Rainbow Electronics LM70 User Manual

February 2005

LM70
SPI/MICROWIRE 10-Bit plus Sign Digital Temperature
Sensor

LM70 SPI/MICROWIRE

General Description

The LM70 is a temperature sensor, Delta-Sigma analog-to­digital converter with an SPI and MICROWIRE compatible
interface available in LLP and MSOP 8-pin packages. The
host can query the LM70 at any time to read temperature. A
shutdown mode decreases power consumption to less than
10 µA. This mode is useful in systems where low average
power consumption is critical.

The LM70 has 10-bit plus sign temperature resolution
(0.25˚C per LSB) while operating over a temperature range
of −55˚C to +150˚C.

The LM70’s 2.65V to 5.5V supply voltage range, low supply
current and simple SPI interface make it ideal for a wide
range of applications. These include thermal management
and protection applications in hard disk drives, printers, elec­tronic test equipment, and office electronics.

Applications

n System Thermal Management
n Personal Computers
n Disk Drives
n Office Electronics
n Electronic Test Equipment

Features

n 0.25˚C temperature resolution.
n Shutdown mode conserves power between temperature

reading

n SPI and MICROWIRE Bus interface
n MSOP-8 and LLP-8 packages save space

Key Specifications

j

Supply Voltage 2.65V to 5.5V

j

Supply Current operating 260 µA (typ)

490 µA (max)

shutdown 12 µA (typ)

j

Temperature

Accuracy

−40˚C to 85˚C

−10˚C to 65˚C +1.5/−2˚C(max)

−55˚C to 125˚C +3/−2˚C(max)

−55˚C to 150˚C +3.5/−2˚C(max)

±

2˚C(max)

™

10-Bit plus Sign Digital Temperature Sensor

Simplified Block Diagram

10122301

© 2005 National Semiconductor Corporation DS101223 www.national.com

Connection Diagrams

LM70

MSOP-8 LLP-8

TOP VIEW

NS Package Number MUA08A

10122302

10122325

TOP VIEW

NS Package Number LDA08A

Ordering Information

Order Number

LM70CILD-3 T33 LLP-8, LDA08A 2.65V to 3.6V 1000 Units in Tape and Reel

LM70CILDX-3 T33 LLP-8, LDA08A 2.65V to 3.6V 4500 Units in Tape and Reel

LM70CILD-5 T35 LLP-8, LDA08A 4.5V to 5.5V 1000 Units in Tape and Reel

LM70CILDX-5 T35 LLP-8, LDA08A 4.5V to 5.5V 4500 Units in Tape and Reel

LM70CIMM-3 T04C MSOP-8, MUA08A 2.65V to 3.6V 1000 Units in Tape and Reel

LM70CIMMX-3 T04C MSOP-8, MUA08A 2.65V to 3.6V 3500 Units in Tape and Reel

LM70CIMM-5 T03C MSOP-8, MUA08A 4.5V to 5.5V 1000 Units in Tape and Reel

LM70CIMMX-5 T03C MSOP-8, MUA08A 4.5V to 5.5V 3500 Units in Tape and Reel

Package

Marking

NS Package

Number

Supply Voltage Transport Media

Pin Descriptions

Label SOP-8

Pin #

SI/O 1 1 Input/Output - Serial bus bi-directional data line.

SC 2 3 Clock - Serial bus clock Schmitt trigger input

GND 4 7 Power Supply Ground Ground

+

V

CS 7 8 Chip Select input. From Controller

NC 3, 6, 8 2, 4, 6 No Connect These pins are not connected to the

5 5 Positive Supply Voltage Input DC Voltage from 2.65V to 5.5V. Bypass

LLP-8

Pin #

Function Typical Connection

From and to Controller

Schmitt trigger input.

From Controller

line.

with a 0.1 µF ceramic capacitor.

LM70 die in any way.

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Typical Application

LM70

10122303

FIGURE 1. COP Microcontroller Interface

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Absolute Maximum Ratings (Note 1)

LM70

Supply Voltage −0.3V to 6.0V

Voltage at any Pin −0.3V to V

+

+ 0.3V

ESD Susceptibility (Note 4)

Human Body Model 3000V

Machine Model 300V

Input Current at any Pin (Note 2) 5 mA

Package Input Current (Note 2) 20 mA

Storage Temperature −65˚C to +150˚C

Soldering Information, Lead Temperature

MSOP-8 and LLP-8 Packages

(Note 3)

Vapor Phase (60 seconds)
Infrared (15 seconds)

215˚C
220˚C

Operating Ratings

Specified Temperature Range T

(Note 5) −55˚C to +150˚C

Supply Voltage Range (+V

) +2.65V to +5.5V

S

Temperature-to-Digital Converter Characteristics

Unless otherwise noted, these specifications apply for V+= 2.65V to 3.6V for the LM70-3 and V+= 4.5V to 5.5V for the LM70-5
(Note 6). Boldface limits apply for T

A=TJ=TMIN

to T

Parameter Conditions

Temperature Error (Note 6) T

= −10˚C to +65˚C +1.5/−2.0 +1.5/−2.0 ˚C (max)

A

T

= −40˚C to +85˚C

A

T

= −55˚C to +125˚C +3.0/−2.0 +3.0/−2.0 ˚C (max)

A

T

= −55˚C to +150˚C +3.5/−2.0 +3.5/−2.0 ˚C (max)

A

Resolution 11

Temperature Conversion

(Note 9) 140 210 210 ms (max)

Time

Quiescent Current Serial Bus Inactive 260 490 490 µA (max)

Serial Bus Active 260 µA

Shutdown Mode 12 µA

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

MAX

Typical

(Note 7)

LM70-5

Limits

(Note 8)

±

2.0

LM70-3

Limits

(Note 8)

±

2.0 ˚C (max)

0.25

(Limit)

MIN

Units

Bits

˚C

to T

MAX

Logic Electrical Characteristics
Digital DC Characteristics

Unless otherwise noted, these specifications apply for V+= 2.65V to 3.6V for the LM70-3 and V+= 4.5V to 5.5V for the
LM70-5. Boldface limits apply for T

A=TJ=TMIN

to T

Symbol Parameter Conditions

V

IN(1)

V

IN(0)

Logical “1” Input Voltage V+x 0.7 V (min)

Logical “0” Input Voltage −0.3 V (min)

Input Hysteresis Voltage V

V

I

IN(1)

I

IN(0)

C

IN

V

OH

V

OL

I

O_TRI-STATE

Logical “1” Input Current VIN=V

Logical “0” Input Current VIN= 0V −0.005 −3.0 µA (min)

All Digital Inputs 20 pF

High Level Output Voltage IOH= −400 µA 2.4 V (min)

Low Level Output Voltage IOL=+2mA 0.4 V (max)

TRI-STATE Output Leakage
Current

VO= GND
V

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

MAX

Typical

(Note 7)

+

= 2.65V to 3.6V 0.8 0.27 V (min)

+

= 4.5V to 5.5V 0.8 0.35 V (min)

+

0.005 3.0 µA (max)

Limits

(Note 8)

+

V

+ 0.3 V (max)

+

V

x 0.3 V (max)

−1

+

=V

O

+1

Units

(Limit)

µA (min)

µA (max)

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Logic Electrical Characteristics (Continued)

Serial Bus Digital Switching Characteristics

Unless otherwise noted, these specifications apply for V+= 2.65V to 3.6V for the LM70-3 and V+= 4.5V to 5.5V for the
LM70-5, C

to T

MAX

Symbol Parameter Conditions

t

1

(load capacitance) on output lines = 100 pF unless otherwise specified. Boldface limits apply for TA=TJ=T

L

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

Typical

(Note 7)

Limits

(Note 8)

SC (Clock) Period 0.16

DC

t

2

t

3

t

4

t

5

t

6

t

7

CS Low to SC (Clock) High Set-Up Time 100 ns (min)

CS Low to Data Out (SO) Delay 70 ns (max)

SC (Clock) Low to Data Out (SO) Delay 70 ns (max)

CS High to Data Out (SO) TRI-STATE 200 ns (min)

SC (Clock) High to Data In (SI) Hold Time 60 ns (min)

Data In (SI) Set-Up Time to SC (Clock) High 30 ns (min)

Timing Diagrams

LM70

MIN

Units

(Limit)

µs (min)

(max)

FIGURE 2. Data Output Timing Diagram

FIGURE 3. TRI-STATE Data Output Timing Diagram

10122304

10122305

FIGURE 4. Data Input Timing Diagram

10122306

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Electrical Characteristics

LM70

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 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: The life expectancy of the LM70 will be reduced when operating at elevated temperatures. LM70 θ

attached to a printed circuit board with 2 oz. foil is summarized in the table below:

) at any pin exceeds the power supplies (V

I

Device Number

<

GND or V

I

NS Package

Number

>

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

I

(thermal resistance, junction-to-ambient) when

JA

Thermal

Resistance (θ

)

JA

LM70CILD LDA08A 51.3˚C/W

LM70CIMM MUA08A 200˚C/W

Note 6: Both part numbers of the LM70 will operate properly over the V+supply voltage range of 2.65V to 5.5V. The temperature error for temperature ranges of

−10˚C to +65˚C, −40˚C to +85˚C, −55˚C to +125˚C and −55˚C to +150˚C include error induced by power supply variation of
Temperature error will increase by

Note 7: Typicals are at T

Note 8: Limits are guaranteed to National’s AOQL (Average Outgoing Quality Level).

Note 9: This specification is provided only to indicate how often temperature data is updated. The LM70 can be read at any time without regard to conversion state

(and will yield last conversion result). A conversion in progress will not be interrupted. The output shift register will be updated at the completion of the read and a
new conversion restarted.

Note 10: 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.

±

0.3˚C for a power supply voltage (V+) variation of±10% from the nominal value.

= 25˚C and represent most likely parametric norm.

A

±

5% from the nominal value.

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Electrical Characteristics (Continued)

FIGURE 5. Temperature-to-Digital Transfer Function (Non-linear scale for clarity)

LM70

10122308

TRI-STATE Test Circuit

10122307

FIGURE 6.

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Typical Performance Characteristics

LM70

Average Power-On Reset Voltage vs Temperature Static Supply Current vs Temperature

Temperature Error

10122323 10122321

10122322

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1.0 Functional Description

The LM70 temperature sensor incorporates a band-gap type
temperature sensor and 10-bit plus sign ∆Σ ADC (Delta­Sigma Analog-to-Digital Converter). Compatibility of the
LM70’s three wire serial interface with SPI and MICROWIRE
allows simple communications with common microcontrol­lers and processors. Shutdown mode can be used to opti­mize current drain for different applications. A manufacture’s
ID register identifies the LM70 as National Semiconductor
product.

1.1 POWER UP AND POWER DOWN

The LM70 always powers up in a known state. The power up
default condition is continuous conversion mode. Immediatly
after power up the LM70 will output an erroneous code until
the first temperature conversion has completed.

When the supply voltage is less than about 1.6V (typical),
the LM70 is considered powered down. As the supply volt­age rises above the nominal 1.6V power up threshold, the
internal registers are reset to the power up default state
described above.

7F hex(normal operation)

•

FF hex (Shutdown, transmit manufacturer’s ID)

•

.
any others may place the part into a Test Mode. Test Modes

are used by National Semiconductor to thoroughly test the
function of the LM70 during production testing. Only eight
bits have been defined above since only the last eight trans­mitted, before CS is taken HIGH, are detected by the LM70

The following communication can be used to determine the
Manufacturer’s/Device ID and then immediately place the
part into continuous conversion mode. With CS continuously
low:

Read 16 bits of temperature data

•

Write 16 bits of data commanding shutdown

•

Read 16 bits of Manufacture’s/Device ID data

•

Write 8 to 16 bits of data commanding Conversion Mode

•

Take CS HIGH.

•

Note that 250 ms will have to pass for a conversion to
complete before the LM70 actually transmits temperature
data.

LM70

1.2 SERIAL BUS INTERFACE

The LM70 operates as a slave and is compatible with SPI or
MICROWIRE bus specifications. Data is clocked out on the
falling edge of the serial clock (SC), while data is clocked in
on the rising edge of SC. A complete transmit/receive com­munication will consist of 32 serial clocks. The first 16 clocks
comprise the transmit phase of communication, while the
second 16 clocks are the receive phase.

®

When CS is high SI/O will be in TRISTATE
should be initiated by taking chip select (CS) low. This
should not be done when SC is changing from a low to high
state. Once CS is low the serial I/O pin (SI/O) will transmit
the first bit of data. The master can then read this bit with the
rising edge of SC. The remainder of the data will be clocked
out by the falling edge of SC. Once the 14 bits of data (one
sign bit, ten temperature bits and 3 high bits) are transmitted
the SI/O line will go into TRI-STATE. CS can be taken high at
any time during the transmit phase. If CS is brought low in
the middle of a conversion the LM70 will complete the con­version and the output shift register will be updated after CS
is brought back high.

The receive phase of a communication starts after 16 SC
periods. CS can remain low for 32 SC cycles. The LM70 will
read the data available on the SI/O line on the rising edge of
the serial clock. Input data is to an 8-bit shift register. The
part will detect the last eight bits shifted into the register. The
receive phase can last up to 16 SC periods. All ones must be
shifted in order to place the part into shutdown. A zero in any
location will take the LM70 out of shutdown. The following
codes only should be transmitted to the LM70:

00 hex (normal operation)

•

01 hex (normal operation)

•

03 hex (normal operation)

•

07 hex (normal operation)

•

0F hex (normal operation)

•

1F hex (normal operation)

•

3F hex(normal operation)

•

. Communication

1.3 TEMPERATURE DATA FORMAT

Temperature data is represented by a 11-bit, two’s comple­ment word with an LSB (Least Significant Bit) equal to

0.25˚C:

Temperature Digital Output

Binary Hex

+150˚C 0100 1011 0001 1111 4B 1F h

+125˚C 0011 1110 1001 1111 3E 9Fh

+25˚C 0000 1100 1001 1111 0B 9Fh

+0.25˚C 0000 0000 0011 1111 0 0 3 Fh

0˚C 0000 0000 0001 1111 00 1Fh

−0.25˚C 1111 1111 1111 1111 F F F Fh

−25˚C 1111 0011 1001 1111 F3 9Fh

−55˚C 1110 0100 1001 1111 E4 9Fh

Note: The last two bits are TRI-STATE and depicted as one
in the table.

The first data byte is the most significant byte with most
significant bit first, permitting only as much data as neces­sary to be read to determine temperature condition. For
instance, if the first four bits of the temperature data indicate
an overtemperature condition, the host processor could im­mediately take action to remedy the excessive tempera­tures.

1.4 SHUTDOWN MODE/MANUFACTURER’S ID

Shutdown mode is enabled by writing XX FF to the LM70 as
shown in Figure 7c and discussed in Section 1.2. The serial
bus is still active when the LM70 is in shutdown. Current
draw drops to less than 10 µA between serial communica­tions. When in shutdown mode the LM70 always will output
1000 0001 0000 00XX. This is the manufacturer’s ID/Device
ID information. The first 5-bits of the field (1000 0XXX) are
reserved for manufacturer’s ID.

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1.0 Functional Description (Continued)

LM70

1.5 INTERNAL REGISTER STRUCTURE

The LM70 has three registers, the temperature register, the
configuration register and the manufacturer’s/device identifi­cation register. The temperature and manufacturer’s/device
identification registers are read only. The configuration reg­ister is write only.

1.5.1 CONFIGURATION REGISTER

(Selects shutdown or continuous conversion modes):

(Write Only):

D15 D14 D13 D12 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0

XXXXXXXX Shutdown

D0-D15 set to XX FF hex enables shutdown mode.
D0-D15 set to XX 00 hex enables continuous conversion

mode.
Note: setting D0-D15 to any other values may place the

LM70 into a manufacturer’s test mode, upon which the LM70

1.5.2 TEMPERATURE REGISTER

(Read Only):

D15 D14 D13 D12 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0

MSB Bit 9 Bit 8 Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 LSB 1 1 1 X X

D0–D1: Undefined. TRI-STATE will be output on SI/0.
D2–D4: Always set high.

1.5.3 MANUFACTURER’S/DEVICE ID REGISTER

(Read Only):

D15 D14 D13 D12 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0

10000001000000XX

D0–D1: Undefined. TRI-STATE will be output on SI/0.
D2-D4: Always set LOW.

will stop responding as described. These test modes are to
be used for National Semiconductor production testing only.
See Section 1.2 Serial Bus Interface for a complete discus­sion.

D5–D15: Temperature Data. One LSB = 0.25˚C. Two’s
complement format.

D5–D15: Manufacturer’s ID Data. This register is accessed
whenever the LM70 is in shutdown mode.

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2.0 Serial Bus Timing Diagrams

LM70

a) Reading Continuous Conversion - Single Eight-Bit Frame

10122314

b) Reading Continuous Conversion - Two Eight-Bit Frames

c) Writing Shutdown Control

FIGURE 7. Timing Diagrams

10122315

10122318

3.0 Application Hints

To get the expected results when measuring temperature
with an integrated circuit temperature sensor like the LM70,
it is important to understand that the sensor measures its
own die temperature. For the LM70, the best thermal path
between the die and the outside world is through the LM70’s
pins. In the MSOP-8 package the ground pin is connected to
the back side of the LM70 die and thus has the most effect
on the die temperature. Although the other pins will also
have some effect on the LM70die temperature and therefore
should not be discounted. The LM70 will provide an accurate
measurement of the temperature of the printed circuit board
on which it is mounted, because the pins represent a good
thermal path to the die. A less efficient thermal path exists

between the plastic package and the LM70 die. If the ambi­ent air temperature is significantly different from the printed
circuit board temperature, it will have a small effect on the
measured temperature.

In probe-type applications, the LM70 can be mounted inside
a sealed-end metal tube, and can then be dipped into a bath
or screwed into a threaded hole in a tank. As with any IC, the
LM70 and accompanying wiring and circuits must be kept
insulated and dry, to avoid leakage and corrosion. This is
especially true if the circuit may operate at cold temperatures
where condensation can occur. Printed-circuit coatings and
varnishes such as Humiseal and epoxy paints or dips are
often used to insure that moisture cannot corrode the LM70
or its connections.

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4.0 Typical Applications

LM70

10122320

FIGURE 8. Temperature monitor using Intel 196 processor

FIGURE 9. LM70 digital input control using micro-controller’s general purpose I/O.

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10122319

Physical Dimensions inches (millimeters) unless otherwise noted

LM70

8-Lead Molded Mini Small Outline Package (MSOP)

(JEDEC REGISTRATION NUMBER M0-187)

Order Number LM70CIMM-3, LM70CIMMX-3, LM70CIMM-5 or LM70CIMMX-5

NS Package Number MUA08A

8-Lead Molded Leadless Leadframe Package

Order Number LM70CILD-3, LM70CILDX-3, LM70CILD-5 or LM70CILDX-5

NS Package Number LDA08A

www.national.com13

Notes

10-Bit plus Sign Digital Temperature Sensor

™

National does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and National reserves
the right at any time without notice to change said circuitry and specifications.

For the most current product information visit us at www.national.com.

LM70 SPI/MICROWIRE

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. As used herein:

1. Life support devices or systems are devices or systems
which, (a) are intended for surgical implant into the body, or
(b) support or sustain life, and whose failure to perform when
properly used in accordance with instructions for use
provided in the labeling, can be reasonably expected to result
in a significant injury to the user.

BANNED SUBSTANCE COMPLIANCE

National Semiconductor certifies that the products and packing materials meet the provisions of the Customer Products Stewardship
Specification (CSP-9-111C2) and the Banned Substances and Materials of Interest Specification (CSP-9-111S2) and contain no ‘‘Banned
Substances’’ as defined in CSP-9-111S2.

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Support Center

Email: [e-mail]
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2. A critical component is any component of a life support
device or system whose failure to perform can be reasonably
expected to cause the failure of the life support device or
system, or to affect its safety or effectiveness.

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Support Center

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