low voltage
th j-a
j
= package thermal resistance
shows the SE98A being placed in the memory module application with the SPD.
is the formula to calculate the effect of self-heating:
T
amb
DIMM
DRAM
V
DD
Rev. 01 — 5 March 2009
MEMORY CONTROLLER
I
DD
DRAM
+
SMBus
V
SDA
OL1
DDR memory module temp sensor, 1.7 V to 3.6 V
I
OL1
SCL
SE98A
SPD
+
V
OL2
EVENT
I
DRAM
OL2
DD
and V
DRAM
CPU
002aad760
© NXP B.V. 2009. All rights reserved.
SS
SE98A
pins is
27 of 42
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