SE98 Datasheet, PDF (8/39 Pages) NXP Semiconductors – DDR memory module temp sensor, 3.3 V

NXP Semiconductors
SE98
DDR memory module temp sensor, 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
register. When enabled, the EVENT output triggers whenever entering or exiting (crossing
above or below) the alarm window.
• Advisory note:
– NXP Device: The EVENT output can be cleared through the Clear EVENT bit or
SMBus Alert.
– Competitor Device: The EVENT output can be cleared only through the Clear
EVENT bit.
– Work-around: Only clear EVENT output using the EVENT bit.
– There will be no change to the NXP device.
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
and Event B3 are set at the same time.
– Work-around: Wait at least 125 ms before enabling EVENT output.
– SE98B will compare alarm window and temperature register immediately after
setting.
7.3.2.2 Critical trip
The T_th(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 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.
SE98_4
Product data sheet
Rev. 04 — 2 February 2009
© NXP B.V. 2009. All rights reserved.
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