Datasheet

LM95241
SNIS143E –AUGUST 2006–REVISED MARCH 2013 www.ti.com
Table 5. 13-bit, unsigned binary
Temperature Digital Output
Binary Hex
+255.875°C 1111 1111 1110 0000 FFE0h
+255°C 1111 1111 0000 0000 FF00h
+201°C 1100 1001 0000 0000 C900h
+125°C 0111 1101 0000 0000 7D00h
+25°C 0001 1001 0000 0000 1900h
+1°C 0000 0001 0000 0000 0100h
+0.03125°C 0000 0000 0000 1000 0008h
0°C 0000 0000 0000 0000 0000h
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 available in two 8-bit registers. Unused bits will
always report "0". Local temperature readings greater than +127.75°C are clamped to +127.75°C, they will not
roll-over to negative temperature readings.
Temperature Digital Output
Binary Hex
+125°C 0111 1101 0000 0000 7D00h
+25°C 0001 1001 0000 0000 1900h
+1°C 0000 0001 0000 0000 0100h
+0.25°C 0000 0000 0100 0000 0040h
0°C 0000 0000 0000 0000 0000h
−0.25°C 1111 1111 1100 0000 FFC0h
−1°C 1111 1111 0000 0000 FF00h
−25°C 1110 0111 0000 0000 E700h
−55°C 1100 1001 0000 0000 C900h
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 LM95241. The maximum resistance of the pull-up to provide a 2.1V high
level, based on LM95241 specification for High Level Output Current with the supply voltage at 3.0V, is
82kΩ(5%) or 88.7kΩ(1%).
DIODE FAULT DETECTION
The LM95241 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
DD
or D+ is floating, the Remote
Temperature reading is –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.
COMMUNICATING WITH THE LM95241
The data registers in the LM95241 are selected by the Command Register. At power-up the Command Register
is set to “00”, the location for the Read Local Temperature Register. The Command Register latches the last
location it was set to. Each data register in the LM95241 falls into one of four types of user accessibility:
1. Read only
2. Write only
3. Write/Read same address
4. Write/Read different address
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