LM95245EB/NOPB National Semiconductor, LM95245EB/NOPB Datasheet - Page 12

• Manufacturer Part Number: LM95245EB/NOPB
• Description: BOARD EVALUATION FOR LM95245
• Manufacturer: National Semiconductor
• Series: PowerWise®, TruTherm®r

Specifications of LM95245EB/NOPB

• Sensor Type: Temperature
• Sensing Range: -40°C ~ 125°C
• Interface: SMBus (2-Wire/I²C)
• Sensitivity: ±1°C
• Voltage - Supply: 3 V ~ 3.6 V
• Embedded: No
• Utilized Ic / Part: LM95245
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: LM95245EB

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1.6 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 tem-
perature reading errors due to internal heating of the
LM95245. The maximum resistance of the pull-up to provide
a 2.1V high level, based on LM95245 specification for High
Level Output Current with the supply voltage at 3.0V, is
82 kΩ (5%) or 88.7 kΩ (1%).
1.7 T_CRIT OUTPUT AND TCRIT LIMIT
The LM95245's T_CRIT pin is an active-low open-drain out-
put that is triggered when the local and/or the remote tem-
perature conversion is above the limits defined by the Remote
and/or Local Limit registers. The state of the T_CRIT pin will
return to the HIGH state when both the Local and Remote
temperatures are below the values programmed into the Limit
Registers less the value in the Common Hysteresis Register.
Additionally, if the remote temperature exceeds the value in
the Remote TCRIT Limit Register the Status Bit for Remote
TCRIT (RTCRIT), in Status Register 1, is set to 1. In the same
way if the local temperature exceeds the value in the Local
Shared OS and TCRIT Limit Register the Status Bit for the
Shared Local OS and TCRIT (LOC) bit in Status Register 1 is
set to 1.The T_CRIT output and the Status Register flags are
updated after every Local and Remote temperature conver-
sion. See Figure 4
FIGURE 4. T_CRIT Comparator Temperature Response
Temperature
+0.125°C
−0.125°C
+125°C
+25°C
−25°C
−55°C
+1°C
−1°C
0°C
11-bit, 2's complement (10-bit plus sign)
0111 1101 0000 0000
0001 1001 0000 0000
0000 0001 0000 0000
0000 0000 0010 0000
0000 0000 0000 0000
1111 1111 1110 0000
1111 1111 0000 0000
1110 0111 0000 0000
1100 1001 0000 0000
Diagram
Binary
Digital Output
FFE0h
7D00h
FF00h
E700h
C900h
1900h
0100h
0020h
0000h
Hex
30015113
12
1.8 OS OUTPUT AND OS LIMIT
The LM95245's OS/A0 pin is selected as an OS digital output
as described in Section 1.3. As an OS pin, it is activated
whenever the local and/or remote temperature conversion is
above the limits defined by the Limit registers. If the remote
temperature exceeds the value in the Remote OS Limit Reg-
ister the Status Bit for Remote OS (ROS) in Status Register
1 is set to 1. In the same way if the local temperature exceeds
the value in the Local Shared OS and TCRIT Limit Register
the Status Bit for the Shared Local OS and TCRIT (LOC) bit
in Status Register 1 is set to 1. The state of the T_CRIT pin
output will return to the HIGH state when both the Local and
Remote temperatures are below the values programmed into
the Limit Registers less the value in the Common Hysteresis
Register. The OS output and the Status Register flags are
updated after every Local and Remote temperature conver-
sion. See Figure 5.
1.9 DIODE FAULT DETECTION
The LM95245 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, V
D+ is floating, the Remote Temperature reading is –
128.000 °C if signed format is selected and +255.875 °C if
unsigned format is selected. In addition, the Status Register
1 bit D2 is set.
FIGURE 5. OS Temperature Response Diagram
30015115
DD
or