Rainbow Electronics LM88 - Manual

LM88
Factory Programmable Dual Remote-Diode Thermostat
General Description
The LM88 is a dual remote-diode temperature sensor with 3
digital comparators. The LM88 has 3 open-drain outputs
(O_SP0, O_SP1 and O_CRIT) that can be used as inter-
rupts or to signal system shutdown. The digital comparators
can be factory programmed to make a greater than or less
than comparison. When programmed for a greater than
comparison outputs:
O_SP0 and O_SP1 activate when the temperatures mea-
sured by D0 or D1 exceed the associated setpoints of
T_SP0 or T_SP1.
O_CRIT activates when the temperature measured by
either D0 or D1 exceeds setpoint T_CRIT.
T_CRIT can be set at 1˚C intervals from −40˚C to +125˚C.
T_SP0 and T_SP1 can be set at 4˚C intervals in the range of
T_CRIT +127˚C/−128˚C. Hysteresis for all comparators is
set to 1˚C. O_CRIT, in conjunction with T_CRIT, could be
used to prevent catastrophic damage to key subsystems
such as notebook Card Bus cards while O_SP0 and O_SP1,
in conjunction with T_SP0 and T_SP1, can warn of an
impending failure.
The LM88 is available in an 8-lead mini-small-outline pack-
age.
Applications
n Microprocessor Thermal Management
n Appliances
n Portable Battery Powered Systems
n Fan Control
n Industrial Process Control
n HVAC Systems
n Remote Temperature Sensing
n Electronic System Protection
Features
n 2 external remote diode input channels
n 3 digital comparator outputs, 1 per remote diode and
one T_CRIT common to both
n Factory programmable greater than or less than
comparisons
n 1˚C comparator hysteresis
n 2 setpoints, T_SP0 and T_SP1, factory programmable in
4˚C intervals
n 1 setpoint, T_CRIT, factory programmable in 1˚C
intervals
n Active Low open-drain digital outputs
n 8-pin mini-SO plastic package
Key Specifications
j Power Supply Voltage 2.8V–3.8V
j Power Supply Current 1.5 mA (max)
j LM88 Temperature Range −40˚C to +85˚C
j Diode Setpoint Temperature
Range 0˚C to +125˚C
j Temperature Trip Point Accuracy:
Diode Junction
Temperature
(T
DJ
)
LM88CIM
Accuracy
LM88CIM
Temperature
Range
+45˚C to +85˚C ± 3˚C (max) −40˚C to +85˚C
+60˚C to +100˚C ± 3˚C (max) −40˚C to +85˚C
Note: These are sample ranges. Contact factory for other
ranges.
Simplified Block Diagram and Connection Diagram
MSOP-8/MUA08A Package
10132601
Top View
10132602
For simplicity, the effects of the hysteresis are not shown in the
temperature response diagram.
August 2001
LM88
Factory
Programmable
Dual
Remote-Diode
Thermostat
© 2001 National Semiconductor Corporation DS101326 www.national.com