Datasheet

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SBOS363D − JUNE 2006 − REVISED AUGUST 2007
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5
APPLICATIONS INFORMATION
The TMP275 is a digital temperature sensor that is optimal
for thermal management and thermal protection
applications. The TMP275 is Two-Wire and SMBus
interface-compatible, and is specified over a temperature
range of −40°C to +125°C.
The TMP275 requires no external components for
operation except for pull-up resistors on SCL, SDA, and
ALERT, although a 0.1µF bypass capacitor is
recommended, as shown in Figure 1.
TMP275
0.1
µ
F
V+
GND
4
3
7
8
ALERT
(Output)
A
0
6
A
1
5
A
2
2
1
SCL
SDA
To
Two−Wire
Controller
NOTE:SCL,SDA,andALERT
pins require pull−up resistors.
Figure 1. Typical Connections of the TMP275
The sensing device of the TMP275 is the chip itself.
Thermal paths run through the package leads as well as
the plastic package. The lower thermal resistance of metal
causes the leads to provide the primary thermal path.
To maintain accuracy in applications requiring air or
surface temperature measurement, care should be taken
to isolate the package and leads from ambient air
temperature. A thermally-conductive adhesive will assist
in achieving accurate surface temperature measurement.
POINTER REGISTER
Figure 2 shows the internal register structure of the
TMP275. The 8-bit Pointer Register of the devices is used
to address a given data register. The Pointer Register uses
the two LSBs to identify which of the data registers should
respond to a read or write command. Table 1 identifies the
bits of the Pointer Register byte. Table 2 describes the
pointer address of the registers available in the TMP275.
Power-up reset value of P1/P0 is 00.
P7 P6 P5 P4 P3 P2 P1 P0
0 0 0 0 0 0 Register Bits
Table 1. Pointer Register Byte
I/O
Control
Interface
SCL
SDA
Temperature
Register
Configuration
Register
T
LOW
Register
T
HIGH
Register
Pointer
Register
Figure 2. Internal Register Structure of the
TMP275
P1 P0 REGISTER
0 0 Temperature Register (READ Only)
0 1 Configuration Register (READ/WRITE)
1 0 T
LOW
Register (READ/WRITE)
1 1 T
HIGH
Register (READ/WRITE)
Table 2. Pointer Addresses of the TMP275
TEMPERATURE REGISTER
The Temperature Register of the TMP275 is a 12-bit,
read-only register that stores the output of the most recent
conversion. Two bytes must be read to obtain data, and are
described in Table 3 and Table 4. Note that byte 1 is the
most significant byte, followed by byte 2, the least
significant byte. The first 12 bits are used to indicate
temperature, with all remaining bits equal to zero. The
least significant byte does not have to be read if that
information is not needed. Data format for temperature is
summarized in Table 5. Following power-up or reset, the
Temperature Register will read 0°C until the first
conversion is complete.
D7 D6 D5 D4 D3 D2 D1 D0
T11 T10 T9 T8 T7 T6 T5 T4
Table 3. Byte 1 of Temperature Register
D7 D6 D5 D4 D3 D2 D1 D0
T3 T2 T1 T0 0 0 0 0
Table 4. Byte 2 of Temperature Register