Datasheet

LM95214
SNIS146A MARCH 2007REVISED MARCH 2013
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Local Temperature data is only represented by an 11-bit, two's complement, word with an LSb equal to 0.125°C.
Table 5. 11-bit, 2's complement (10-bit plus sign)
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
+0.125°C 0000 0000 0010 0000 0020h
0°C 0000 0000 0000 0000 0000h
0.125°C 1111 1111 1110 0000 FFE0h
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 LM95214. The maximum resistance of the pull-up to provide a 2.1V high
level, based on LM95214 specification for High Level Output Current with the supply voltage at 3.0V, is 82 kΩ
(5%) or 88.7 kΩ (1%).
TCRIT1, TCRIT2, and TCRIT3 OUTPUTS
The LM95214's TCRIT pins are active-low open-drain outputs and do not include internal pull-up resistors. A
“high” level will not be observed on these pins 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 performance of the device receiving the signal. This will
minimize any internal temperature reading errors due to internal heating of the LM95214. The maximum
resistance of the pull-up to provide a 2.1V high level, based on LM95214 specification for High Level Output
Current with the supply voltage at 3.0V, is 82 kΩ (5%) or 88.7 kΩ (1%). The three TCRIT pins can each sink 6
mA of current and still ensured a "Logic Low" output voltage of 0.4V. If all three pins are set at maximum current
this will cause a power dissipation of 7.2 mW. This power dissipation combined with a thermal resistance of
77.8°C/W will cause the LM95214's junction temperature to rise approximately 0.6°C and thus cause the Local
temperature reading to shift. This can only be cancelled out if the environment that the LM95214 is enclosed in
has stable and controlled air flow over the LM95214, as airflow can cause the thermal resistance to change
dramatically.
Tcrit LIMITS AND TCRIT OUTPUTS
Figure 12 describes a simplified diagram of the temperature comparison and status register logic. Figure 13,
Figure 14, and Figure 15 describe simplified logic diagrams of the circuitry associated with the status registers,
mask registers and the TCRIT output pins.
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