LM87CIMT/NOPB National Semiconductor, LM87CIMT/NOPB Datasheet - Page 19

• Manufacturer Part Number: LM87CIMT/NOPB
• Description: IC INTERFACE SER MONITOR 24TSSOP
• Manufacturer: National Semiconductor
• Series: PowerWise®r

Specifications of LM87CIMT/NOPB

• Function: Hardware Monitor
• Topology: ADC (Sigma Delta), Comparator, Fan Speed Control, Register Bank
• Sensor Type: External & Internal
• Sensing Temperature: -40°C ~ 125°C, External Sensor
• Output Type: I²C™/SMBus™
• Output Alarm: No
• Output Fan: Yes
• Voltage - Supply: 2.8 V ~ 3.8 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 24-TSSOP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: *LM87CIMT; *LM87CIMT/NOPB; LM87CIMT

9.0 WATCHDOG LIMIT COMPARISONS AND INTERRUPT
STRUCTURE
Figure 10
LM87 can generate Interrupts as a result of each of its internal
WATCHDOG registers on the analog, temperature, and fan
inputs.
External Interrupts can come from the following sources.
While the label suggests a specific type or source of Interrupt,
this label is not a restriction of its usage, and it could come
from any desired source:
•
Chassis Intrusion: This is an active high interrupt from
any type of device that detects and captures chassis
intrusion violations. This could be accomplished
mechanically, optically, or electrically, and circuitry
external to the LM87 is expected to latch the event. The
design of the LM87 allows this input to go high even with
no power applied to the LM87, and no clamping or other
depicts the Interrupt Structure of the LM87. The
FIGURE 10. Interrupt Structure
19
•
interference with the line will occur. This line can also be
pulled low for at least 20 ms by the LM87 to reset a typical
Chassis Intrusion circuit. This reset is activated by setting
Bit 7 of CI Clear Register (46h) high. The bit in the Register
is self-clearing.
THERM# Input: This is an active low interrupt that would
typically be generated by an external temperature
monitoring system. If the THERM# output is currently
inactive and this input is pulled low by an external circuit,
the THERM# Interrupt Status bit will be set. In addition, the
DAC output will be forced to full scale operation while
THERM# is pulled low by the external source. This allows
a separate thermal sensor to override the current fan
speed setting in an overtemperature situation not sensed
by the LM87. The DAC setting will return to normal when
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