lm73cimkx-1 National Semiconductor Corporation, lm73cimkx-1 Datasheet - Page 8

• Manufacturer Part Number: lm73cimkx-1
• Description: 2.7v, Sot-23, 11-to-14 Bit Digital Temperature Sensor With 2-wire Interface
• Manufacturer: National Semiconductor Corporation

www.national.com
1.0 Functional Description
The LM73 is a digital temperature sensor that senses the
temperature of its die using a sigma-delta analog-to-digital
converter and stores the temperature in the Temperature
Register. The LM73’s 2-wire serial interface is compatible
with SMBus 2.0 and I
fication for a detailed description of the differences between
the I
The temperature resolution is programmable, allowing the
host system to select the optimal configuration between
sensitivity and conversion time. The LM73 can be placed in
shutdown to minimize power consumption when tempera-
ture data is not required. While in shutdown, a 1-shot con-
version mode allows system control of the conversion rate
for ultimate flexibility.
The LM73 features the following registers. See Section 2.0
for a complete list of the pointer address, content, and reset
state of each register.
1. Pointer Register
2. Temperature Register
3. Configuration Register
4. T
5. T
6. Control/Status Register
7. Identification Register
1.1 POWER-ON RESET
The power-on reset (POR) state is the point at which the
supply voltage rises above the power-on reset threshold
(specified in the electrical specifications table), generating
an internal reset. Each of the registers contains a defined
value upon POR and this data remains there until any of the
following occurs:
1. The first temperature conversion is completed, causing
2. The master writes different data to any R/W bits
3. The LM73 is powered down
1.2 ONE-SHOT CONVERSION
The LM73 features a one-shot conversion bit, which is used
to initiate a single conversion and comparison cycle when
the LM73 is in shutdown mode. While the LM73 is in shut-
down mode, writing a "1" to the One-Shot bit in the Configu-
ration Register will cause the LM73 to perform a single
temperature conversion and update the Temperature Regis-
ter and the affected status bits. Operating the LM73 in this
one-shot mode allows for extremely low average-power con-
sumption, making it ideal for low-power applications.
When the One-Shot bit is set, the LM73 initiates a tempera-
ture conversion. After this initiation, but before the comple-
tion of the conversion and resultant register updates, the
LM73 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
the Temperature Register and various status bits to be
updated internally, depending on the value of the mea-
sured temperature
2
C bus and SMBus.
HIGH
LOW
Register
Register
2
C. Please see the SMBus 2.0 speci-
8
present before initiating the one-shot conversion. After the
temperature measurement is complete, the DAV flag will be
set to "1" and the temperature register will contain the result-
ant measured temperature.
1.3 TEMPERATURE DATA FORMAT
The resolution of the temperature data and the size of the
data word are user-selectable through bits RES1 and RES0
in the Control/Status Register. By default, the LM73 tem-
perature stores the measured temperature in an 11-bit (10
bits plus sign) word with one least significant bit (LSB) equal
to 0.25˚C. The maximum word size is 14 bits (13-bits plus
sign) with a resolution of 0.03125 ˚C/LSB.
The temperature data is reported in 2’s complement format.
The word is stored in the 16-bit Temperature Register and is
left justified in this register. Unused temperature-data bits
are always reported as "0".
Temperature
Temperature
RES1
CONTROL BIT
+0.125˚C
−0.125˚C
0
0
1
1
+0.25˚C
−0.25˚C
+150˚C
+150˚C
+25˚C
−25˚C
−40˚C
+25˚C
−25˚C
−40˚C
+1˚C
−1˚C
+1˚C
−1˚C
0˚C
0˚C
RES0
0
1
0
1
11-bit (10-bit plus sign)
12-bit (11-bit plus sign)
0100 1011 0000 0000
0000 1100 1000 0000
0000 0000 1000 0000
0000 0000 0010 0000
0000 0000 0000 0000
0100 1011 0000 0000
0000 1100 1000 0000
0000 0000 1000 0000
0000 0000 0001 0000
0000 0000 0000 0000
1110 1100 0000 0000
1110 1100 0000 0000
1111 0011 1000 0000
1111 0011 1000 0000
1111 1111 1000 0000
1111 1111 1000 0000
1111 1111 1110 0000
1111 1111 1111 0000
WORD SIZE
12 bits
13 bits
14 bits
11 bits
Binary
Binary
Digital Output
Digital Output
DATA FORMAT
0.03125 ˚C/LSB
0.0625 ˚C/LSB
RESOLUTION
0.125 ˚C/LSB
0.25 ˚C/LSB
FFE0h
EC00h
EC00h
4B00h
0C80h
FF80h
F380h
4B00h
0C80h
FFF0h
FF80h
F380h
0080h
0020h
0000h
0080h
0010h
0000h
Hex
Hex