LM77CIMX-5/NOPB National Semiconductor, LM77CIMX-5/NOPB Datasheet - Page 8

• Manufacturer Part Number: LM77CIMX-5/NOPB
• Description: IC TEMP SENSOR DIGITAL 8-SOIC
• Manufacturer: National Semiconductor

Specifications of LM77CIMX-5/NOPB

• Function: Temp Monitoring System (Sensor)
• Topology: ADC, Comparator, Register Bank
• Sensor Type: Internal
• Sensing Temperature: -55°C ~ 125°C
• Output Type: I²C™
• Output Alarm: Yes
• Output Fan: No
• Voltage - Supply: 3 V ~ 5.5 V
• Operating Temperature: -55°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (3.9mm Width)
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: *LM77CIMX-5; *LM77CIMX-5/NOPB; LM77CIMX-5

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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 LM77 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 LM77 will prevent data from
being updated. Temperature data is represented by a 10-bit,
two's complement word with an LSB (Least Significant Bit)
equal to 0.5°C:
Temperature
+130°C
+125°C
+0.5°C
−0.5°C
+25°C
−25°C
−55°C
0°C
01 0000 0100
00 1111 1010
00 0011 0010
00 0000 0001
00 0000 0000
11 1111 1111
11 1100 1110
11 1001 0010
Binary
Digital Output
FIGURE 3. Temperature Response Diagram
0FAh
3CEh
3FFh
104h
032h
001h
000h
392h
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 reset
if previously set. Since conversions are stoped during shut-
down, 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 LM77 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 LM77.
The maximum allowable resistance of the pull up resistor is
90K Ohms based on the Logic “1” Output Leakage Current
and a 2 volt high output level.
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