LM95172
December 16, 2009
13-Bit to 16-Bit 200°C Digital Temp Sensor with 3-Wire
Interface
General Description
The LM95172EWG is an integrated digital-output tempera-
ture sensor with a Serial Peripheral Interface (SPI) and MI-
CROWIRE™-compatible interface in a 10-pin Cerpack high
temperature ceramic package. It features a very linear Sigma-
Delta Analog-to-Digital Converter (ADC), high accuracy, fast
conversion rates, and extremely low output noise. With an
operating temperature as low as -40°C and optimized accu-
racy from 120°C to 200°C, it is ideal for high-temperature
applications.
The over-temperature alarm output (OVERTEMP) asserts
when the die temperature exceeds a programmed THIGH limit.
The user-programmed TLOW limit creates a temperature-sta-
bilizing hysteresis when the ambient temperature is near the
trip point.
The LM95172EWG can be programmed to operate from 13
bits (0.0625°C per LSB) to 16 bits (0.0078125°C per LSB)
resolution. The LM95172EWG powers up in 35 ms, the
fastest conversion time, with temperature output set at 13-bit
resolution. The resolution may then be changed to 14-, 15- or
16-bits. When in the 13-, 14- or 15-bit resolution mode, the
least significant bit in the 16-bit temperature register toggles
after the completion of each conversion. This bit may be mon-
itored to verify that the conversion is complete.
The high noise immunity of the Serial I/O (SI/O) output makes
the LM95172EWG ideal for use in challenging electromag-
netic environments.
Applications
■Automotive high temperature applications
■Industrial Power Controllers
■Industrial motors, gear boxes
■Geothermal instrumentation
■High Temperature Test Equipment
Features
■LM95172EWG is AEC-Q100 Grade 0 qualified and is
manufactured on an Automotive Grade Flow.
■13-bit (0.0625°C LSB) to 16-bit (0.0078125°C LSB)
temperature resolution
■Wide −40°C to +200°C temperature range
■35 ms best conversion time tracks fast temp changes
■OVERTEMP digital output switches when TDIE > THIGH
■Shutdown mode saves power yet wakes up for one-shot
temperature update
■SPI and MICROWIRE Bus interface
■10-Pin Cerpack high-temperature ceramic package
Key Specifications
■ Analog and Digital Supply Voltage 3.0V to 5.5V
■ Total Supply Current Operating 400 µA (typ)
Shutdown −40°C to +140°C 4 µA (max)
Shutdown −40°C to +175°C 12 µA (max)
Shutdown −40°C to +200°C 28 µA (max)
■ Temperature Accuracy
+175°C to +200°C ±3.0°C (max)
+130°C to +160°C ±1.0°C (max)
+120°C to +130°C ±2.0°C (max)
+160°C to +175°C ±2.0°C (max)
−40°C to +120°C ±3.5°C (max)
■ Temperature Resolution
13-bit mode 0.0625°C/LSB
16-bit mode 0.0078125°C/LSB
■ Conversion Time
13-bit mode 43 ms (max)
16-bit mode 350 ms (max)
Connection Diagram
LM95172EWG Top View
30076602
MICROWIRE™ is a trademark of National Semiconductor Corporation.
TRI-STATE® is a registered trademark of National Semiconductor Corporation.
© 2009 National Semiconductor Corporation 300766 www.national.com
LM95172 13-Bit to 16-Bit 200°C Digital Temp Sensor with 3-Wire Interface
Pin Descriptions
Pin
Number Name Type Description Typical Connection
1 OVERTEMP Output OVERTEMP Alarm Over-temperature Alarm Output, Open-drain. Active
Low on POR. Requires a pull-up resistor to VDD IO.
2 SC Input Serial Clock input Serial clock from the Controller
3 NC N/A No Connect Do not connect to this pin.
4 CS Input Chip Select input Chip Select input for the bus. Low pass filtered.
5 GND Ground Power Supply Ground Ground
6 NC N/A No Connect Do not connect to this pin.
7 SI/O Bidirectio
nal Serial I/O Serial I/O Data line to or from the Controller
8 NC N/A No Connect Do not connect to this pin.
9VDD ANALOG Power Analog Power Supply
Voltage
DC Voltage from 3.0V to 5.5V. Bypass with a 10 nF
ceramic capacitor near the pad to ground.
10 VDD IO Power Digital Power Supply
Voltage
DC Voltage from 3.0V to 5.5V. Bypass with a 10 nF
ceramic capacitor near the pin to ground.
Simplified Block Diagram
30076601
Ordering Information
Order Number NS Package Number Transport Media
LM95172EWG WG10A 54 units in tray
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LM95172
Typical Application
30076603
FIGURE 1. Microcontroller Interface - normal connection
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LM95172
Absolute Maximum Ratings (Note 1)
VDD ANALOG and VDD IO Supply
Voltages −0.2V to 6.0V
Voltage at any Pin −0.2V to (VDD IO + 0.2V)
Input Current at any Pin 5 mA
Storage Temperature −65°C to +175°C
Soldering Information
Infrared or Convection
(20 sec.) 235°C
ESD Susceptibility (Note 7)
Human Body Model
Machine Model
Charged Device Model
2500 V
250 V
1000 V
Operating Ratings
Specified Temperature Range −40°C to +200°C
Analog Supply Voltage Range
VDD ANALOG
+3.0V to +5.5V
Digital Supply Voltage Range
VDD IO
+3.0V to +5.5V
Package Thermal Resistances
Package θJA
10-Lead CERPACK 175°C/W
Temperature-to-Digital Converter Characteristics Unless otherwise noted, these specifications
apply for VDD ANALOG = VDD IO = 3.0V to 3.6V.(Note 8) Boldface limits apply for TA =−40°C to +200°C; all other limits TA = 25°C,
unless otherwise noted.
Parameter Conditions Typical
(Note 3)
LM95172EWG
Limits
(Note 2)
Units
(Limit)
Temperature
Accuracy
(Note 8)
TA = +175°C to +200°C ±3.0
TA = +130°C to +160°C ±1.0
°C (max)
TA = +120°C to +130°C ±2.0
TA = +160°C to +175°C ±2.0
TA = −40°C to +120°C ±3.5
Resolution
Res 1 Bit Res 0 Bit
0 0
13
0.0625
Bits
°C
0 1 14
0.03125
Bits
°C
1 0 15
0.015625
Bits
°C
1 116
0.0078125
Bits
°C
Temperature
Conversion Time
For 13 Bits Resolution 43
ms (max)
For 14 Bits Resolution 87
For 15 Bits Resolution 175
For 16 BIts Resolution 350
Total Quiescent
Current
(Note 9)
Bus Inactive
Continuous Conversion Mode
TA = −40°C to
140°C
400 456
μA (max)
TA = −40°C to
175°C
510
TA = −40°C to
200°C
500 650
Shutdown Mode
TA = −40°C to
140°C
4
TA = −40°C to
175°C
12
TA = −40°C to
200°C
28 75
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LM95172
Logic Electrical Characteristics
Digital DC Characteristics
Unless otherwise noted, these specifications apply for VDD ANALOG = VDD IO = 3.0V to 3.6V. (Note 8). Boldface limits apply for
TA = -40°C to 200°C; all other limits TA = +25°C, unless otherwise noted.
Symbol Parameter Conditions Typical
(Note 3)
Limits
(Note 2)
Units
(Limit)
VIH Logical "1" Input Voltage 0.75×VDD IO V (min)
VIL Logical "0" Input Voltage 0.25×VDD IO V (max)
VHYST Digital Input Hysteresis
VDD IO = 3.0V 0.63 0.42 V (min)
VDD IO = 3.3V 0.79 0.56
VDD IO = 3.6V 0.97 0.72
VDD IO = 4.5V 0.9
VDD IO = 5.0V 1.0
VDD IO = 5.5V 1.1
IIH Logical “1” Input Leakage Current VIN = VDD IO 1μA (max)
IIL Logical “0” Input Current VIN = 0V −1 μA (max)
VOH Output High Voltage IOH = 100 μA (Source) VDD IO − 0.2 V (min)
IOH = 2 mA (Source) VDD IO − 0.45
VOL Output Low Voltage IOL = 100 μA (Sink) 0.2 V (max)
IOL = 2 mA (Sink) 0.45
OVERTEMP Output Saturation Voltage IOL = 2 mA (Sink) 0.45 V(max)
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LM95172
Serial Bus Digital Switching Characteristics
Unless otherwise noted, these specifications apply for VDD ANALOG = VDD IO = 3.0V to 3.6V (Note 8); CL (load capacitance) on output
lines = 100 pF unless otherwise specified. Boldface limits apply for TA = -40°C to 200°C; all other limits TA = +25°C, unless
otherwise noted.
Symbol Parameter Typical
(Note 3)
Limits
(Note 2)
Units
(Limit)
t1SC (Serial Clock) Period 765 ns (min)
t2CS (Chip Select) Low to SC High Set-Up Time (Note 5) 1.25 µs (min)
t3CS Low to SI/O Output Delay (Note 5) 1µs (max)
t4SC Low to SI/O Output Delay 120 ns (max)
t5CS High to Data Out (SI/O) TRI-STATE 220 ns (max)
t6SC High to SI/O Input Hold Time 50 ns (min)
t7SI/O Input to SC High Set-Up Time 30 ns (min)
t8SC Low to CS High Hold Time 50 ns (min)
tTA Data Turn-Around Time: SI/O input (write to LM95172EWG) to output (read from
LM95172EWG)
130 ns (max)
tBUF Bus free time between communications: CS High to CS Low.
(Note 5)
5µs (min)
30076604
FIGURE 2. Data Output Timing Diagram
30076605
FIGURE 3. TRI-STATE Data Output Timing Diagram
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LM95172
30076606
FIGURE 4. Data Input Timing Diagram
30076609
FIGURE 5. tBUF Timing Definition Diagram
30076610
FIGURE 6. tTA Timing Definition Diagram
Note 1: “Absolute Maximum Ratings” indicate limits beyond which damage to the device may occur, including inoperability and degradation of device reliability
and/or performance. Functional operation of the device and/or non-degradation at the Absolute Maximum Ratings or other conditions beyond those indicated in
the Operating Ratings is not implied. The Operating Ratings indicate conditions at which the device is functional and the device should not be operated beyond
such conditions.
Note 2: The Electrical characteristics tables list guaranteed specifications under the listed Operating Ratings except as otherwise modified or specified by the
Electrical Characteristics Conditions and/or Notes. Typical specifications are estimations only and are not guaranteed.
Note 3: Typical values represent most likely parametric norms at specific conditions (Example Vcc; specific temperature) and at the recommended Operating
Conditions at the time of product characterizations and are not guaranteed.
Note 4: Specification is guaranteed by characterization and is not tested in production
Note 5: Specification is guaranteed by design and is not tested in production
Note 6: Invalid. The LM95172EWG will return a "0" if read. If written to, no valid register will be modified.
Note 7: Human body model, 100 pF discharged through a 1.5 kΩ resistor. Machine model, 200 pF discharged directly into each pin. The Charged Device Model
(CDM) is a specified circuit characterizing an ESD event that occurs when a device acquires charge through some triboelectric (frictional) or electrostatic induction
processes and then abruptly touches a grounded object or surface.
Note 8: The LM95172EWG will operate properly over the VDD ANALOG = 3.0V to 5.5V and VDD IO = 3.0V to 5.5V supply voltage ranges.
Note 9: Total Quiescent Current includes the sum of the currents into the VDD ANALOG and the VDD IO pins.
Note 10: This specification is provided only to indicate how often temperature data is updated. The LM95172EWG 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.
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LM95172
TRI-STATE Test Circuit
30076607
FIGURE 7.
1.0 Functional Description
The LM95172EWG temperature sensor incorporates a tem-
perature sensor and a 13-bit to 16-bit ΣΔ ADC (Sigma-Delta
Analog-to-Digital Converter). Compatibility of the
LM95172EWG's three wire serial interface with SPI and MI-
CROWIRE allows simple communications with common mi-
crocontrollers and processors. Shutdown mode can be used
to optimize current drain for different applications. A
Manufacturer's/Device ID register identifies the
LM95172EWG as National Semiconductor product. See Fig-
ure 8 for the Functional Block Diagram.
30076622
FIGURE 8. LM95172EWG Functional Block Diagram
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LM95172
1.1 INITIAL SOFTWARE RESET AND POWER-UP
SEQUENCES AND POWER ON RESET (POR)
1.1.1 Software Reset Sequence
A software reset sequence must be followed, after the initial
VDD ANALOG and VDD IO supply voltages reach their specified
minimum operating voltages, in order to ensure proper oper-
ation of the LM95172EWG.
The software reset sequence is as follows:
1. Allow VDD ANALOG and VDD IO to reach their specified mini-
mum operating voltages, as specified in the Operating Rat-
ings section, and in a manner as specified in section 1.1.2
below.
2. Write a “1” to the Shutdown bit, Bit 15 of the Control/Status
Register, and hold it high for at least the specified maximum
conversion time for the initial default of 13-bits resolution, in
order to ensure that a complete reset operation has occurred.
(See the Temperature Conversion Time specifications within
the Temperature-to-Digital Characteristics section.)
3. Write a “0” to the Shutdown bit to restore the LM95172EWG
to normal mode.
4. Wait for at least the specified maximum conversion time for
the initial default of 13-bits resolution in order to ensure that
accurate data appears in the Temperature Register.
1.1.2 Power-Up Sequence
Warning: In all cases listed below the VDD ANALOGwaveform must not
lag the VDD IOwaveform
A. Linear Power-up
In the case where the VDD ANALOG and VDD IO voltage-vs.-time
function is linear, the specified minimum operating voltage
must be reached in 5 ms or less.
B. Resistor-Capacitor (R-C) Charging Exponential Power-up
In the case where the VDD ANALOG and VDD IO voltage-vs.-time
function is as a typical R-C Charging exponential function the
time constant must be less than or equal to 1.25 ms.
C. Other Power-up Functions
In the case where the VDD ANALOG and VDD IO voltage-vs.-time
characteristic follows another function the following require-
ments must be met:
(1) The specified minimum operating voltage values for
VDD ANALOG and VDD IO must be reached in 5 ms or less.
(2) The slope of the VDD ANALOG and VDD IO power-up curves
must be greater than or equal to 0.7 V/ms at any time before
the specified minimum operating voltage is reached.
(3) The slope of the VDD ANALOG and VDD IO power-up curves
must not allow ringing such that the voltage is allowed to drop
below the specified minimum operating voltage at any time
after the specified minimum operating voltage is reached.
1.1.3 Power On Reset (POR)
After the requirements of section 1.1.1 and 1.1.2 above are
met each register will then contain its defined POR default
value. Any of the following actions may cause register values
to change from their POR value:
1. The master writes different data to any Read/Write (R/W)
bits, or
2. The LM95172EWG is powered down.
The specific POR Value of each register is listed in Section
1.7 under Internal Register Structure.
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LM95172
1.2 ONE SHOT CONVERSION
The LM95172EWG features a one-shot conversion bit, which
is used to initiate a singe conversion and comparison cycle
when the LM95172EWG is in shutdown mode. While the
LM95172EWG is in shutdown mode, writing a "1" to the One-
Shot bit in the Control/Status Register will cause the
LM95172EWG to perform a single temperature conversion
and update the Temperature Register and the affected status
bits. Operating the LM95172EWG in this one-shot mode al-
lows for extremely low average-power comsumption, making
it ideal for low-power applications.
When the One-shot bit is set, the LM95172EWG initiates a
temperature conversion. After this initiation, but before the
completion of the conversion, and resultant register updates,
the LM95172EWG is in a "one-shot" state. During this state,
the Data Available (DAV) flag in the Control/Status Register
is "0" and the Temperature Register contains the value 8000h
(-256°C). All other registers contain the data that was present
before initiating the one-shot conversion. After the tempera-
ture measurement is complete, the DAV flag will be set to "1"
and the temperature register will contain the resultant mea-
sured temperature.
1.3 OVERTEMP OUTPUT
The Over-temperature (OVERTEMP) output is a temperature
switch signal that indicates when the measured temperature
exceeds the THIGH programmed limit. The programmable
THIGH register sets the high temperature limit and the TLOW
register is used to set the hysteresis. The TLOW register also
sets the temperature below which the OVERTEMP output re-
sets. The OVERTEMP output of the LM95172EWG behaves
as a temperature comparator. The following explains the op-
eration of OVERTEMP. Figure 9 illustrates the OVERTEMP
output behavior.
30076621
FIGURE 9. LM95172EWG OVERTEMP vs. Temperature Response Diagram
The OVERTEMP Output will assert when the measured tem-
perature is greater than the THIGH value. OVERTEMP will
reset if any of the following events happen:
1. The temperature falls below the value stored in the TLOW
register, or
2. A "1" is written to the OVERTEMP Reset bit in the Control/
Status Register.
If OVERTEMP is cleared by the master writing a "1" to the
OVERTEMP Reset bit while the measured temperature still
exceeds the THIGH value, OVERTEMP will assert again after
the completion of the next temperature conversion. Placing
the LM95172EWG in shutdown mode or triggering a one-shot
conversion does not cause OVERTEMP to reset.
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LM95172
1.4 COMMUNICATING WITH THE LM95172EWG
The serial interface consists of three lines: CS (Chip Select),
SC (Serial Clock), and the bi-directional SI/O (Serial I/O) data
line. A high-to-low transition of the CS line initiates the com-
munication. The master (processor) always drives the chip
select and the clock. The first 16 clocks shift the temperature
data out of the LM95172EWG on the SI/O line (a temperature
read). Raising the CS at anytime during the communication
will terminate this read operation. Following this temperature
read, the SI/O line becomes an input and a command byte
can be written to the LM95172EWG. This command byte
contains a R/W bit and the address of the register to be com-
municated with next (see Section 1.7 Internal Register Struc-
ture). When writing, the data is latched in after every 8 bits.
The processor must write at least 8 bits in order to latch the
data. If CS is raised before the falling edge of the 8th com-
mand bit, no data will be latched into the command byte. If
CS is raised after the 8th bit, but before the 16th bit, of a write
to a 16-bit data register, only the most significant byte of the
data will be latched. This command-data-command-data se-
quence may be performed as many times as desired.
30076614
FIGURE 10. Reading the Temperature Register
30076616
FIGURE 11. Reading the Temperature Register followed by a read or write from another register (Control/Status, THIGH,
TLOW, or Identification register)
30076615
FIGURE 12. Reading the Temperature Register followed by repeated commands and Data Register accesses (Control/
Status, THIGH, TLOW, or Identification register)
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LM95172
1.5 TEMPERATURE DATA FORMAT
Temperature data is represented by a 13- to 16-bit, two's
complement word with a Least Significant Bit (LSB) equal to
0.0625 °C (13-bits), 0.03125 °C (14-bits), 0.015625 °C (15-
bits) or 0.0078125 °C (16-bits). See Section 1.7.2 for defini-
tion of the bits in the Temperature Register.
13-Bit Resolution. First Bit (D15) is Sign, the last bit (D0) is Toggle and bits D1 and D2 are always 0.
Temperature
13-bit Resolution Digital Output
16-bit Binary All 16 Bits Bits D15 - D3
Hex Hex
+175°C 0101011110000 000 5780 0AF0
0101011110000 001 5781
+150°C 0100101100000 000 4B00 0960
0100101100000 001 4B01
+80°C 0010100000000 000 2800 0500
0010100000000 001 2801
+25°C 0000110010000 000 0C80 0190
0000110010000 001 0C81
+0.0625°C 0000000000001 000 0008 0001
0000000000001 001 0009
0°C 0000000000000 000 0000 0000
0000000000000 001 0001
−0.0625°C 1111111111111 000 FFF8 1FFF
1111111111111 001 FFF9
−40°C 1110110000000 000 EC00 1D80
1110110000000 001 EC01
14-Bit Resolution. First bit (D15) is Sign, the last bit (D0) is Toggle and bit D1 is always 0.
Temperature
14-bit Resolution Digital Output
16-bit Binary All 16 Bits Bits D15 - D2
Hex Hex
+175°C 01010111100000 00 5780 15E0
01010111100000 01 5781
+150°C 01001011000000 00 4B00 12C0
01001011000000 01 4B01
+80°C 00101000000000 00 2800 0A00
00101000000000 01 2801
+25°C 00001100100000 00 0C80 0320
00001100100000 01 0C81
+0.03125°C 00000000000001 00 0004 0001
00000000000001 01 0005
0°C 00000000000000 00 0000 0000
00000000000000 01 0001
−0.03125°C 11111111111111 00 FFFC 3FFF
11111111111111 01 FFFD
−40°C 11101100000000 00 EC00 3B00
11101100000000 01 EC01
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LM95172
15-Bit Resolution. First bit (D15) is Sign and the last bit (D0) is Toggle.
Temperature
15-bit Resolution Digital Output
16-bit Binary All 16 Bits Bits D15 - D1
Hex Hex
+175°C 010101111000000 0 5780 2BC0
010101111000000 1 5781
+150°C 010010110000000 0 4B00 2580
010010110000000 1 4B01
+80°C 001010000000000 0 2800 1400
001010000000000 1 2801
+25°C 000011001000000 0 0C80 0640
000011001000000 1 0C81
+0.015625°C 000000000000001 0 0002 0001
000000000000001 1 0003
0°C 000000000000000 0 0000 0000
000000000000000 1 0001
−0.015625°C 111111111111111 0 FFFE 7FFF
111111111111111 1 FFFF
−40°C 111011000000000 0 EC00 7600
111011000000000 1 EC01
16-Bit Resolution. First bit (D15) is Sign and the last bit (D0) is the LSB.
Temperature
16-bit Resolution Digital Output
16-bit Binary All 16 Bits
Hex
+175°C 0101 0111 1000 0000 5780
+150°C 0100 1011 0000 0000 4B00
+80°C 0010 1000 0000 0000 2800
+25°C 0000 1100 1000 0000 0C80
+0.0078125°C 0000 0000 0000 0001 0001
0°C 0000 0000 0000 0000 0000
−0.0078125°C 1111 1111 1111 1111 FFFF
−40°C 1110 1100 0000 0000 EC00
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.
1.6 SHUTDOWN MODE
Shutdown Mode is enabled by writing a “1” to the Shutdown
Bit, Bit 15 of the Control/Status Register, and holding it high
for at least the specified maximum conversion time at the ex-
isting temperature resolution setting. (see Temperature Con-
version Time specifications under the Temperature-to-Digital
Characteristics section). For example, if the LM95172EWG is
set for 16-bit resolution before shutdown, then Bit 15 of the
Control/Status register must go high and stay high for the
specified maximum conversion time for 16-bits resolution.
The LM95172EWG will always finish a temperature conver-
sion and update the temperature registers before shutting
down.
Writing a “0” to the Shutdown Bit restores the LM95172EWG
to normal mode.
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LM95172
1.7 INTERNAL REGISTER STRUCTURE
The LM95172EWG has four registers that are accessible by issuing a command byte (a R/W Bit plus the register address: Control/
Status, THIGH, TLOW, and Identification. Which of these registers will be read or written is determined by the Command Byte. See
Section 1.4, "Communicating with the LM95172EWG", for a complete description of the serial communication protocol. The fol-
lowing diagram describes the Command Byte and lists the addresses of the various registers. On power-up, the Command Byte
will point to the Temperature Register by default. The temperature is read by lowering the CS line and then reading the 16-Bit
temperature register; all other registers are accessed by writing a Command Byte after reading the temperature.
All registers can be communicated with, either in Continuous Conversion mode or in Shutdown mode. When the LM95172EWG
has been placed in Shutdown Mode, the Temperature register will contain the temperature data which resulted from the last
temperature conversion (whether it was the result of a continuous-conversion reading or a one-shot reading).
1.7.1 Command Byte
P7 P6 P5 P4 P3 P2 P1 P0
R/W 0 0 0 0 Register Select
Bit <7> Read/Write Bit. Tells the LM95172EWG if the host will be writing to, or reading from, the register to which this byte is
pointing.
Bits <6:3> Not Used. These Bits must be zero. If an illegal address is written, the LM95172EWG will return 0000h on the sub-
sequent read.
Bits <2:0> Pointer Address Bits. Points to desired register. See table below.
P2 P1 P0 Register
0 0 0 Invalid. (Note 6)
0 0 1 Control/Status
0 1 0 THIGH
0 1 1 TLOW
100
Invalid. (Note 6)1 0 1
110
1 1 1 Identification
Power-On Reset state: 00h
Reset Conditions: Upon Power-on Reset
1.7.2 Temperature Register
(Read Only): Default Register
D15 D14 D13 D12 D11 D10 D9 D8
Sign 128°C 64°C 32°C 16°C 8°C 4°C 2°C
D7 D6 D5 D4 D3 D2 D1 D0
1°C 0.5°C 0.25°C 0.125°C 0.0625°C 0.03125°C 0.015625°C Conversion - Toggle/
0.0078125°C
Bit <15:1>: Temperature Data Byte. Reperesents the temperature that was measured by the most recent temperature conversion
in two's complement form. On power-up, this data is invalid until the DAV Bit in the Control/Status Register is high (that is, after
completion of the first conversion).
The resolution is user-programmable from 13-Bit resolution (0.0625°C) through 16-Bit resolution (0.0078125°C). The desired res-
olution is programmed through Bits 4 and 5 of the Control/Status Register. See the description of the Control/Status Register for
details on resolution selection.
The Bits not used for a selected resolution are always set to "0" and are not to be considered part of a valid temperature reading.
For example, for 14-Bit resolution, Bit <1> is not used and, therefore, it is invalid and is always zero.
Bit <0>: Conversion Toggle or, if 16-Bit resolution has been selected, this is the 16-Bit temperature LSB.
When in 13-Bit, 14-Bit, or 15-Bit resolution mode, this Bit toggles each time the Temperature register is read if a conversion has
completed since the last read. If conversion has not completed, the value will be the same as the last read.
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LM95172
When in 16-Bit resolution mode, this is the Least Significant Bit of the temperature data.
Reset Conditions: See Sections 1.1.1 through 1.1.3 for reset conditions.
One-Shot State: 8000h (-256°C)
1.7.3 Control/Status Register
(Read/Write) Pointer Address: 81h (Read); 01h (Write)
D15 D14 D13 D12 D11 D10 D9 D8
SD One-Shot OVERTEMP
Reset
Conversion
Toggle
OVERTEMP
Status THIGH TLOW DAV
D7 D6 D5 D4 D3 D2 D1 D0
OVERTEMP
Disable
OVERTEMP
POL RES1 RES0 0 reserved reserved 0
Bit <15>: Shutdown (SD) Bit. Writing a “1” to this bit and holding it high for at least the specified maximum conversion time, at the
existing temperature resolution setting, enables the Shutdown Mode. Writing a “0” to this bit restores the LM95172EWG to normal
mode.
Bit <14>: One-Shot Bit. When in shutdown mode (Bit <15> is "1"), initates a single temperature conversion and update of the
temperature register with new temperature data. Has no effect when in continuous conversion mode (i.e., when Bit <15> is "0").
Always returns a "0" when read.
Bit <13>: OVERTEMP Reset Bit. Writing a "1" to this Bit resets the OVERTEMP Status bit and, after a possible wait up to one
temperature conversion time, the OVERTEMP pin. It will always return a "0" when read.
Bit <12>: Conversion Toggle Bit. Toggles each time the Control/Status register is read if a conversion has completed since the
last read. If conversion has not been completed, the value will be the same as last read.
Bit <11>: OVERTEMP Status Bit. This Bit is "0" when OVERTEMP output is low and "1" when OVERTEMP output is high. The
OVERTEMP output is reset under the following conditions: (1) Cleared by writing a "1" to the OVERTEMP Reset Bit (Bit <13>) in
this register or (2) Measured temperature falls below the TLOW limit. If the temperature is still above THIGH, and OVERTEMP Reset
is set to "1", then the Bit and the pin clear until the next conversion, at which point the Bit and pin would assert again.
Bit <10>: Temperature High (THIGH) Flag Bit. This Bit is set to "1" when the measured temperature exceeds the THIGH limit stored
in the programmable THIGH register. The flag is reset to "0" when both of two conditions are met: (1) temperature no longer exceeds
the programmed THIGH limit and (2) upon reading the Control/Status Register. If the temperature no longer exceeds the THIGH limit,
the status Bit remains set until it is read by the master so that the system can check the history of what caused the OVERTEMP
to assert.
Bit <9>: Temperature Low (TLOW) Flag Bit. This Bit is set to "1" when the measured temperature falls below the TLOW limit stored
in the programmable TLOW register. The flag is reset to "0" when both of two conditions are met: (1) temperature is no longer below
the programmed TLOW limit and (2) upon reading the Control/Status Register. If the temperature is no longer below, or equal to,
the TLOW limit, the status Bit remains set until it is read by the master so that the system can check the history of what caused the
OVERTEMP to assert.
Bit <8>: Data Available (DAV) Status Bit. This Bit is "0" when the temperature sensor is in the process of converting a new tem-
perature. It is "1" when the conversion is done. It is reset after each read and goes high again after one temperature conversion
is done. In one-shot mode: after initiating a temperature conversion while operating, this status Bit can be monitored to indicate
when the conversion is done. After triggering the one-shot conversion, the data in the temperature register is invalid until this Bit
is high (i.e., after completion of the first conversion).
Bit <7>: OVERTEMP Disable Bit. When set to "0" the OVERTEMP output is enabled. When set to "1" the OVERTEMP output is
disabled. This Bit also controls the OVERTEMP Status Bit (this register, Bit <11>) since that Bit reflects the state of the
OVERTEMP pin.
Bit <6>: OVERTEMP Polarity Bit. When set to "1", OVERTEMP is active-high. When "0" it is active-low.
www.national.com 16
LM95172
Control/Status Register (Continued)
Bit <5:4>: Temperature Resolution Bits. Selects one of four user-programmable temperature data resolutions as indicated in the
following table.
Control/Status
Register
Resolution
Bit 5 Bit 4 Bits °C
0 0 13 0.0625
0 1 14 0.03125
1 0 15 0.015625
1 1 16 0.0078125
Bit <3>: Always write a zero to this Bit.
Bit <2:1>: Reserved Bits. Will return whatever was last written to them. Value is zero on power-up.
Bit <0>: Always write a zero to this Bit.
Reset State: 0000h
Reset Conditions: Upon Power-on Reset.
1.7.4 THIGH: Upper Limit Register
(Read/Write) Pointer Address: 82h (Read); 02h (Write)
D15 D14 D13 D12 D11 D10 D9 D8
Sign 128°C 64°C 32°C 16°C 8°C 4°C 2°C
D7 D6 D5 D4 D3 D2 D1 D0
1°C 0.5°C 0.25°C Reserved
Bit <15:5>: Upper-Limit Temperature byte. If the measured temperature, stored in the temperature register, exceeds this user-
programmable temperature limit, the OVERTEMP pin will assert and the THIGH flag in the Control/Status register will be set to "1".
Bit <4:0>: Reserved. Returns all zeroes when read.
Reset State: 4880h (+145°C)
Reset Conditions: Upon Power-on Reset.
1.7.5 TLOW: Lower Limit Register
(Read/Write) Pointer Address: 83h (Read); 03h (Write)
D15 D14 D13 D12 D11 D10 D9 D8
Sign 128°C 64°C 32°C 16°C 8°C 4°C 2°C
D7 D6 D5 D4 D3 D2 D1 D0
1°C 0.5°C 0.25°C Reserved
Bit <15:5>: Lower-Limit Temperature byte. If the measured temperature that is stored in the temperature register falls below this
user-programmable temperature limit, the OVERTEMP pin will not assert and the TLOW flag in the Control/Status register will be
set to "1".
Bit <4:0>: Reserved. Returns all zeroes when read.
Reset State: 4600h (+140°C)
Reset Conditions: Upon Power-on Reset.
17 www.national.com
LM95172
1.7.6 MFGID: Manufacturer, Product, and Step ID Register
(Read Only) Pointer Address: 87h
D15 D14 D13 D12 D11 D10 D9 D8
10000000
D7 D6 D5 D4 D3 D2 D1 D0
00110000
Bit <15:8>: Manufacturer Identification Byte. Always returns 80h to uniquely identify the manufacturer as National Semiconductor
Corporation.
Bit <7:4>: Product Identification Nibble. Always returns 30h to uniquely identify this part as the LM95172EWG.
Bit <3:0>: Die Revision Nibble. Returns 0h to uniquely identify the revision level as zero.
Reset State: 8030h
Reset Conditions: Upon Power-on Reset.
www.national.com 18
LM95172
2.0 Typical Applications
30076620
FIGURE 13. Temperature monitor using Intel 196 processor
30076619
FIGURE 14. LM95172EWG digital input control using microcontroller's general purpose I/O.
19 www.national.com
LM95172
Physical Dimensions inches (millimeters) unless otherwise noted
10-pin Cerpack Package
LM95172EWG
www.national.com 20
LM95172
Notes
21 www.national.com
LM95172
Notes
LM95172 13-Bit to 16-Bit 200°C Digital Temp Sensor with 3-Wire Interface
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