SE98 Datasheet, PDF (1/39 Pages) NXP Semiconductors – DDR memory module temp sensor, 3.3 V

SE98
DDR memory module temp sensor, 3.3 V
Rev. 04 — 2 February 2009
Product data sheet
1. General description
The NXP Semiconductors SE98 measures temperature from −40 °C to +125 °C
communicating via the I²C-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 Thermal Sensor Component specification.
Placing the Temp Sensor (TS) on 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 a 30 % improvement in thin and light notebooks that are
using one or two 1G SO-DIMM modules, although other memory modules such as in
server applications will also see an increase in system performance. 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 an Analog-to-Digital Converter (ADC) that monitors and updates its
own temperature readings 8 times per second, converts the reading to a digital data, and
latches them into the data temperature registers. User-programmable registers, such as
Shutdown or Low-power modes and the specification of temperature event and critical
output boundaries, provide flexibility for DIMM temperature-sensing applications.
When the temperature changes beyond the specified boundary limits, the SE98 outputs
an EVENT signal. 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 SE98 supports the industry-standard 2-wire I²C-bus/SMBus serial interface. The
SMBus TIMEOUT function is supported to prevent system lock-ups. Manufacturer and
Device ID registers provide the ability to confirm the identify of the device. Three address
pins allow up to eight devices to be controlled on a single bus. To maintain
interchangeability with the I²C-bus/SMBus interface the electrical specifications are
specified with the operating voltage of 3.0 V to 3.6 V.