SE98A Datasheet, PDF (10/43 Pages) NXP Semiconductors – DDR memory module temp sensor, 1.7 V to 3.6 V

NXP Semiconductors
SE98A
DDR memory module temp sensor, 1.7 V to 3.6 V
In interrupt mode, EVENT asserts when the temperature crosses the alarm upper
boundary. If the EVENT output is cleared and the temperature continues to increase until
it crosses the critical temperature threshold, EVENT asserts again. Because the
temperature is greater than the critical temperature threshold, a Clear EVENT command
does not clear the EVENT output. Once the temperature drops below the critical
temperature, EVENT de-asserts immediately.
• Advisory notification:
– NXP device: If the EVENT output is not cleared before the temperature goes above
the critical temperature threshold EVENT de-asserts immediately when
temperature drops below the critical temperature.
– 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 SE98A’s conversion rate is at least 8 Hz or 125 ms.
7.4.1 What temperature is read when conversion is in progress
The SE98A 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 the 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.
SE98A_2
Product data sheet
Rev. 02 — 6 August 2009
© NXP B.V. 2009. All rights reserved.
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