LM74CITPX-5 [NSC]
SPI/MICROWIRE⑩ 12-Bit Plus Sign Temperature Sensor; SPI / MICROWIRE⑩ 12位+符号位温度传感器
| 型号： | LM74CITPX-5 |
| 厂家： | 
National Semiconductor |
| 描述： | SPI/MICROWIRE⑩ 12-Bit Plus Sign Temperature Sensor |
| 文件： | 总15页 (文件大小：707K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
May 2005
LM74
™
SPI/MICROWIRE 12-Bit Plus Sign Temperature Sensor
General Description
The LM74 is a temperature sensor, Delta-Sigma analog-to-
n Electronic Test Equipment
Features
digital converter with an SPI and MICROWIRE compatible
n 0.0625˚C temperature resolution.
n Shutdown mode conserves power between temperature
reading
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.
n SPI and MICROWIRE Bus interface
n 5-Bump micro SMD package saves space
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.
Key Specifications
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 protection applications in hard disk drives, printers, elec-
tronic test equipment, and office electronics. The LM74 is
available in the SO-8 package as well as an 5-Bump micro
SMD package.
j
Supply Voltage
3.0V or 2.65V to
5.5V
j
Supply Current
operating
shutdown
265µA (typ)
520µA (max)
3µA (typ)
j
Temperature
Accuracy
−10˚C to 65˚C
−25˚C to 110˚C
−55˚C to 125˚C
1.25˚C(max)
2.1˚C(max)
3˚C(max)
Applications
n System Thermal Management
n Personal Computers
n Disk Drives
n Office Electronics
Simplified Block Diagram
10090901
MICROWIRE® is a registered trademark of National Semiconductor Corporation.
TRI-STATE® is a registered trademark of National Semiconductor Corporation.
© 2005 National Semiconductor Corporation
DS100909
www.national.com
Connection Diagrams
SO-8
5-Bump micro SMD
10090902
TOP VIEW
NS Package Number M08A
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
designate the device type (see ordering information).
TOP VIEW
NS Package Number BPD05MPB and TPD05QSA
Ordering Information
Package
Order Number
NS Package
Number
SO-8, M08A
Supply Voltage
Transport Media
95 Units in Rail
Marking
LM74CIM-3
LM74CIMX-3
LM74CIM-5
LM74CIMX-5
LM74CIBP-3
LM74CIM-3
LM74CIM-3
LM74CIM-5
LM74CIM-5
T8
3.0V to 3.6V
3.0V to 3.6V
4.5V to 5.5V
4.5V to 5.5V
2.65V to 3.6V
SO-8, M08A
SO-8, M08A
SO-8, M08A
micro SMD, Thick
Package,
2500 Units in Tape and Reel
95 Units in Rail
2500 Units in Tape and Reel
250 Units in Tape and Reel
BPD05MPB
micro SMD, Thick
Package,
LM74CIBPX-3
LM74CIBP-5
LM74CIBPX-5
LM74CITP-3
LM74CITPX-3
LM74CITP-5
LM74CITPX-5
T8
T9
2.65V to 3.6V
4.5V to 5.5V
4.5V to 5.5V
2.65V to 3.6V
2.65V to 3.6V
4.5V to 5.5V
4.5V to 5.5V
3000 Units in Tape and Reel
250 Units in Tape and Reel
3000 Units in Tape and Reel
250 Units in Tape and Reel
3000 Units in Tape and Reel
250 Units in Tape and Reel
3000 Units in Tape and Reel
BPD05MPB
micro SMD, Thick
Package,
BPD05MPB
micro SMD, Thick
Package,
T9
BPD05MPB
micro SMD, Thin
Package,
T10
T10
T11
T11
TPD05QSA
micro SMD, Thin
Package,
TPD05QSA
micro SMD, Thin
Package,
TPD05QSA
micro SMD, Thin
Package,
TPD05QSA
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2
Pin Descriptions
Label
SO-8
micro
SMD
Function
Typical Connection
#
Pin
#
Pin
SI/O
1
1
Slave Input/Output - Serial bus bi-directional data
line. Schmitt trigger input.
From and to Controller
SC
2
5
4
Slave Clock - Serial bus clock Schmitt trigger input From Controller
line.
NC
GND
NC
NC
CS
V+
3
4
5
6
7
8
No Connection
No Connection
Power Supply Ground
No Connection
Ground
No Connection
No Connection
No Connection
3
2
Chip Select input.
Positive Supply Voltage Input
From Controller
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
3
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Absolute Maximum Ratings (Note 1)
Soldering process must comply with National’s Reflow
Temperature Profile specifications. Refer to
www.national.com/packaging. (Note 3)
Supply Voltage
−0.3V to 6.0V
−0.3V to V+ + 0.3V
5 mA
Voltage at any Pin
Input Current at any Pin (Note 2)
Package Input Current (Note 2)
Storage Temperature
ESD Susceptibility (Note 4)
Human Body Model
Operating Ratings
20 mA
−65˚C to +150˚C
Specified Temperature Range
TMIN to TMAX
(Note 5)
LM74CIBP and LM74CITP
LM74CIM
−40˚C to +125˚C
−55˚C to +150˚C
LM74CIBP and LM74CITP, pin
A2 (SC)
1900V
2000V
200V
Supply Voltage Range (+VS)
LM74CIBP and LM74CITP
LM74CIM
+2.65V to +5.5V
+3.0V to +5.5V
LM74CIM,LM74CIBP, and
LM74CITP all other pins
Machine Model
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.
;
Typical
(Note 7)
LM74-5
Limits
(Note 8)
1.25
LM74-3
Limits
(Note 8)
1.25
Units
(Limit)
Parameter
Conditions
Temperature Error (Note 6)
TA = −10˚C to +65˚C
TA = −25˚C to +110˚C
TA = −40˚C to +85˚C
TA = −40˚C to +110˚C
˚C (max)
˚C (max)
˚C (max)
˚C (max)
2.1
+2.65/−2.15
2.15
+2.65/−1.65
+2.65/
−2.0
+2.65/−2.15
TA = −55˚C to +125˚C
TA = −55˚C to +150˚C
3.0
3.5
5.0
˚C (max)
˚C (max)
Bits
5.0
Resolution
13
280
611
310
265
310
310
7
Temperature
Conversion Time
SO-8 (Note 9)
micro SMD (Note 9)
SO-8 Serial Bus Inactive
micro SMD
SO-8 Serial Bus Active
micro SMD
SO-8 Shutdown Mode,
V+ = 3.3V
425
925
520
470
425
925
520
470
ms (max)
ms (max)
µA (max)
µA (max)
µA
Quiescent Current
µA
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.
Typical
(Note 7)
Limits
(Note 8)
V+ x 0.7
V+ + 0.3
−0.3
Units
(Limit)
Symbol
VIN(1)
Parameter
Conditions
Logical “1” Input Voltage
V (min)
V (max)
V (min)
V (max)
V (min)
V (min)
µA (max)
VIN(0)
Logical “0” Input Voltage
Input Hysteresis Voltage
Logical “1” Input Current
V+ x 0.3
V+ = 3.0V to 3.6V
V+ = 4.5V to 5.5V
VIN = V+
0.8
0.8
0.35
0.33
IIN(1)
0.005
3.0
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4
Logic Electrical Characteristics (Continued)
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.
Typical
(Note 7)
−0.005
20
Limits
(Note 8)
−3.0
Units
(Limit)
µA (min)
pF
Symbol
IIN(0)
Parameter
Conditions
VIN = 0V
Logical “0” Input Current
All Digital Inputs
CIN
VOH
High Level Output Voltage
Low Level Output Voltage
TRI-STATE Output Leakage
Current
IOH = −400 µA
IOL = +2 mA
VO = GND
VO = V+
2.4
0.4
−1
V (min)
V (max)
µA (min)
µA
VOL
IO_TRI-STATE
+1
(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.
=
Typical
(Note 7)
Limits
(Note 8)
0.16
DC
Units
(Limit)
Symbol
t1
Parameter
Conditions
SC (Clock) Period
µs (min)
(max)
t2
t3
t4
t5
t6
t7
CS Low to SC (Clock) High Set-Up Time
CS Low to Data Out (SO) Delay
100
ns (min)
ns (max)
ns (max)
ns (max)
ns (min)
ns (min)
70
SC (Clock) Low to Data Out (SO) Delay
CS High to Data Out (SO) TRI-STATE
SC (Clock) High to Data In (SI) Hold Time
Data In (SI) Set-Up Time to SC (Clock) High
100
200
50
30
10090904
FIGURE 2. Data Output Timing Diagram
5
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Logic Electrical Characteristics (Continued)
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.
<
>
+V ) the current at that pin should be limited to 5 mA. The 20 mA
Note 2: When the input voltage (V ) at any pin exceeds the power supplies (V
GND or V
I
I
I
S
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 θ (thermal resistance, junction-to-ambient) when
JA
attached to a printed circuit board with 2 oz. foil is summarized in the table below:
NS Package
Number
Thermal
Resistance (θJA
160˚C/W
Device Number
)
LM74CIM
LM74CIBP
LM74CITP
M08A
BPD05MPB
TPD05QSA
250˚C/W
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.
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6
Logic Electrical Characteristics (Continued)
Note 7: Typicals are at T = 25˚C and represent most likely parametric norm.
A
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.
Electrical Characteristics
10090908
FIGURE 5. Temperature-to-Digital Transfer Function (Non-linear scale for clarity)
TRI-STATE Test Circuit
10090907
FIGURE 6.
7
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Typical Performance Characteristics
Average Power-On Reset Voltage vs Temperature
Static Supply Current vs Temperature (SO-8)
10090923
10090921
Temperature Error (SO-8)
Static Supply Current vs Temperature (micro SMD)
10090925
10090922
conversion, the register will contain temperature measure-
ment 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
temperature conversion. Note that bit D2 represents a com-
plete conversion flag. During POR it is low and, after the first
temperature conversion is complete, it goes high. This bit
can be polled to indicate when the POR data in the Tem-
perature Register has been replaced with valid temperature
data.
1.0 Functional Description
The LM74 temperature sensor incorporates a band-gap type
temperature sensor and 12-bit plus sign ∆Σ ADC (Delta-
Sigma Analog-to-Digital Converter). Compatibility of the
LM74’s three wire serial interface with SPI and MICROWIRE
allows simple communications with common microcontrol-
lers and processors. Shutdown mode can be used to opti-
mize current drain for different applications. A Manufacture’s/
Device ID register identifies the LM74 as National
Semiconductor product.
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
temperature register is updated with the latest temperature
value.
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 contents after POR but before completion of the
first temperature conversion.
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-
The LM74 power-up default condition is continuous conver-
sion mode. After completion of the first full temperature
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8
Note that one complete temperature conversion period will
have to pass before the LM74 Temperature register will
contain the new temperature data. Until then, it will contain a
"stale" temperature (the data that was in the register before
going into shutdown mode).
1.0 Functional Description (Continued)
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®. Communica-
tion 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 transmit-
ted 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.
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˚C:
Temperature
Digital Output
Binary
Hex
+150˚C
+125˚C
+25˚C
0100 1011 0000 0111
0011 1110 1000 0111
0000 1100 1000 0111
0000 0000 0000 1111
0000 0000 0000 0111
1111 1111 1111 1111
1111 0011 1000 0111
1110 0100 1000 0111
4B 07h
3E 87h
0C 87h
00 0Fh
00 07h
FF FFh
F3 87h
E4 87h
+0.0625˚C
0˚C
The receive phase of a communication starts after 16 SC
periods. 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:
−0.0625˚C
−25˚C
−55˚C
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 neces-
sary 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 im-
mediately take action to remedy the excessive tempera-
tures.
•
•
•
•
•
•
•
•
•
00 hex
01 hex
03 hex
07 hex
0F hex
1F hex
3F hex
7F hex
FF hex
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 con-
figuration 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 tempera-
ture conversion is complete, the temperature register will
contain the last measured temperature which resided in the
temperature register before entering shutdown mode. After
the completion of the first conversion, the temperature reg-
ister will be updated with the new temperature data.
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 trans-
mitted 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.
9
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1.0 Functional Description (Continued)
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 reg-
ister 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
1
1
1
1
1
1
1
1
0
0
0
0
0
0
X
X
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
1
0
0
0
0
0
0
0
0
0
0
0
0
0
X
X
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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10
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
11
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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 LM74
or its connections.
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 circuit 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.
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 imme-
diatly cause a change in the output reading. Our experi-
ments 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 deprogram the EEPROM cells in the LM74.
Since the EEPROM is used for storing calibration coeffi-
cients, the LM74 will function but the temperature accuracy
will no longer be as specified. Light can penetrate through
the side of the package as well, so exposure to ultra violet
radiation is not recommended even after mounting.
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
insulated and dry, to avoid leakage and corrosion. This is
especially true if the circuit may operate at cold temperatures
4.0 Typical Applications
10090920
FIGURE 8. Temperature monitor using Intel 196 processor
www.national.com
12
4.0 Typical Applications (Continued)
10090919
FIGURE 9. LM74 digital input control using micro-controller’s general purpose I/O.
13
www.national.com
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.
www.national.com
14
Physical Dimensions inches (millimeters) unless otherwise noted (Continued)
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.
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.
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.
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.
BANNED SUBSTANCE COMPLIANCE
National Semiconductor manufactures products and uses packing materials that 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.
National Semiconductor
Americas Customer
Support Center
National Semiconductor
Europe Customer Support Center
Fax: +49 (0) 180-530 85 86
National Semiconductor
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Support Center
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Japan Customer Support Center
Fax: 81-3-5639-7507
Email: new.feedback@nsc.com
Tel: 1-800-272-9959
Email: europe.support@nsc.com
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Français Tel: +33 (0) 1 41 91 8790
Email: ap.support@nsc.com
Email: jpn.feedback@nsc.com
Tel: 81-3-5639-7560
www.national.com
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