SE97TP datasheet(9/54 Pages) NXP

9 / 54 page

SE97_5

Product data sheet

Rev. 05 — 6 August 2009

9 of 54

NXP Semiconductors

SE97

DDR memory module temp sensor with integrated SPD, 3.3 V

7.3.2 EVENT thresholds

7.3.2.1

Alarm window

The device provides a comparison window with an UPPER trip point and a LOWER trip

point, programmed through the Upper Boundary Alarm Trip register (02h), and Lower

Boundary Alarm Trip register (03h). The Upper Boundary Alarm Trip register holds the

upper temperature trip point, while the Lower Boundary Alarm Trip register holds the lower

temperature trip point as modiﬁed by hysteresis as programmed in the Conﬁguration

above or below) the alarm window.

• Advisory note:

– NXP Device: The EVENT output can be cleared through the Clear EVENT bit

(CEVNT) or SMBus Alert.

– Competitor Device: The EVENT output can be cleared only through the

Clear EVENT bit (CEVNT).

– Work-around: Only clear EVENT output using the Clear EVENT bit (CEVNT).

– There will be no change to NXP devices.

The Upper Boundary Alarm Trip should always be set above the Lower Boundary Alarm

Trip.

• Advisory note:

– NXP device: Requires one conversion cycle (125 ms) after setting the alarm

window before comparing the alarm limit with temperature register to ensure that

there is correct data in the temperature register before comparing with the Alarm

Window and operating EVENT output.

– Competitor devices: Compares the alarm limit with temperature register at any

time, so they get the EVENT output immediately when new UPPER or LOWER

Alarm Windows and the EVENT output are set at the same time.

– Work-around: Wait at least 125 ms before enabling EVENT output (EOCTL = 1).

– SE97B will compare alarm window and temperature register immediately.

7.3.2.2

Critical trip

The Tth(crit) temperature setting is programmed in the Critical Alarm Trip register (04h) as

modiﬁed by hysteresis as programmed in the Conﬁguration register. When the

temperature reaches the critical temperature value in this register (and EVENT is

enabled), the EVENT output asserts and cannot be de-asserted until the temperature

drops below the critical temperature threshold. The Event cannot be cleared through the

Clear EVENT bit (CEVNT) or SMBus Alert.

The Critical Alarm Trip should always be set above the Upper Boundary Alarm Trip.

• Advisory note:

– NXP device: Requires one conversion cycle (125 ms) after setting the Alarm

Window before comparing the alarm limit with temperature register to ensure that

there is correct data in the temperature register before comparing with the Alarm

Window and operating EVENT output.

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