SE97 Datasheet, PDF (11/54 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
– Work-around: Always clear the EVENT output before temperature exceeds the
critical temperature.
– SE97B 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 SE97’s conversion rate is at least 8 Hz or 125 ms.
7.4.1 What temperature is read when conversion is in progress
The SE97 has been designed to ensure a valid temperature is always available. When a
read to the temperature register is initiated through the SMBus, the device checks to see if
the temperature conversion process (Analog-to-Digital conversion) is complete and a new
temperature is available:
• If the temperature conversion process is complete, then the new temperature value is
sent out on the SMBus.
• If the temperature conversion process in not complete, then the previous temperature
value is sent out on the SMBus.
It is possible that while SMBus Master is reading the temperature register, a new
temperature conversion completes. However, this will not affect the data (MSB or LSB)
that is being shifted out. On the next read of the temperature register, the new
temperature value will be shifted out.
7.5 Power-up default condition
After power-on, the SE97 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 ‘0017h’ for the B grade
• Operational mode: comparator
• SMBus register is defaulted to ‘00h’
7.6 Device initialization
SE97 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
SE97_5
Product data sheet
Rev. 05 — 6 August 2009
© NXP B.V. 2009. All rights reserved.
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