FM75 Fairchild Semiconductor, FM75 Datasheet - Page 6

• Manufacturer Part Number: FM75
• Description: Low Voltage 2-Wire Digital Temperature Sensor with Thermal Alarm
• Manufacturer: Fairchild Semiconductor

FM75
Comparator Mode
In Comparator Mode, each time a temperature-to-digital
(T-to-D) temperature conversion occurs, the new digital tem-
perature is compared to the value stored in the T
T
temperature measurements are greater than the value stored
in the T
For example, if bits F1 and F0 are equal to “10” (fault
tolerance = 4), four consecutive temperature measurements
must exceed T
output is active, it will remain active until the first time the
measured temperature drops below the temperature stored in
the T
Mode with fault tolerance=2 is illustrated in Figure 1.
6
HYST
HYST
registers. If a fault tolerance number of consecutive
OS
register, the O.S. output will be activated.
register. The operation of the alarm in Comparator
OS
O.S. (Comparator Mode)
to activate the O.S. output. Once the O.S
Temperature-to-Digital
O.S. (Interrupt Mode)
Figure 1. Thermal Alarm Operation in Comparator and Interrupt Modes
Conversion
T
T
HYST
OS
For this example:
Fault Tolerance = 2
Output Polarity = Active Low
OS
and
Interrupt Mode
In Interrupt Mode the O.S. output will first become active
after a fault tolerance number of consecutive temperature
measurements exceed the value stored in the T
(similar to Comparator Mode). Once O.S. is active, it can
only be cleared by a user read from any of the FM75
registers (Temperature, Configuration, T
putting the FM75 into Shutdown Mode (i.e., by setting the
shutdown bit in the Configuration Register to “1”). Once
cleared, the O.S. output can only be activated the next time
by a fault tolerance number of consecutive temperature
measurements that are lower than the value stored in T
Again, once it is activated the O.S. output can only be
deactivated by a user read or shutdown. Thus, in Interrupt
Mode the activate/clear cycle for O.S. has the following
pattern: temperature > T
clear, temperature > T
alarm in Interrupt Mode with fault tolerance=2 is also
illustrated in Figure 1.
Read (or Shutdown)
OS
OS
, clear, etc. The operation of the
, clear, temperature < T
PRODUCT SPECIFICATION
OS
REV. 1.0.4 10/3/02
, or T
OS
HYST
register
HYST
) or by
HYST
,
.