Rainbow Electronics LM77 User Manual

LM77
9-Bit + Sign Digital Temperature Sensor and Thermal
Window Comparator with Two-Wire Interface

July 2001

LM77 9-Bit + Sign Digital Temperature Sensor and Thermal Window Comparator with Two-Wire

Interface

General Description

The LM77 is a digital temperature sensor and thermal win­dow comparator with an I
window-comparator architecture of the LM77 eases the de­sign of temperature control systems conforming to the ACPI
(Advanced Configuration and Power Interface) specification
for personal computers. The open-drain Interrupt (INT) out­put becomes active whenever temperature goes outside a
programmable window, while a separate Critical Tempera­ture Alarm (T_CRIT_A) output becomes active when the
temperature exceeds a programmable critical limit. The INT
output can operate in either a comparator or event mode,
while the T_CRIT_A output operates in comparator mode
only.

The host can program both the upper and lower limits of the
window as well as the critical temperature limit. Program­mable hysterisis as well as a fault queue are available to
minimize false tripping. Two pins (A0, A1) are available for
address selection.The sensor powers upwith default thresh­olds of 2˚C T
T_CRIT.

The LM77’s 3.0V to 5.5V supply voltage range, Serial Bus
interface, 9-bit + sign output, and full-scale range of over
128˚C make it ideal for a wide range of applications. These
include thermal management and protection applications in
personal computers, electronic test equipment, office elec­tronics, automotive, and HVAC applications.

HYST

, 10˚C T

2

C™Serial Bus interface. The

LOW

, 64˚C T

, and 80˚C

HIGH

Features

n Window comparison simplifies design of ACPI

compatible temperature monitoring and control.

n Serial Bus interface
n Separate open-drain outputs for Interrupt and Critical

Temperature shutdown

n Shutdown mode to minimize power consumption
n Up to 4 LM77s can be connected to a single bus
n 9-bit + sign output; full-scale reading of over 128˚C
n SOP and MSOP 8-lead packages

Key Specifications

j

Supply Voltage 3.0V to 5.5V

j

Supply Current operating 250 µA (typ)

500 µA (max)

shutdown 5 µA (typ)

j

Temperature

Accuracy

−10˚C to 65˚C

−25˚C to 100˚C

−55˚C to 125˚C

±

1.5˚C(max)

±

2˚C(max)

±

3˚C(max)

Applications

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

I2C®is a registered trademark of Philips Corporation.

© 2001 National Semiconductor Corporation DS100136 www.national.com

Simplified Block Diagram

LM77

Connection Diagram

DS100136-1

SOP8 or MSOP

DS100136-2

LM77 See NS Package Number M08A or MM08A

Ordering Information

Order Number Supply Voltage Package Supplied In

LM77CIM-3 3.3V SOP8, M08A Rail
LM77CIMX-3 3.3V SOP8, M08A 2500 Units on Tape and Reel
LM77CIM-5 5V SOP8, M08A Rail
LM77CIMX-5 5V SOP8, M08A 2500 Units on Tape and Reel
LM77CIMM-3 3.3V MSOP8,

MUA08A

LM77CIMMX-3 3.3V MSOP8,

MUA08A

LM77CIMM-5 5V MSOP8,

MUA08A

LM77CIMMX-5 5V MSOP8,

MUA08A

Rail

3500 Units on Tape and Reel

Rail

3500 Units on Tape and Reel

Pin Description

Label Pin

SDA 1 Serial Bi-Directional Data Line. Open Drain Output From Controller
SCL 2 Serial Bus Clock Input From Controller
T_CRIT_A 3 Critical Temperature Alarm Open Drain Output Pull Up Resistor, Controller Interrupt Line

GND 4 Power Supply Ground Ground
INT 5 Interrupt Open Drain Output Pull Up Resistor, Controller Interrupt Line
+V

S

A0–A1 7,6 User-Set Address Inputs Ground (Low, “0”) or +V

#

8 Positive Supply Voltage Input DC Voltage from 3V to 5.5V

Function Typical Connection

or System Hardware Shutdown

S

(High, “1”)

www.national.com 2

Pin Description (Continued)

LM77

DS100136-3

FIGURE 1. Typical Application

www.national.com3

Absolute Maximum Ratings (Note 1)

LM77

Supply Voltage −0.3V to 6.5V
Voltage at any Pin −0.3V to (+V
Input Current at any Pin 5 mA
Package Input Current (Note 2) 20 mA
T_CRIT_A and INT Output Sink

Current 10 mA
T_CRIT_A and INT Output

+ 0.3V )

S

Soldering Information, Lead
Temperature

SOP and MSOP 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

Voltage 6.5V
Storage Temperature −65˚C to +125˚C

Operating Ratings (Notes 1, 5)

Specified Temperature Range T
(Note 6) −55˚C to +125˚C
Supply Voltage Range (+V

)(Note 7) +3.0V to +5.5V

S

Temperature-to-Digital Converter Characteristics

Unless otherwise noted, these specifications apply for +VS=+5 Vdc±10% for LM77CIM-5, LM77CIMM-5 and +VS=+3.3 Vdc

±

10% for LM77CIM-3, LM77CIMM-3 (Note 7). Boldface limits apply for TA=TJ=T

T

=+25˚C, unless otherwise noted.

J

Parameter Conditions

Accuracy T

= −10˚C to +65˚C

A

= −25˚C to +100˚C

A

T

= −55˚C to +125˚C

A

Typical

(Note 8)

Resolution (Note 10) 10

0.5
Temperature Conversion Time (Note 11) 70 125 ms
Quiescent Current I

2

C Inactive 0.25 mA

2

I

C Active 0.25 0.5 mA (max)

Shutdown Mode 5 10 µA

T

Default Temperature (Notes 13, 14) 2 ˚C

HYST

T

Default Temperature (Note 14) 10 ˚C

LOW

T

Default Temperature (Note 14) 64 ˚C

HIGH

T

Default Temperature (Note 14) 80 ˚C

C

MIN

to T

MAX

Limits

(Note 9)

±

1.5

±

2.0

±

3.0

; all other limits TA=

MIN

Units

(Limit)

˚C (max)T

Bits

˚C

to T

MAX

Logic Electrical Characteristics

DIGITAL DC CHARACTERISTICS Unless otherwise noted, these specifications apply for +VS=+5 Vdc±10% for LM77CIM-5,

LM77CIMM-5 and +V
other limits T

A=TJ

Symbol Parameter Conditions

V

IN(1)

V

IN(0)

V

IN(1)

V

IN(0)

I

IN(1)

I

IN(0)

C

IN

www.national.com 4

=+3.3 Vdc±10% for LM77CIM-3, LM77CIMM-3. Boldface limits apply for TA=TJ=T

S

MIN

to T

=+25˚C, unless otherwise noted.

Typical

(Note 8)

SDA and SCL Logical “1” Input

Limits

(Note 9)

+VSx 0.7 V (min)

Voltage

+V

+0.3 V (max)

S

SDA and SCL Logical “0” Input

−0.3 V (min)

Voltage

+V

x 0.3 V (max)

S

A0 and A1 Logical “1” Input

2.0 V (min)

Voltage

+V

+0.3 V (max)

S

A0 and A1 Logical “0” Input

−0.3 V (min)

Voltage

0.8 V (max)

Logical “1” Input Current VIN=+V

S

0.005 1.0 µA (max)
Logical “0” Input Current VIN= 0V −0.005 −1.0 µA (max)
Capacitance of All Digital Inputs 20 pF

MAX

Units

(Limit)

; all

Logic Electrical Characteristics (Continued)

DIGITAL DC CHARACTERISTICS Unless otherwise noted, these specifications apply for +VS=+5 Vdc±10% for LM77CIM-5,

LM77CIMM-5 and +V
other limits T

A=TJ

Symbol Parameter Conditions

I

OH

V

OL

t

OF

=+3.3 Vdc±10% for LM77CIM-3, LM77CIMM-3. Boldface limits apply for TA=TJ=T

S

MIN

to T

MAX

=+25˚C, unless otherwise noted.

High Level Output Current VOH=+V

Typical

(Note 8)

S

Limits

(Note 9)

(Limit)

10 µA (max)

Units

Low Level Output Voltage IOL=3mA 0.4 V (max)
T_CRIT_A Output Saturation

Voltage

I

= 4.0 mA

OUT

(Note 12)

0.8 V (max)

T_CRIT_A Delay 1 Conversions

(max)

Output Fall Time CL= 400 pF 250 ns (max)

I

=3mA

O

LM77

; all

www.national.com5

Logic Electrical Characteristics (Continued)

LM77

SERIAL BUS DIGITAL SWITCHING CHARACTERISTICS Unless otherwise noted, these specifications apply for +VS=+5 Vdc

±

10% for LM77CIM-5 and LM77CIMM-5, +VS=+3.3 Vdc±10% for LM77CIM-3 and LM77CIMM-3, CL (load capacitance) on

output lines = 80 pF unless otherwise specified. Boldface limits apply for T

A=TJ=TMIN

+25˚C, unless otherwise noted.
The switching characteristics of the LM77 fully meet or exceed the published specifications of the I
rameters are the timing relationship between SCL and SDA signal related to the LM77. They are not the I

Symbol Parameter Conditions

t

1

t

2

t

3

t

4

t

5

SCL (Clock) Period 2.5 µs(min)
Data in Set-Up Time to SCL High 100 ns(min)
Data Out Stable after SCL Low 0 ns(min)
SDA Low Set-Up Time to SCL Low (Start Condition) 100 ns(min)
SDA High Hold Time after SCL High (Stop Condition) 100 ns(min)

to T

; all other limits TA=TJ=

MAX

2

C bus. The following pa-

2

Typical

(Note 8)

(Note 9)

C bus specifications.

Limits

Units

(Limit)

DS100136-4

Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. DC and AC electrical specifications do not apply when operating
the device beyond its rated operating conditions.

Note 2: When the input voltage (V
maximum package input current rating limits the number of pins that can safely exceed the power supplies with an input current of 5 mA to four.

Note 3: See AN-450 “Surface Mounting Methods and Their Effect on Product Reliability” or the section titled “Surface Mount” found in a current National
Semiconductor Linear Data Book for other methods of soldering surface mount devices.

Note 4: Human body model, 100 pF discharged through a 1.5 kΩ resistor. Machine model, 200 pF discharged directly into each pin.
Note 5: LM77 θ

250˚C/W for the MSOP-8 (MUA08A) package.

Note 6: While the LM77 has a full-scale-range in excess of 128˚C, prolonged operation at temperatures above 125˚C is not recommended.
Note 7: Both part numbers of the LM77 will operate properly over the +V

accuracy at their nominal supply voltage. Accuracy will typically degrade 1˚C/V of variation in +V

Note 8: Typicals are at T
Note 9: Limits are guaranteed to National’s AOQL (Average Outgoing Quality Level).
Note 10: 9 bits + sign, two’s complement
Note 11: This specification is provided only to indicate how often temperature data is updated. The LM77 can be read at any time without regard to conversion state

(and will yield last conversion result). If a conversion is in process it will be interrupted and restarted after the end of the read.
Note 12: For best accuracy,minimize output loading. Higher sink currents can affect sensor accuracy with internal heating. This can cause an error of 0.64˚C at full

rated sink current and saturation voltage based on junction-to-ambient thermal resistance.
Note 13: Hysteresis value adds to the T

subtracts from the T
discussion of the function of hysteresis refer to

Note 14: Default values set at power up.

(thermal resistance, junction-to-ambient) when attached to a printed circuit board with 2 oz. foil is: 200˚C/W for the SOP-8 (M08A) package,

JA

HIGH

) at any pin exceeds the power supplies (V

I

= 25˚C and represent most likely parametric norm.

A

setpoint value (e.g.: if T

and T_CRIT setpoints (e.g.: if T

LOW

Section 1.1

HIGH

LOW

setpoint = 64˚C, and hysteresis = 2˚C, then actual hysteresis point is 64−2 = 62˚C). For a detailed

, TEMPERATURE COMPARISON, and

<

GND or V

I

supply voltage range of 3V to 5.5V . The devices are tested and specified for rated

S

setpoint = 10˚C, and hysteresis = 2˚C, then actual hysteresis point is 10+2 = 12˚C); and

>

+VS) the current at that pin should be limited to 5 mA. The 20 mA

I

as it varies from the nominal value.

S

Figure 3

.

www.national.com 6