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MAX31875R0TZS+T

P1-P3P4-P6P7-P9P10-P12P13-P15
Detailed Description
The MAX31875 temperature sensor measures
temperature and converts the data into digital form. An
I
2
C-compatible two-wire serial interface allows access to
conversion results. Standard I
2
C commands allow reading
the data and configuring other operating characteristics.
While reading the temperature register, any changes in
measured temperature are ignored until the read is
completed. The temperature register is updated for the
new temperature measurement upon completion of the
read operation.
I
2
C-Compatible Bus Interface
A standard I
2
C-compatible 2-wire serial interface reads
temperature data from the temperature registers and
reads and writes control bits to and from the configuration
registers. In addition, the interface supports useful SMBus
functions, including selectable bus timeout and selectable
Packet Error Checking (PEC).
Normal transactions consist of 2-byte writes and reads. An
additional byte will be appended when PEC is enabled.
Attempting longer transactions is not recommended. A
transaction always begins with a START (S) condition
followed by the slave address and the Write/Read bit.
A 2-byte write transaction begins with the master
generating a START condition and then transmitting the
MAX31875's slave address followed by the Write bit. The
MAX31875 acknowledges with an ACK (A) bit, and the
master transmits the target register, followed by another
ACK from the MAX31875. The master then writes the two
data bytes, and the MAX31875 ACKs each. The master
ends the transaction by generating a STOP (P) condition.
Writing more bytes (not recommended) will simply over-
write the register (e.g., DATA HIGH - DATA LOW - DATA
HIGH - DATA LOW for a 4-byte write).
When Packet Error Checking (PEC) is enabled, the write
transaction is similar except that the PEC byte (calculated
using SLAVE ADDRESS, REGISTER ADDRESS, DATA
HIGH and DATA LOW) is appended by the master
after the ACK bit that follows the second data byte. Any
attempted write that is not a multiple of three bytes will be
ignored. If more than one set of three bytes is written, the
PEC byte is calculated using the bytes listed above, plus
the first PEC byte and the second DATA HIGH and DATA
LOW bytes. Again, writing more than three bytes with
PEC enabled is not recommended.
Figure 1. I
2
C/SMBus Timing Diagram
Figure 2. 2-Byte Write to MAX31875.
Figure 3. 2-Byte Write to MAX31875 with PEC Byte
SCL
SDA
STOP
START
t
BUF
t
HD:STA
t
LOW
t
R
t
HD:DAT
t
F
t
HIGH
t
SU:DAT
t
SU:STA
t
HD:STA
REPEATED
START
t
SP
t
SU:STO
DIRECTION
BITS
CONTENT
M→ S
1
S
M→ S
SLAVE ADDRESS
7
M→ S
1
WR
S→ M
1
A
M→ S
REGISTER SELECT
8
S→ M
1
A
M→ S
DATA HIGH
8
S→ M
1
A
M→ S
DATA LOW
8
S→ M
1
A
M→ S
1
P
DIRECTION
BITS
CONTENT
M→ S
1
S
M→ S
SLAVE ADDRESS
7
M→ S
1
WR
S→ M
1
A
M→ S
REGISTER SELECT
8
S→ M
1
A
M→ S
DATA HIGH
8
S→ M
1
A
M→ S
DATA LOW
8
S→ M
1
A
M→ S
1
P
S→ M
1
A
M→ S
PEC BYTE
8
www.maximintegrated.com
Maxim Integrated
│
7
MAX31875 Low-Power I
2
C Temperature
Sensor in WLP Package
A 2-byte read is slightly more complex than a write.
After transmitting the register byte and receiving an ACK
from the MAX31875, the master generates a REPEAT
START (Sr) and writes the address and a Read bit. The
MAX31875 then ACKs the address/read byte and transmits
the two data bytes. The master ACKs the first and NACKs
the second, signaling that the transaction is complete,
and then generates the STOP condition.
When Packet Error Checking (PEC) is enabled, the read
transaction is similar except that the PEC byte is appended
by the MAX31875 after the ACK bit that follows the second
data byte.
I
2
C Slave Address
The MAX31875 responds to its own I
2
C slave address,
which is factory-programmed to one of the values shown
in Table 1.
Internal Registers
Two two-byte registers contain conversion data, con-
figuration settings, and temperature threshold (T
OS
) and
hysteresis (T
HYST
) values. The pointer register selects
between the registers as shown in the table below. The
pointer register must be written for each I
2
C transaction.
All registers are read and write, except for the read-only
temperature data register. Register addresses are not
auto-incremented during reads and writes.
Write to the configuration register by writing the slave
address byte, the pointer register byte to value 01h, and
the data bytes. The TOS and THYST registers require the
slave address byte, pointer register byte (02h or 03h), and
2 data bytes. If only 1 data byte is written, it is saved in bits
D[15:8] of the respective register. If more than 2 data bytes
are written, the additional data writes to the same register.
Perform a read operation by issuing the slave address
byte (write), pointer byte, repeat START, another slave
address byte (read), and then reading the data byte. If
more than 2 data bytes are read, the additional reads are
from the same register. See Figure 4.
PART NUMBER SLAVE ADDRESS
MAX31875R0 1001000
MAX31875R1 1001001
MAX31875R2 1001010
MAX31875R3 1001011
MAX31875R4 1001100
MAX31875R5 1001101
MAX31875R6 1001110
MAX31875R7 1001111
Table 1. I
2
C Slave Addresses
Figure 4. 2-Byte Read from MAX31875
Figure 5. 2-Byte Read from MAX31875 with PEC Byte
DIRECTION
BITS
CONTENT
M→ S
1
S
M→ S
SLAVE ADDRESS
7
M→ S
1
WR
S→ M
1
A
M→ S
REGISTER SELECT
8
S→ M
1
A
M→ S
1
Sr
M→ S
SLAVE ADDRESS
7
M→ S
1
RD
S→ M
DATA HIGH
8
M→ S
1
A
S→ M
DATA LOW
8
M→ S
1
N
M→ S
1
P
S→ M
1
A
DIRECTION
BITS
CONTENT
M→ S
1
S
M→ S
SLAVE ADDRESS
7
M→ S
1
WR
S→ M
1
A
M→ S
REGISTER SELECT
8
S→ M
1
A
M→ S
1
Sr
M→ S
SLAVE ADDRESS
7
M→ S
1
RD
S→ M
DATA HIGH
8
M→ S
1
A
S→ M
DATA LOW
8
M→ S
1
N
M→ S
1
P
S→ M
1
A
S→ M
PEC BYTE
8
M→ S
1
A
www.maximintegrated.com
Maxim Integrated
│
8
MAX31875 Low-Power I
2
C Temperature
Sensor in WLP Package
Temperature Register
The temperature data format is 16 bits, two’s complement,
and the register is read out in 2 bytes: an upper byte and
a lower byte. Bits D[15:3] contain the temperature data,
but depending on the resolution and data format selected,
some of the lower-value bits may be set to 0. For 8-bit
resolution, the LSB has a value of 1°C, and for 12-bit
resolution, the LSB has a value of 0.0625°C. The MSB
is the sign bit; see Table 3. The MSB is transmitted first.
In addition to the normal temperature data format, an
optional extended data format allows temperatures equal
to or greater than +128°C to be read. In the extended
format, selected by bit 5 of the configuration register, the
MSB is increased from 64°C to 128°C.
Temperature Threshold Registers
The T
OS
and T
HYST
registers use the same data format as
the temperature data register. Note that T
HYST
is intend-
ed to have values less than or equal to T
OS
. Therefore,
a T
HYST
value greater than TOS will be interpreted as
being equal to T
OS
.
Conguration Register
The configuration register contains 16 bits of data and
initiates single conversions (1-shot), enables bus timeout,
controls shutdown, sets the data format, and selects the
automatic conversion rate. The upper byte is compatible
with popular temperature sensors, such as the DS75 and
the lower byte includes additional features. See Table 4.
One-Shot
The One-Shot function helps to reduce average supply
current when continuous conversions are not necessary.
Writing a 1 to D0 while in shutdown mode immediately
begins a new temperature conversion. After the conversion
has completed, the device returns to shutdown mode. D0
returns to 0 when the conversion completes. Writing 1 to
D0 has no effect when not in shutdown.
Timeout
Write 1 to D4 to disable bus timeout.
Write 0 to D4 to enable bus timeout. Bus timeout resets
the I
2
C-compatible interface when SCL is low for more
than 30ms (nominal).
Table 3. Temperature Register Definition
Table 4. Configuration Register Definition
Table 2. Register Functions and POR States
REGISTER
NAME
ADDRESS
(HEX)
NUMBER OF
BYTES
POR STATE
(HEX)
POR STATE
(°C)
READ/WRITE
Temperature 00h 2 0000h 0 RO
Conguration 01h 2 0040h n/a R/W
T
HYST
02h 2 4B00h 75 R/W
T
OS
03h 2 5000h 80 R/W
UPPER BYTE LOWER BYTE COMMENT
D15 D14 D13 D12 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0
Sign 128°C 64°C 32°C 16°C 8°C 4°C 2°C 1°C 0.5°C 0.25°C 0.125°C 0.0625°C 0 0 0
Extended
Format
Sign 64°C 32°C 16°C 8°C 4°C 2°C 1°C 0.5°C 0.25°C 0.125°C 0.0625°C 0 0 0 0
Normal
Format
D15 D14 D13 D12 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0
Over Temp
Status
X X
Fault
Queue
X
Comp/
Int
Shut
Down
Data
Format
Resolution
Time-
out
PEC
Conversion
Rate
One-
Shot
www.maximintegrated.com
Maxim Integrated
│
9
MAX31875 Low-Power I
2
C Temperature
Sensor in WLP Package
P1-P3P4-P6P7-P9P10-P12P13-P15

MAX31875R0TZS+T

Mfr. #:
Buy MAX31875R0TZS+T
Manufacturer:
Maxim Integrated
Description:
SENSOR DIGITAL -10C-100C 4WLP
Lifecycle:
New from this manufacturer.
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