1. General description
The NXP Semiconductors SE97 measures temperature from −40 °C to +125 °C with
JEDEC Grade B ±1 °C accuracy between +75 °C and +95 °C and also provide 256 bytes
of EEPROM memory communicating via the I
2
C-bus/SMBus. It is typically mounted on a
Dual In-line Memory Module (DIMM) measuring the DRAM temperature in accordance
with the new JEDEC (JC-42.4) Mobile Platform Memory Module Temperature Sensor
Component specification and also replacing the Serial Presence Detect (SPD) which is
used to store memory module and vendor information.
The SE97 thermal sensor operates over the V
DD
range of 3.0 V to 3.6 V and the EEPROM
over the range of 3.0 V to 3.6 V write and 1.7 V to 3.6 V read.
Placing the Temp Sensor (TS) on a DIMM allows accurate monitoring of the DIMM module
temperature to better estimate the DRAM case temperature (T
case
) to prevent it from
exceeding the maximum operating temperature of 85 °C. The chip set throttles the
memory traffic based on the actual temperatures instead of the calculated worst-case
temperature or the ambient temperature using a temp sensor mounted on the
motherboard. There is up to 30 % improvement in thin and light notebooks that are using
one or two 1 GB SO-DIMM modules. The TS is required on DDR3 RDIMM and RDIMM
ECC. Future uses of the TS will include more dynamic control over thermal throttling, the
ability to use the Alarm Window to create multiple temperature zones for dynamic
throttling and to save processor time by scaling the memory refresh rate.
The TS consists of a ΔΣ Analog-to-Digital Converter (ADC) that monitors and updates its
own temperature readings 10 times per second, converts the reading to a digital data, and
latches them into the data temperature register. User-programmable registers, the
specification of upper/lower alarm and critical temperature trip points, EVENT
output
control, and temperature shutdown, provide flexibility for DIMM temperature-sensing
applications.
When the temperature changes beyond the specified boundary limits, the SE97 outputs
an EVENT
signal using an open-drain output that can be pulled up between 0.9 V and
3.6 V. The user has the option of setting the EVENT
output signal polarity as either an
active LOW or active HIGH comparator output for thermostat operation, or as a
temperature event interrupt output for microprocessor-based systems. The EVENT
output
can even be configured as a critical temperature output.
The EEPROM is designed specifically for DRAM DIMMs SPD. The lower 128 bytes
(address 00h to 7Fh) can be Permanent Write Protected (PWP) or Reversible Write
Protected (RWP) by software. This allows DRAM vendor and product information to be
stored and write protected. The upper 128 bytes (address 80h to FFh) are not write
protected and can be used for general purpose data storage.
SE97
DDR memory module temp sensor with integrated SPD, 3.3 V
Rev. 07 — 29 January 2010 Product data sheet
