Detailed Description
The MAX6633/MAX6634/MAX6635 continuously con-
vert their die temperatures into digital values using their
integrated ADCs. The resulting data is readable at any
time through the SMBus/I
2
C-compatible serial interface.
The device functions as a slave on the SMBus inter-
face, supporting Write Byte, Write Word, Read Byte,
and Read Word commands. Separate addresses can
be configured using the individual address pins.
Figures 5, 6, and 7 show the functional diagrams of the
MAX6633/MAX6634/MAX6635, respectively.
SMBus/I
2
C-Compatible Operation
The MAX6633/MAX6634/MAX6635 are readable and
programmable through their SMBus/I
2
C-compatible
serial interface. Figures 1, 2, and 3 show the timing
details of the clock (SCL) and data (SDA) signals. The
devices function as slaves on the SMBus and support
Write Byte, Write Word, Read Byte, and Read Word
commands. Figure 8 is the MAX6633/MAX6634/
MAX6635 programmer’s model.
Addressing
Separate addresses can be configured using the indi-
vidual address pins. The address of each device is
selected by connecting the address (A_) pins to one of
two potentials: GND or V
CC
. The MAX6635 makes two
address pins available (A0, A1), allowing up to four
devices to be connected to a single bus line. The
MAX6634 makes three address pins available (A0, A1,
A2), allowing up to eight devices to be connected to a
single bus line. The MAX6633 makes four address pins
available (A0, A1, A2, A3), allowing as many as 16
devices to be connected to a single bus line. Table 1
shows the full SMBus/I
2
C address for each device type.
Control Registers (MAX6633)
Three registers control the operation of the MAX6633
(Figure 5 and Tables 2 through 6). The Pointer register
is the first addressed and determines which of the other
two registers is acted upon. The other two are the
Temperature and Configuration registers. The tempera-
ture value is stored as 12 bits plus a sign bit, read only,
and contains the latest temperature data. The true reg-
ister length is 16 bits, with the lower 3 unused in this
part. The digital temperature data contained in the tem-
perature register is in °C, using a two’s-complement
format with 1LSB corresponding to 0.0625°C.
The Configuration register is 8 bits, read/write, and
contains the SMBus timeout disable bit, fault queue
enable bit, and the shutdown bit.
Control Registers (MAX6634)
Six registers control the operation of the MAX6634
(Figure 6 and Tables 2 through 7). The pointer register
is the first addressed and determines which of the other
five registers is acted upon. The other five are the
Temperature, Configuration, High-Temperature
(T
HIGH
), Low-Temperature (T
LOW
), and Hysteresis
(T
HYST
) registers. The temperature value is stored as
12 bits plus a sign bit, read only, and contains the lat-
est temperature data. The true register length is 16 bits,
with the lowest 2 used as status bits, and the third bit
(D2) is unused. The digital temperature data contained
in the temperature register is in °C, using a two’s-com-
plement format with 1LSB corresponding to 0.0625°C.
MAX6633/MAX6634/MAX6635
12-Bit Plus Sign Temperature Sensors with
SMBus/I
2
C-Compatible Serial Interface
_______________________________________________________________________________________ 5
Pin Description
Supply Voltage Input. +3.0V to +5.5V. Bypass V
with a 0.1µF capacitor.
