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FIGURE 3. Printed Circuit Board Used for Thermal Resistance Specifications
Typical Performance Characteristics
Static Quiescent Current vs
Temperature
Dynamic Quiescent Current vs
Temperature
Accuracy vs Temperature
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2. The LM75B also has a bus fault timeout feature. If the
SDA line is held low for longer than tTIMEOUT (75 ms
minimum to 325 ms maximum) the LM75B will reset to
the IDLE state (SDA set to high impedance) and wait for
a new start condition.
1.0 Functional Description
The LM75 temperature sensor incorporates a band-gap type
temperature sensor and 9-bit ADC (Delta-Sigma Analog-to-
Digital Converter). The temperature data output of the LM75
is available at all times via the I2C bus. If a conversion 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
comparator trips the O.S. output line, which is programmable
for mode and polarity.
1.1 O.S. OUTPUT, TOS AND THYST LIMITS
In Comparator mode the O.S. Output behaves like a ther-
mostat. The output becomes active when temperature ex-
ceeds the TOS limit, and leaves the active state when the
temperature drops below the THYST limit. In this mode the
O.S. output 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 com-
parator mode.
The LM75B contains all the functionality of the LM75C, plus
two additional features:
1. The LM75B has an integrated low-pass filter on both the
SDA and the SCL line. These filters increase communi-
cations reliability in noisy environments.
In Interrupt mode exceeding TOS also makes O.S. active but
O.S. will remain active indefinitely until reset by reading any
register via the I2C interface. Once O.S. has been activated
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