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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

Power Supply Voltage 2.8V–3.8V

Power Supply Current 1.5 mA (max)

LM88 Temperature Range −40˚C to +85˚C

Diode Setpoint Temperature

Range 0˚C to +125˚C

Temperature Trip Point Accuracy:

Diode Junction

Temperature

)

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

Summary of content (9 pages)

PAGE 1
LM88 Factory Programmable Dual Remote-Diode Thermostat General Description Features 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 interrupts or to signal system shutdown. The digital comparators can be factory programmed to make a greater than or less than comparison.
PAGE 2
LM88 Simplified Block Diagram and Connection Diagram Order Number Device Marking NS Package Number Transport Media T08A MUA08A or MSOP-8 Tape and Real T08A MUA08A or MSOP-8 LM88CIMM-A LM88CIMMX-A LM88CIMM-B LM88CIMMX-B (Continued) T_SP0 (˚C) T_SP1 (˚C) T_CRIT (˚C) S etpoint Accuracy (˚C) 61 49 80 ±3 41 49 60 ±3 Rail Rail Tape and Real For other setpoints please contact the factory. Performance is dependent on temperature range. Typical Application 10132613 FIGURE 1.
PAGE 3
Operating Ratings(Note 1) (Note 1) Input Voltage 6V Input Current at any pin (Note 2) 5mA Package Input Current (Note 2) 20mA LM88 Absolute Maximum Ratings Operating Temperature Range TMIN ≤ T ≤ TMAX −40˚C ≤ TA ≤ +85˚C LM88CIMM 0˚C ≤ TDJ ≤ +125˚C Remote Diode Junction Package Dissipation at TA = 25˚C (Note 4) + Positive Supply Voltage (V ) 900mW Maximum V O_CRIT, V and V O_SP1 Soldering Information MSOP Package (Note 6) : Vapor Phase (60 seconds) +2.8V to +3.8V O_SP0 +5.
PAGE 4
LM88 LM88 Electrical Characteristics (Continued) Note 2: When the input voltage (VI) at any pin exceeds the power supply (VI < GND or VI > V+), the current at that pin should be limited to 5mA. The 20mA maximum package input current rating limits the number of pins that can safely exceed the power supplies with an input current of 5mA to four. Note 3: Parasitics or ESD protection circuitry are shown in the diagram found below. The ESD Clamp circtuitry is triggered on when there is an ESD event.
PAGE 5
LM88 1.0 Functional Description 10132611 a) When programmed for a greater than comparison 10132612 b) When programmed for a less than comparison FIGURE 2. Comparator output temperature response diagrams dition, to T_CRIT ± 1˚C is false. The CRIT comparator can be factory programmed to make a greater than or less than comparison. (See Section 1.3 LM88 OPTIONS) 1.1 PIN DESCRIPTIONS V+ This is the positive supply voltage pin, which has a range of 2.8 to 3.8 volts. This pin should be bypassed with a 0.
PAGE 6
LM88 1.0 Functional Description (Continued) 1.2 TYPICAL PIN CONNECTION Pin Label Pin Number Typical Connection D0+ 1 3904-type transistor shorted-collector base or Pentium thermal diode anode; 2.2nF capacitor connected to D- D− 2 3904-type transistor emitter or Pentium thermal diode cathode (individual traces are required to each diode; do not daisy chain); two 2.2nF capacitors connected to D0+ and D1+ D1+ 3 3904-type transistor shorted collector-base or Pentium thermal diode anode; 2.
PAGE 7
temperature sensor. The only other parameter is η, which depends on the diode that is used for measurement. Since ∆VBE is proportional to both η and T, the variations in η cannot be distinguished from variations in temperature. Since the non-ideality factor is not controlled by the temperature sensor, it will directly add to the inaccuracy of the sensor. For the Pentium II, Intel specifies a ± 1% variation in η from part to part.
PAGE 8
LM88 2.0 Application Hints as much as 1˚C of error in the diode temperature reading. Keeping the printed circuit board as clean as possible will minimize leakage current. (Continued) 8. The ideal place to connect the LM88’s GND pin is as close as possible to the processor GND associated with the sense diode. 9. Leakage current between D+ and GND should be kept to a minimum. One nano-ampere of leakage can cause 10132633 FIGURE 4. Ideal Diode Trace Layout 3.
PAGE 9
LM88 Factory Programmable Dual Remote-Diode Thermostat Physical Dimensions inches (millimeters) unless otherwise noted 8-Lead Molded Mini Small Outline Package (MSOP) (JEDEC REGISTRATION NUMBER M0-187) Order Number LM88CIMM, or LM88CIMMX NS Package Number MUA08A LIFE SUPPORT POLICY NATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT AND GENERAL COUNSEL OF NATIONAL SEMICONDUCTOR CORPORATION.