SE97TP datasheet(11/54 Pages) NXP

11 / 54 page

SE97_5

Product data sheet

Rev. 05 — 6 August 2009

11 of 54

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

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