Datasheet

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SBOS363D − JUNE 2006 − REVISED AUGUST 2007
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6
TEMPERATURE
(°C)
DIGITAL OUTPUT
(BINARY)
HEX
128 0111 1111 1111 7FF
127.9375 0111 1111 1111 7FF
100 0110 0100 0000 640
80 0101 0000 0000 500
75 0100 1011 0000 4B0
50 0011 0010 0000 320
25 0001 1001 0000 190
0.25 0000 0000 0100 004
0 0000 0000 0000 000
−0.25 1111 1111 1100 FFC
−25 1110 0111 0000 E70
−55 1100 1001 0000 C90
Table 5. Temperature Data Format
The user can obtain 9, 10, 11, or 12 bits of resolution by
addressing the Configuration Register and setting the
resolution bits accordingly. For 9-, 10-, or 11-bit resolution,
the most significant bits in the Temperature Register are
used with the unused LSBs set to zero.
CONFIGURATION REGISTER
The Configuration Register is an 8-bit read/write register
used to store bits that control the operational modes of the
temperature sensor. Read/write operations are performed
MSB first. The format of the Configuration Register for the
TMP275 is shown in Table 6, followed by a breakdown of
the register bits. The power-up/reset value of the
Configuration Register is all bits equal to 0.
BYTE D7 D6 D5 D4 D3 D2 D1 D0
1 OS R1 R0 F1 F0 POL TM SD
Table 6. Configuration Register Format
SHUTDOWN MODE (SD)
The Shutdown Mode of the TMP275 allows the user to
save maximum power by shutting down all device circuitry
other than the serial interface, which reduces current
consumption to typically less than 0.1µA. Shutdown Mode
is enabled when the SD bit is 1; the device will shut down
once the current conversion is completed. When SD is
equal to 0, the device will maintain a continuous
conversion state.
THERMOSTAT MODE (TM)
The Thermostat Mode bit of the TMP275 indicates to the
device whether to operate in Comparator Mode (TM = 0)
or Interrupt Mode (TM = 1). For more information on
comparator and interrupt modes, see the High and Low
Limit Registers section.
POLARITY (POL)
The Polarity Bit of the TMP275 allows the user to adjust the
polarity of the ALERT pin output. If POL = 0, the ALERT pin
will be active LOW, as shown in Figure 3. For POL = 1, the
ALERT pin will be active HIGH, and the state of the ALERT
pin is inverted.
Measured
Temperature
T
HIGH
T
LOW
TMP275 ALERT PIN
(Comparator Mode)
POL = 0
TMP275 ALERT PIN
(Interrupt Mode)
POL = 0
TMP275 ALERT PIN
(Comparator Mode)
POL = 1
TMP275 ALERT PIN
(Interrupt Mode)
POL = 1
Read Read
Time
Read
Figure 3. Output Transfer Function Diagrams
FAULT QUEUE (F1/F0)
A fault condition is defined as when the measured
temperature exceeds the user-defined limits set in the
T
HIGH
and T
LOW
Registers. Additionally, the number of
fault conditions required to generate an alert may be
programmed using the fault queue. The fault queue is
provided to prevent a false alert as a result of
environmental noise. The fault queue requires
consecutive fault measurements in order to trigger the
alert function. Table 7 defines the number of measured
faults that may be programmed to trigger an alert condition
in the device. For T
HIGH
and T
LOW
register format and byte
order, see section High and Low Limit Registers.
F1 F0 CONSECUTIVE FAULTS
0 0 1
0 1 2
1 0 4
1 1 6
Table 7. Fault Settings of the TMP275