LM76CNMX-3 National Semiconductor, LM76CNMX-3 Datasheet - Page 8

• Manufacturer Part Number: LM76CNMX-3
• Description: 0.5C/ 1C/ 12-Bit Sign Digital Temperature Sensor and Thermal Window Comparator with Two-Wire Interface
• Manufacturer: National Semiconductor

www.national.com
1.0 Functional Description
Note: Event Interrupt mode is drawn as if the user is reading the part. If the user doesn’t read, the outputs would go low and stay that way until the LM76 is read.
1.4 TEMPERATURE DATA FORMAT
Temperature data can be read from the Temperature and Set
Point registers; and written to the Set Point registers. Tem-
perature data can be read at any time, although reading
faster than the conversion time of the LM76 will prevent data
from being updated. Temperature data is represented by a
13-bit, two’s complement word with an LSB (Least Signifi-
cant Bit) equal to 0.0625˚C:
Temperature
+0.0625˚C
−0.0625˚C
+130˚C
+125˚C
+80˚C
+64˚C
+25˚C
+10˚C
−25˚C
−55˚C
+2˚C
0˚C
0 1000 0 010 0000
0 0111 1101 0000
0 0101 1010 0000
0 0100 0000 0000
0 0001 1001 0000
0 0000 1010 0000
0 0000 0010 0000
0 0000 0000 0001
1 1111 1111 1111
1 1110 0111 0000
1 1100 1001 0000
00 0000 0000
Binary
Digital Output
FIGURE 3. Temperature Response Diagram
(Continued)
07 D0h
00 A0h
1F FFh
1E 70h
1C 90h
08 20h
05 90h
04 00h
01 90h
00 20h
00 01h
00 00h
Hex
8
1.5 SHUTDOWN MODE
Shutdown mode is enabled by setting the shutdown bit in the
Configuration register via the Serial Bus. Shutdown mode re-
duces power supply current to 5 µA typical. T_CRIT_A is re-
set if previously set. Since conversions are stoped during
shutdown, T_CRIT_A and INT will not be operational. The
Serial Bus interface remains active. Activity on the clock and
data lines of the Serial Bus may slightly increase shutdown
mode quiescent current. Registers can be read from and
written to in shutdown mode. The LM76 takes miliseconds to
respond to the shutdown command.
1.6 INT AND T_CRIT_A OUTPUT
The INT and T_CRIT_A outputs are open-drain outputs and
do not have internal pull-ups. A high level will not be ob-
served on these pins until pull-up current is provided from
some external source, typically a pull-up resistor. Choice of
resistor value depends on many system factors but, in gen-
eral, the pull-up resistor should be as large as possible. This
will minimize any errors due to internal heating of the LM76.
The maximum resistance of the pull up, based on LM76
specification for High Level Output Current, to provide a 2
volt high level, is 30K ohms.
1.7 FAULT QUEUE
A fault queue of up to 4 faults is provided to prevent false
tripping when the LM76 is used in noisy environments. The 4
faults must occur consecutively to set flags as well as INT
DS101015-6