LM75AIMX/NOPB National Semiconductor, LM75AIMX/NOPB Datasheet - Page 8

• Manufacturer Part Number: LM75AIMX/NOPB
• Description: IC TEMP SENSOR WATCHDOG 8-SOIC
• Manufacturer: National Semiconductor

Specifications of LM75AIMX/NOPB

• Function: Temp Sensor, Watchdog
• Topology: ADC (Sigma Delta), Comparator, Register Bank
• Sensor Type: Internal
• Sensing Temperature: -55°C ~ 125°C
• Output Type: I²C™
• Output Alarm: Yes
• Output Fan: Yes
• Voltage - Supply: 2.7 V ~ 5.5 V
• Operating Temperature: -55°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (3.9mm Width)
• Temperature Sensor Function: Temp Sensor
• Interface Type: Serial (2-Wire)
• Resolution: 9b
• Package Type: SOIC N
• Operating Temperature (max): 125C
• Operating Temperature Classification: Military
• Operating Supply Voltage (min): 2.7V
• Operating Supply Voltage (typ): 3.3/5V
• Operating Supply Voltage (max): 5.5V
• For Use With: OM6285 - EVAL BOARD I2C-2002-1A568-4002 - DEMO BOARD I2C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: LM75AIMX

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Typical Performance Characteristics
1.0 Functional Description
The LM75A temperature sensor incorporates a band-gap
type temperature sensor and 9-bit ADC (Sigma-Delta Analog-
to-Digital Converter). The temperature data output of the
LM75A is available at all times via the I
is in progress, it will be stopped and restarted after the read.
A digital comparator is also incorporated that compares a se-
ries of readings, the number of which is user-selectable, to
user-programmable setpoint and hysteresis values. The com-
parator trips the O.S. output line, which is programmable for
mode and polarity. The LM75A has an integrated low-pass
filter on both the SDA and the SCL line. These filters increase
communications reliability in noisy environments.
The LM75A also has a bus fault timeout feature. If the SDA
line is held low for longer than t
LM75A will reset to the IDLE state (SDA set to high
impedance) and wait for a new start condition. The TIMEOUT
feature is not functional in Shutdown Mode.
1.1 O.S. OUTPUT, T
In Comparator mode the O.S. Output behaves like a thermo-
stat. The output becomes active when temperature exceeds
the T
ture drops below the T
can be used to turn a cooling fan on, initiate an emergency
system shutdown, or reduce system clock speed. Shutdown
mode does not reset O.S. state in a comparator mode.
In Interrupt mode exceeding T
O.S. will remain active indefinitely until reset by reading any
register via the I
by crossing T
Temperature going below T
indefinitely until being reset by a read. Placing the LM75A in
shutdown mode also resets the O.S. Output.
1.2 POWER UP AND POWER DOWN
The LM75A always powers up in a known state. The power
up default conditions are:
OS
limit, and leaves the active state when the tempera-
OS
, then reset, it can be activated again only by
2
C interface. Once O.S. has been activated
OS
HYST
AND T
limit. In this mode the O.S. output
HYST
OS
TIMEOUT
HYST
. Again, it will remain active
also makes O.S. active but
LIMITS
2
(see specification) the
C bus. If a conversion
Accuracy vs Temperature (LM75A)
8
1.
2.
3.
4.
5.
When the supply voltage is less than about 1.7V, the LM75A
is considered powered down. As the supply voltage rises
above the nominal 1.7V power up threshold, the internal reg-
isters are reset to the power up default values listed above.
1.2.1 Stand-Alone Thermostat Mode
If the LM75A is not connected to the I
will act as a stand-alone thermostat with the power up default
conditions listed above. It is optional, but recommended, to
connect the address pins (A2, A1, A0) and the SCL and SDA
pins together and to a 10k pull-up resistor to +V
noise immunity. Any of these pins may also be tied high sep-
arately through a 10k pull-up resistor.
1.3 I
The LM75A operates as a slave on the I
line is an input (no clock is generated by the LM75A) and the
SDA line is a bi-directional serial data path. According to I
bus specifications, the LM75A has a 7-bit slave address. The
four most significant bits of the slave address are hard wired
inside the LM75A and are “1001”. The three least significant
bits of the address are assigned to pins A2–A0, and are set
by connecting these pins to ground for a low, (0); or to +V
a high, (1).
Therefore, the complete slave address is:
MSB
1
2
Comparator mode
T
T
O.S. active low
Pointer = “00”
C BUS INTERFACE
OS
HYST
= 80°C
= 75°C
0
1265818
0
1
A2
2
C bus on power up, it
2
C bus, so the SCL
A1
S
for better
LSB
A0
S
for
2
C