LM74CIMX-5/NOPB - NATIONAL SEMICONDUCTOR

LM74

LM74 SPI/ MICROWIRE 12-Bit Plus Sign Temperature Sensor

Literature Number: SNIS107J

LM74

March 1, 2011

SPI/MICROWIRE™ 12-Bit Plus Sign Temperature Sensor

General Description

The LM74 is a temperature sensor, Delta-Sigma analog-to-

digital converter with an SPI and MICROWIRE compatible

interface. The host can query the LM74 at any time to read

temperature. A shutdown mode decreases power consump-

tion to less than 10 μA. This mode is useful in systems where

low average power consumption is critical.

The LM74 has 12-bit plus sign temperature resolution

(0.0625°C per LSB) while operating over a temperature range

of −55°C to +150°C.

The LM74's 3.0V 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 pro-

tection applications in hard disk drives, printers, electronic

test equipment, and office electronics. The LM74 is available

in the SO-8 package as well as an 5-Bump micro SMD pack-

age.

Applications

■System Thermal Management

■Personal Computers

■Disk Drives

■Office Electronics

■Electronic Test Equipment

Features

■0.0625°C temperature resolution.

■Shutdown mode conserves power between temperature

reading

■SPI and MICROWIRE Bus interface

■5-Bump micro SMD package saves space

Key Specifications

■ Supply Voltage 3.0V or 2.65V to

5.5V

■ Supply Current operating 265μA (typ)

520μA (max)

shutdown 3μA (typ)

■ Temperature

Accuracy −10°C to 65°C ±1.25°C(max)

−25°C to 110°C ±2.1°C(max)

−55°C to 125°C ±3°C(max)

Simplified Block Diagram

10090901

TRI-STATE® is a registered trademark of National Semiconductor Corporation.

LM74 SPI/MICROWIRE 12-Bit Plus Sign Temperature Sensor

Connection Diagrams

SO-8

10090902

TOP VIEW

NS Package Number M08A

5-Bump micro SMD

10090924

Note:

- Pin numbers are referenced to the package marking text orientation. Pin 1

is designated by the square.

- Reference JEDEC Registration MO-211, variation BC

- The top 4 characters designate the date code. The bottom 3 characters des-

ignate the device type (see ordering information).

TOP VIEW

NS Package Number BPD05MPB and TPD05QSA

Ordering Information

Order Number Package

Marking

NS Package

Number Supply Voltage Transport Media

LM74CIM-3 LM74CIM-3 SO-8, M08A 3.0V to 3.6V 95 Units in Rail

LM74CIMX-3 LM74CIM-3 SO-8, M08A 3.0V to 3.6V 2500 Units in Tape and Reel

LM74CIM-5 LM74CIM-5 SO-8, M08A 4.5V to 5.5V 95 Units in Rail

LM74CIMX-5 LM74CIM-5 SO-8, M08A 4.5V to 5.5V 2500 Units in Tape and Reel

LM74CITP-3 T10

micro SMD, Thin

Package,

TPD05QSA

2.65V to 3.6V 250 Units in Tape and Reel

LM74CITPX-3 T10

micro SMD, Thin

Package,

TPD05QSA

2.65V to 3.6V 3000 Units in Tape and Reel

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LM74

Pin Descriptions

Label SO-8

Pin #

micro

SMD

Pin #

Function Typical Connection

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

line. Schmitt trigger input. From and to Controller

SC 2 5 Slave Clock - Serial bus clock Schmitt trigger input

line. From Controller

NC 3 No Connection No Connection

GND 4 4 Power Supply Ground Ground

NC 5 No Connection No Connection

NC 6 No Connection No Connection

CS 7 3 Chip Select input. From Controller

V+8 2 Positive Supply Voltage Input

DC Voltage from 3.0V to 5.5V for the LM74CIM

and 2.65V to 5.5V for the LM74CIBP and

LM74CITP. Bypass with a 0.1 μF ceramic

capacitor.

Typical Application

10090903

FIGURE 1. COP Microcontroller Interface

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LM74

Absolute Maximum Ratings (Note 1)

Supply Voltage −0.3V to 6.0V

Voltage at any Pin −0.3V to V+ + 0.3V

Input Current at any Pin (Note 2) 5 mA

Package Input Current (Note 2) 20 mA

Storage Temperature −65°C to +150°C

ESD Susceptibility (Note 4)

Human Body Model

LM74CIBP and LM74CITP, pin A2

(SC)

1900V

LM74CIM,LM74CIBP, and

LM74CITP all other pins

2000V

Machine Model 200V

Soldering process must comply with National's Reflow

Temperature Profile specifications. Refer to

www.national.com/packaging. (Note 3)

Operating Ratings

Specified Temperature Range TMIN to TMAX

(Note 5)

LM74CIBP and LM74CITP

LM74CIM

−40°C to +125°C

−55°C to +150°C

Supply Voltage Range (+VS)

LM74CIBP and LM74CITP +2.65V to +5.5V

LM74CIM +3.0V to +5.5V

Temperature-to-Digital Converter Characteristics

Unless otherwise noted, these specifications apply for V+ = 2.65V to 3.6V for the LM74CIBP -3, LM74CITP-3, V+ = 3.0V to 3.6V

for the LM74CIM -3 and V+ = 4.5V to 5.5V for the LM74 -5 (Note 6). Boldface limits apply for TA = TJ = TMIN to TMAX; all other

limits TA = TJ=+25°C, unless otherwise noted.

Parameter Conditions

Typical

(Note 7)

LM74-5

Limits

(Note 8)

LM74-3

Limits

(Note 8)

Units

(Limit)

Temperature Error (Note 6) TA = −10°C to +65°C ±1.25 ±1.25 °C (max)

TA = −25°C to +110°C ±2.1 +2.65/−2.15 °C (max)

TA = −40°C to +85°C +2.65/−1.65 ±2.15 °C (max)

TA = −40°C to +110°C +2.65/

−2.0

+2.65/−2.15 °C (max)

TA = −55°C to +125°C ±3.0 ±3.5 °C (max)

TA = −55°C to +150°C ±5.0 ±5.0 °C (max)

Resolution 13 Bits

Temperature

Conversion Time

SO-8 (Note 9) 280 425 425 ms (max)

micro SMD (Note 9) 611 925 925 ms (max)

Quiescent Current SO-8 Serial Bus Inactive 310 520 520 μA (max)

micro SMD 265 470 470 μA (max)

SO-8 Serial Bus Active 310 μA

micro SMD 310 μA

SO-8 Shutdown Mode,

V+ = 3.3V

7 μA

micro SMD 3 μA

SO-8 Shutdown Mode,

V+ = 5V

8 μA

micro SMD 4 μA

Logic Electrical Characteristics

DIGITAL DC CHARACTERISTICS

Unless otherwise noted, these specifications apply for V+ = 2.65V to 3.6V for the LM74CIBP -3, LM74CITP-3, V+ = 3.0V to 3.6V

for the LM74CIM -3 and V+ = 4.5V to 5.5V for the LM74 -5 (Note 6). Boldface limits apply for TA = TJ = TMIN to TMAX; all other

limits TA = TJ=+25°C, unless otherwise noted.

Symbol Parameter Conditions Typical

(Note 7)

Limits

(Note 8)

Units

(Limit)

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

V+ + 0.3 V (max)

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

V+ × 0.3 V (max)

Input Hysteresis Voltage V+ = 3.0V to 3.6V 0.8 0.35 V (min)

V+ = 4.5V to 5.5V 0.8 0.33 V (min)

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LM74

Symbol Parameter Conditions Typical

(Note 7)

Limits

(Note 8)

Units

(Limit)

IIN(1) Logical “1” Input Current VIN = V+0.005 3.0 μA (max)

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

CIN All Digital Inputs 20 pF

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

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

IO_TRI-STATE TRI-STATE Output Leakage

Current

VO = GND

VO = V+

−1

μA (min)

μA

(max)

SERIAL BUS DIGITAL SWITCHING CHARACTERISTICS

Unless otherwise noted, these specifications apply for V+ = 2.65V to 3.6V for the LM74CIBP -3, LM74CITP-3, V+ = 3.0V to 3.6V

for the LM74CIM -3 and V+ = 4.5V to 5.5V for the LM74 -5 (Note 6); CL (load capacitance) on output lines = 100 pF unless otherwise

specified. Boldface limits apply for TA = TJ = TMIN to TMAX; all other limits TA = TJ = +25°C, unless otherwise noted.

Symbol Parameter Conditions Typical

(Note 7)

Limits

(Note 8)

Units

(Limit)

t1SC (Clock) Period 0.16

μs (min)

(max)

t2CS Low to SC (Clock) High Set-Up Time 100 ns (min)

t3CS Low to Data Out (SO) Delay 70 ns (max)

t4SC (Clock) Low to Data Out (SO) Delay 100 ns (max)

t5CS High to Data Out (SO) TRI-STATE 200 ns (max)

t6SC (Clock) High to Data In (SI) Hold Time 50 ns (min)

t7Data In (SI) Set-Up Time to SC (Clock) High 30 ns (min)

10090904

FIGURE 2. Data Output Timing Diagram

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LM74

10090905

FIGURE 3. TRI-STATE Data Output Timing Diagram

10090906

FIGURE 4. Data Input Timing Diagram

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 (VI) at any pin exceeds the power supplies (VI < GND or VI > +VS) the current at that pin should be limited to 5 mA. The 20 mA

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: Reflow temperature profiles are different for lead-free and non-lead-free packages.

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 LM74 will be reduced when operating at elevated temperatures. LM74 θJA (thermal resistance, junction-to-ambient) when

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

Device Number NS Package

Number

Thermal

Resistance (θJA)

LM74CIM M08A 160°C/W

LM74CIBP BPD05MPB 250°C/W

LM74CITP TPD05QSA 250°C/W

Note 6: All SOP (LM74CIM) parts will function over the V+ supply voltage range of 3V to 5.5V. All micro SMD (LM74SIBP and LM75CITP) parts will function over

the V+ supply voltage range of 2.65V to 5.5V. The SOP (LM74CIM) parts are tested and specified for rated temperature error at their nominal supply voltage for

temperature ranges of −10°C to +65°C, −55°C to +125°C and −55°C to +150°C. For the SOP (LM74CIM) parts, the temperature error specifications for temperature

ranges of −40°C to +85°C, −25°C to +110°C, and −40°C to +110°C include error induced by power supply variation of ±5% from the nominal value. For the

LM74CIM (SOP) parts, the temperature error will increase by ±0.3°C for a power supply voltage (V+) variation of ±10% from the nominal value.

For the LM74CIBP-3 and LM74CITP-3 (micro SMD) parts all accuracies are guaranteed over the supply range of 2.65V to 3.6V, except for the temperature ranges

of -55°C to 125°C and −55°C to +150°C where the accuracy applies for the nominal supply voltage of 3.3V. For the LM74CIBP-5 and LM74CITP-5 (micro SMD)

parts all accuracies are guranteed over the supply range of 4.75V to 5.25V, except for the temperature ranges of -55°C to 125°C and −55°C to +150°C where

the accuracy applies for the nominal supply voltage of 5.0V. For the LM74CIBP and LM74CITP over -55°C to 125°C and −55°C to +150°C, a power supply

variation of ±10% will degrade the accuracy by ±0.3°C.

Note 7: Typicals are at TA = 25°C and represent most likely parametric norm.

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 LM74 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.

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LM74

Electrical Characteristics

10090908

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

TRI-STATE Test Circuit

10090907

FIGURE 6.

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LM74

Typical Performance Characteristics

Average Power-On Reset Voltage vs Temperature

10090923

Static Supply Current vs Temperature (SO-8)

10090921

Static Supply Current vs Temperature (micro SMD)

10090925

Temperature Error (SO-8)

10090922

1.0 Functional Description

The LM74 temperature sensor incorporates a band-gap type

temperature sensor and 12-bit plus sign ΔΣ ADC (Delta-Sig-

ma Analog-to-Digital Converter). Compatibility of the LM74'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/Device ID

uct.

1.1 POWER UP AND POWER DOWN

When the supply voltage is less than about 1.6V (typical), the

LM74 is considered powered down. The LM74 always powers

up in a known state. When the supply voltage rises above

1.6V (typical), an internal Power-On Reset (POR) occurs and

the temperature register will then contain a value of 1111

1111 0000 00XX, where XX indicates undefined values. See

Section 1.5.2 for a diagram of the Temperature Regisiter con-

tents after POR but before completion of the first temperature

conversion.

The LM74 power-up default condition is continuous conver-

sion mode. After completion of the first full temperature con-

version, the register will contain temperature measurement

data in bits D15 (the temperature data MSB) through D3 (the

temperature data LSB). Bit D2 will be fixed high; bits D1 and

D0 are undefined. See Section 1.5.3 for a diagram of the

Temperature Regisiter contents after the first complete tem-

perature conversion. Note that bit D2 represents a complete

conversion flag. During POR it is low and, after the first tem-

perature conversion is complete, it goes high. This bit can be

polled to indicate when the POR data in the Temperature

After the first conversion, and any subsequent conversions,

the value in the temperature register does not change until

the completion of the next conversion, at which time the tem-

perature register is updated with the latest temperature value.

1.2 SERIAL BUS INTERFACE

The LM74 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 com-

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LM74

munication 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 TRI-STATE®. Communication

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,

twelve temperature bits and 1 high bit) 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 LM74 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 pe-

riods. CS can remain low for 32 SC cycles. The LM74 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 LM74 out of shutdown. The following codes

should only be transmitted to the LM74:

•00 hex

•01 hex

•03 hex

•07 hex

•0F hex

•1F hex

•3F hex

•7F hex

•FF hex

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

are used by National Semiconductor to thoroughly test the

function of the LM74 during production testing. Only eight bits

have been defined above since only the last eight transmitted

are detected by the LM74, before CS is taken HIGH.

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 one complete temperature conversion period will

have to pass before the LM74 Temperature register will con-

tain the new temperature data. Until then, it will contain a

"stale" temperature (the data that was in the register before

going into shutdown mode).

1.3 TEMPERATURE DATA FORMAT

Temperature data is represented by a 13-bit, two's comple-

ment word with an LSB (Least Significant Bit) equal to 0.0625°

Temperature Digital Output

Binary Hex

+150°C 0100 1011 0000 0111 4B 07h

+125°C 0011 1110 1000 0111 3E 87h

+25°C 0000 1100 1000 0111 0C 87h

+0.0625°C 0000 0000 0000 1111 00 0Fh

0°C 0000 0000 0000 0111 00 07h

−0.0625°C 1111 1111 1111 1111 FF FFh

−25°C 1111 0011 1000 0111 F3 87h

−55°C 1110 0100 1000 0111 E4 87h

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 sig-

nificant 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 overtem-

perature 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 LM74 as

shown in Figure 7c. The serial bus is still active when the

LM74 is in shutdown. Current draw drops to less than 10 μA

between serial communications. When in shutdown mode the

LM74 always will output 1000 0000 0000 00XX. This is the

manufacturer's/Device ID information. The first 5-bits of the

field (1000 0XXX) are reserved for manufacturer's ID. As

mentioned in Section 1.2, writing a zero to the LM74 config-

uration register will take it out of shutdown mode and place it

in conversion mode. In other words, any valid code listed in

Section 1.2 other than XX FF will put it in conversion mode.

After leaving shutdown, but before the first temperature con-

version is complete, the temperature register will contain the

last measured temperature which resided in the temperature

of the first conversion, the temperature register will be updat-

ed with the new temperature data.

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LM74

1.5 INTERNAL REGISTER STRUCTURE

The LM74 has three registers, the temperature register, the

configuration register and the manufacturer's/device identifi-

cation register. The temperature and manufacturer's/device

identification registers are read only. The configuration regis-

ter 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

X X X X X X X X Shutdown

D0–D15 set to XX FF hex enables shutdown mode.

D0–D15 set to 00 00 hex sets Continuous conversion mode.

Note: setting D0-D15 to any other values may place the LM74 into a manufacturer's test mode, upon which the LM74 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.

1.5.2 Temperature Register (after power-up, before first complete temperature conversion)

(Read Only):

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

11111111000000XX

D0–D1: Undefined. TRI-STATE will be output on SI/0.

D2–D15: Power-on Reset (POR) values.

1.5.3 Temperature Register (after completion of first temperature conversion)

(Read Only):

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

MSB Bit 11 Bit 10 Bit 9 Bit 8 Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 LSB 1 X X

D0–D1: Undefined. TRI-STATE will be output on SI/0.

D2: High.

D3–D15: Temperature Data. One LSB = 0.0625°C. Two's complement format.

1.5.4 Manufacturer's Device ID Register

(Read Only):

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

10000000000000XX

D0–D1: Undefined. TRI-STATE will be output on SI/0.

D2–D15: Manufacturer's/Device ID Data. This register is accessed whenever the LM74 is in shutdown mode.

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LM74

2.0 Serial Bus Timing Diagrams

10090914

a) Reading Continuous Conversion - Single Eight-Bit Frame

10090915

b) Reading Continuous Conversion - Two Eight-Bit Frames

10090918

c) Writing Shutdown Control

FIGURE 7. Timing Diagrams

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LM74

3.0 Application Hints

To get the expected results when measuring temperature with

an integrated circuit temperature sensor like the LM74, it is

important to understand that the sensor measures its own die

temperature. For the LM74, the best thermal path between

the die and the outside world is through the LM74's pins. In

the SO-8 package all the pins on the LM74 will have an equal

effect on the die temperature. Because the pins represent a

good thermal path to the LM74 die, the LM74 will provide an

accurate measurement of the temperature of the printed cir-

cuit board on which it is mounted. There is a less efficient

thermal path between the plastic package and the LM74 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 LM74 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

LM74 and accompanying wiring and circuits must be kept in-

sulated 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 of-

ten used to insure that moisture cannot corrode the LM74 or

its connections.

3.1 micro SMD LIGHT SENSITIVITY

The LM74 in the micro SMD package should not be exposed

to ultraviolet light. The micro SMD package does not com-

pletely encapsulate the LM74 die in epoxy. Exposing the

LM74 micro SMD package to bright sunlight will not immedi-

atly cause a change in the output reading. Our experiments

show that directly exposing the circuit side (bump side) of the

die to high intensity (≥ 1mW/cm2) ultraviolet light, centered at

a wavelength of 254nm, for greater than 20 minutes will de-

program the EEPROM cells in the LM74. Since the EEPROM

is used for storing calibration coefficients, the LM74 will func-

tion but the temperature accuracy will no longer be as speci-

fied. Light can penetrate through the side of the package as

well, so exposure to ultra violet radiation is not recommended

even after mounting.

4.0 Typical Applications

10090920

FIGURE 8. Temperature monitor using Intel 196 processor

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LM74

10090919

FIGURE 9. LM74 digital input control using micro-controller's general purpose I/O.

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LM74

Physical Dimensions inches (millimeters) unless otherwise noted

8-Lead Molded Small Outline Package

Order Number LM74CIM-3, LM74CIMX-3, LM74CIM-5 or LM74CIMX-5

NS Package Number M08A

5-Bump micro SMD Ball Grid Array Thick Package

Order Number LM74CIBP-3,LM74CIBPX-3, LM74CIBP-5, LM74CIBPX-5

NS Package Number BPD05MPB

The following dimensions apply to the BPD05MPB package

shown above: X1=1565µm ±30µm, X2=1615µm ±30µm, X3=850µm ±50µm.

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LM74

5-Bump micro SMD Ball Grid Array Thin Package

Order Number LM74CITP-3,LM74CITPX-3, LM74CITP-5, LM74CITPX-5

NS Package Number TPD05QSA

The following dimensions apply to the TPD05QSA package

shown above: X1=1590µm ±30µm, X2=1641µm ±30µm, X3=500µm ±75µm.

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LM74

Notes

LM74 SPI/MICROWIRE 12-Bit Plus Sign Temperature Sensor

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