Rainbow Electronics LM84 User Manual

July 2000

LM84
Diode Input Digital Temperature Sensor with Two-Wire
Interface

General Description

The LM84 is a remote diode temperature sensor,
Delta-Sigma analog-to-digital converter, and digital
over-temperature detector with an SMBus
LM84 senses its own temperature as well as the tempera­ture of a target IC with a diode junction, such as a Pentium
II processor or a diode connected 2N3904. A diode junction
(semiconductor junction) is required on the target IC’s die. A
host can query the LM84 at any time to read the temperature
of this diode as well as the temperature state of the LM84
itself.AT_CRIT_A interrupt output becomes active when the
temperature is greater than a programmable comparator
limit, T_CRIT.

The host can program as well as read back the state of the
T_CRIT register. Three state logic inputs allow two pins
(ADD0,ADD1) to select up to 9 SMBus address locations for
the LM84. The sensor powers up with default thresholds of
127˚C for T_CRIT.

™

interface. The

Features

n Directly senses die temperature of remote ICs
n Senses temperature of remote diodes
n SMBus compatible interface, supports SMBus Timeout

n Register readback capability
n 7 bit plus sign temperature data format
n 2 address select lines enable 9 LM84s to be connected

to a single bus

®

Key Specifications

j

Supply Voltage 3.0V - 3.6V

j

Supply Current 1 mA (max)

j

Local Temperature Accuracy

j

Remote Diode Temperature Accuracy

+60˚C to +100˚C

0˚C to +125˚C

Applications

n System Thermal Management
n Personal Computers
n Electronic Test Equipment
n Office Electronics
n HVAC

±

1.0˚C (typ)

±

3˚C (max)

±

5˚C (max)

LM84 Diode Input Digital Temperature Sensor with Two-Wire Interface

Simplified Block Diagram

#

Indicates Active Low (”NOT“)

SMBus™is a trademark of the Intel Corporation.

®

Pentium

II processor is a registered trademark of the Intel Corporation.

®

I2C

is a registered trademark of the Philips Corporation.

DS100961-1

© 2001 National Semiconductor Corporation DS100961 www.national.com

Connection Diagram

LM84

Ordering Information

QSOP-16

DS100961-2

TOP VIEW

Order

Number

LM84BIMQA

LM84BIMQAX

LM84CIMQA

LM84CIMQAX

Typical Application

NS

Package

Number

MQA16A

(QSOP-16)

MQA16A

(QSOP-16)

MQA16A

(QSOP-16)

MQA16A

(QSOP-16)

Transport

Media

95 Units in

Rail

2500 Units on

Tape and

Reel

95 Units in

Rail

2500 Units on

Tape and

Reel

SMBus

Revision

Level

1.1 20MHz

1.1 20MHz

1.0 Not Available

1.0 Not Available

Noise Filter

on SMBCLK

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DS100961-3

Pin Descriptions

LM84

Label Pin

#

Function Typical Connection

Manufacturing test pins. Left floating. PC board traces may be routed

NC

V

CC

1, 5, 9,

13, 16

2

Positive Supply Voltage
Input

Diode Current Source To Diode Anode. Connected to remote discrete

D+ 3

D− 4

ADD0–ADD1 10, 6

Diode Return Current
Sink

User-Set SMBus (I

2

Address Inputs

C)

GND 7, 8 Power Supply Ground Ground

T_CRIT_A

SMBData 12

11

Critical Temperature
Alarm, open-drain output

SMBus (I

2

C) Serial
Bi-Directional Data Line,
open-drain output

2

SMBCLK 14 SMBus (I

NC 15

No Connection Left floating. PC board traces may be routed

C) Clock Input From Controller

through the pads for these pins. Although, the
components that drive these traces should share
the same supply as the LM84 so that the Absolute
Maximum Voltage at any Pin rating is not violated.

DC Voltage from 3.0V to 3.6V

diode or to the diode on the external IC whose die
temperature is being sensed.

To Diode Cathode. Must be grounded when not
used.

Ground (Low, “0”), VCC(High, “1”) or open
(“TRI-LEVEL”)

Pull Up Resistor, Controller Interrupt Line or
System Shutdown

From and to Controller, Pull Up Resistor

through the pads for this pin.

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Absolute Maximum Ratings (Note 1)

LM84

Supply Voltage −0.3V to 6.0V
Voltage at Any Pin:

NC (Pins 1,5,9), ADD0, ADD1, D

+

All other pins (except D−) −0.3V to 6.0V

D− Input Current

(V

−0.3V to
+ 0.3V)

CC

±

1mA

Soldering Information, Lead Temperature
QSOP Package (Note 3)

Vapor Phase (60 seconds) 215˚C
Infrared (15 seconds) 220˚C

ESD Susceptibility (Note 4)

Human Body Model 2500V
Machine Model 250V

Input Current at All Other Pins (Note

2) 5 mA
Package Input Current (Note 2) 20 mA
SMBData, T_CRIT_A Output Sink

Current 10 mA
Output Voltage 6.0V
Storage Temperature −65˚C to +150˚C

Operating Ratings

(Note 1) and (Note 5)
Specified Temperature Range T

LM84 0˚C to +125˚C
Supply Voltage Range (V

) +3.0V to +3.6V

CC

Temperature-to-Digital Converter Characteristics

Unless otherwise noted, these specifications apply for VCC=+3.0 Vdc to +3.6 Vdc. Boldface limits apply for TA=TJ=T
to T

Local Temperature Error (Note 8)
Remote Temperature Error using

Pentium Diode (Note 8) and (Note

9)

Remote Temperature Error using
Diode Connected 2N3904 (Note 8)
and (Note 9)

Resolution 8 Bits

Temperature Conversion Time (Note 11) 120 145 ms
Quiescent Current (Note 10) SMBus (I
D− Source Voltage 0.7 V
Diode Source Current (D+ − D−)=+ 0.65V; high

T_CRIT_A Output Saturation
Voltage

Power-On Reset Threshold On V

Local and Remote T_CRIT Default
Temperature

; all other limits TA=TJ=+25˚C, unless otherwise noted.

MAX

Parameter Conditions Typical Limits Units

(Note 6) (Note 7) (Limit)

±

1˚C

+60˚C ≤T

= 3.3 Vdc

V

CC

0˚C ≤ T

= 3.3 Vdc

V

CC

+60˚C ≤T

= 3.3 Vdc

V

CC

0˚C ≤ T

= 3.3 Vdc

V

CC

≤ +100˚C,

A

≤ +125˚C,

A

≤ +100˚C,

A

≤ +125˚C,

A

±

3

±

5 ˚C (max)

+1, −5 ˚C (max)

+3, −7 ˚C (max)

1˚C

2

C Inactive) 0.500 1 mA (max)

160 µA (max)

level

50 µA (min)

Low level 16 µA (max)

5 µA (min)

I

= 3.0 mA 0.4

OUT

edge

input, falling

CC

2.2

1.2

(Note 12) +127 ˚C

to T

MIN

˚C (max)

V (max)
V (max)

V (min)

MAX

MIN

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Logic Electrical Characteristics

DIGITAL DC CHARACTERISTICS

Unless otherwise noted, these specifications apply for V

T

; all other limits TA=TJ=+25˚C, unless otherwise noted.

MAX

Symbol Parameter Conditions Typical LM84B LM84C Units

SMBData, SMBCLK

V
V
I
I

IN(1)

IN(0)
IN(1)
IN(0)

Logical “1” Input Voltage 2.1 1.4 V (min)
Logical “0”Input Voltage 0.8 0.6 V (max)
Logical “1” Input Current VIN=V
Logical “0” Input Current VIN= 0V −0.005 −1.0 −1.0 µA (max)

ADD0, ADD1

V
V
I
I

IN(1)

IN(0)
IN(1)
IN(0)

Logical “1” Input Voltage V
Logical “0”Input Voltage GND 0.5 0.5 V (max)
Logical “1” Input Current VIN=V
Logical “0” Input Current VIN=0V 50 600 600 µA (max)

ALL DIGITAL INPUTS

C

IN

Input Capacitance 20 pF

ALL DIGITAL OUTPUTS

I

OH

V

OL

High Level Output Current VOH=V
SMBus Low Level Output

Voltage

=+3.0 to 3.6 Vdc. Boldface limits apply for TA=TJ=T

CC

(Note 6) Limits

(Note 7)

CC

CC

CC

IOL=3mA

=6mA

I

OL

0.005 1.0 1.0 µA (max)

CC

1.6 1.6 V (min)

50 600 600 µA (max)

100 100 µA (max)

0.4

0.6

Limits

(Note 7)

0.4

0.6

MIN

V (max)

LM84

to

(Limit)

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