SE98 Datasheet, PDF (10/39 Pages) NXP Semiconductors – DDR memory module temp sensor, 3.3 V

NXP Semiconductors
SE98
DDR memory module temp sensor, 3.3 V
– Competitor devices: If the EVENT output is not cleared before or when the
temperature is in the critical temperature threshold, EVENT will remain asserted
after the temperature drops below the critical temperature until a Clear EVENT
command.
– Work-around: Always clear the EVENT output before temperature exceeds the
critical temperature.
– SE98B will keep EVENT asserted after the temperature drops below the critical
temperature until a Clear EVENT command de-asserts EVENT.
7.4 Conversion rate
The conversion time is the amount of time required for the ADC to complete a temperature
measurement for the local temperature sensor. The conversion rate is the inverse of the
conversion period which describes the number of cycles the temperature measurement
completes in one second—the faster the conversion rate, the faster the temperature
reading is updated. The SE98’s conversion rate is at least 8 Hz or 125 ms.
7.5 Power-up default condition
After power-on, the SE98 is initialized to the following default condition:
• Starts monitoring local sensor
• EVENT register is cleared—EVENT output is pulled HIGH by external pull-ups
• EVENT hysteresis is defaulted to 0 °C
• Command pointer is defaulted to ‘00h’
• Critical Temp, Alarm Temperature Upper and Lower Boundary Trip register are
defaulted to 0 °C
• Capability register is defaulted to ‘0015h’
• Operational mode: comparator
• SMBus register is defaulted to ‘00h’
7.6 Device initialization
SE98 temperature sensors have programmable registers, which, upon power-up, default
to zero. The open-drain EVENT output is default to being disabled, comparator mode and
active LOW. The alarm trigger registers default to being unprotected. The configuration
registers, upper and lower alarm boundary registers and critical temperature window are
defaulted to zero and need to be programmed to the desired values. SMBus TIMEOUT
feature defaults to being enabled and can be programmed to disable. These registers are
required to be initialized before the device can properly function. Except for the SPD,
which does not have any programmable registers, and does not need to be initialized.
Table 4 shows the default values and the example value to be programmed to these
registers.
SE98_4
Product data sheet
Rev. 04 — 2 February 2009
© NXP B.V. 2009. All rights reserved.
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