LM95231_06 NSC [National Semiconductor], LM95231_06 Datasheet - Page 10

• Manufacturer Part Number: LM95231_06
• Description: Precision Dual Remote Diode Temperature Sensor with SMBus Interface and TruTherm Technology
• Manufacturer: NSC [National Semiconductor]

www.national.com
1.0 Functional Description
1.4 TEMPERATURE DATA FORMAT
Temperature data can only be read from the Local and
Remote Temperature registers .
Remote temperature data with the digital filter off is repre-
sented by an 11-bit, two’s complement word or unsigned
binary word with an LSb (Least Significant Bit) equal to
0.125˚C. The data format is a left justified 16-bit word avail-
able in two 8-bit registers. Unused bits will always report "0".
Remote temperature data with the digital filter on is repre-
sented by a 13-bit, two’s complement word or unsigned
binary word with an LSb (Least Significant Bit) equal to
0.03125˚C (1/32˚C). The data format is a left justified 16-bit
word available in two 8-bit registers. Unused bits will always
report "0".
Temperature
Temperature
Temperature
+255.875˚C
+0.03125˚C
−0.03125˚C
+0.125˚C
−0.125˚C
+0.125˚C
+125˚C
+255˚C
+201˚C
+125˚C
+125˚C
+25˚C
−25˚C
−55˚C
+25˚C
+25˚C
−25˚C
−55˚C
+1˚C
−1˚C
+1˚C
+1˚C
−1˚C
0˚C
0˚C
0˚C
11-bit, 2’s complement (10-bit plus sign)
13-bit, 2’s complement (12-bit plus sign)
11-bit, unsigned binary
0001 1001 0000 0000
0000 0001 0000 0000
0000 0000 0010 0000
0000 0000 0000 0000
0001 1001 0000 0000
0000 0001 0000 0000
0000 0000 0010 0000
0000 0000 0000 0000
0001 1001 0000 0000
0000 0001 0000 0000
0000 0000 0000 1000
0000 0000 0000 0000
1100 1001 0000 0000
1100 1001 0000 0000
1100 1001 0000 0000
0111 1101 0000 0000
1110 0111 0000 0000
0111 1101 0000 0000
0111 1101 0000 0000
1110 0111 0000 0000
1111 1111 0000 0000
1111 1111 0000 0000
1111 1111 0000 0000
1111 1111 1110 0000
1111 1111 1110 0000
1111 1111 1111 1000
Binary
Binary
Binary
Digital Output
Digital Output
Digital Output
(Continued)
7D00h
FFE0h
C900h
FFE0h
C900h
7D00h
7D00h
FFF8h
C900h
1900h
0100h
0020h
0000h
FF00h
E700h
FF00h
1900h
0100h
0020h
0000h
1900h
0100h
0008h
0000h
FF00h
E700h
Hex
Hex
Hex
10
Local Temperature data is represented by a 10-bit, two’s
complement word with an LSb (Least Significant Bit) equal to
0.25˚C. The data format is a left justified 16-bit word avail-
able in two 8-bit registers. Unused bits will always report "0".
Local temperature readings greater than +127.875˚C are
clamped to +127.875˚C, they will not roll-over to negative
temperature readings.
1.5 SMBDAT OPEN-DRAIN OUTPUT
The SMBDAT output is an open-drain output and does not
have internal pull-ups. A “high” level will not be observed on
this pin until pull-up current is provided by some external
source, typically a pull-up resistor. Choice of resistor value
depends on many system factors but, in general, the pull-up
resistor should be as large as possible without effecting the
SMBus desired data rate. This will minimize any internal
temperature reading errors due to internal heating of the
LM95231. The maximum resistance of the pull-up to provide
a 2.1V high level, based on LM95231 specification for High
Level Output Current with the supply voltage at 3.0V, is 82kΩ
(5%) or 88.7kΩ (1%).
1.6 DIODE FAULT DETECTION
The LM95231 is equipped with operational circuitry designed
to detect fault conditions concerning the remote diodes. In
the event that the D+ pin is detected as shorted to GND, D−,
V
–128.000 ˚C if signed format is selected and +255.875 if
unsigned format is selected. In addition, the appropriate
status register bits RD1M or RD2M (D1 or D0) are set. When
TruTherm mode is active the condition of diode short of D+
to D− will not be detected. Connecting a 2N3904 transistor
with TruTherm mode active may cause a detection of a diode
fault.
DD
Temperature
Temperature
+255.875˚C
+0.03125˚C
or D+ is floating, the Remote Temperature reading is
+0.25˚C
−0.25˚C
+255˚C
+201˚C
+125˚C
+125˚C
+25˚C
+25˚C
−25˚C
−55˚C
+1˚C
+1˚C
−1˚C
0˚C
0˚C
13-bit, unsigned binary
1100 1001 0000 0000
0001 1001 0000 0000
0000 0001 0000 0000
0000 0000 0000 1000
0000 0000 0000 0000
0001 1001 0000 0000
0000 0001 0000 0000
0000 0000 0100 0000
0000 0000 0000 0000
1100 1001 0000 0000
0111 1101 0000 0000
0111 1101 0000 0000
1110 0111 0000 0000
1111 1111 0000 0000
1111 1111 1100 0000
1111 1111 0000 0000
1111 1111 1110 0000
Binary
Binary
Digital Output
Digital Output
FFE0h
FFC0h
FF00h
C900h
7D00h
7D00h
FF00h
E700h
C900h
1900h
0100h
0008h
0000h
1900h
0100h
0040h
0000h
Hex
Hex