Datasheet

The Configuration register is 8 bits, read/write, and con-
tains the SMBus timeout disable bit, fault queue enable
bit, the temperature alarm output polarity select bits, the
interrupt mode select bit, and the shutdown bit. Registers
T
HIGH
and T
LOW
are 16 bits, read/write, and contain the
values that trigger ALERT. Register T
HYST
is 16 bits,
read/write, and contains the values by which the tem-
perature must rise or fall beyond T
HIGH
or T
LOW
, before
ALERT deasserts.
Control Registers (MAX6635)
Seven registers control the operation of the MAX6635
(Figure 7 and Tables 2 through 7). The Pointer regis-
ter is the first addressed and determines which of the
other six registers is acted upon. The other six are the
Temperature, Configuration, High-Temperature (T
HIGH
),
Low-Temperature (T
LOW
), Maximum Temperature
(T
MAX
), and Hysteresis (T
HYST
) registers. The tem-
perature value is stored as 12 bits plus a sign bit, read
only, and contains the latest temperature data. The true
register length is 16 bits, with the lower three used as
status bits. The digital temperature data contained in the
temperature register is in °C, using a two's-complement
format with 1 LSB corresponding to 0.0625°C.
The configuration register is 8 bits, read/write, and
contains the SMBus timeout disable bit, fault queue
enable bit, the temperature alarm output polarity select
bits, the interrupt mode select bit, and the shutdown
Figure 5. MAX6633 Functional Diagram
Figure 4. ADC Conversion Timing Diagram
Figure 3. SMBus Read Timing Diagram
12 BIT + SIGN
ADC
V
CC
CONFIGURATION TEMPERATURE
SMBus INTERFACE
SDA
SCL
A0
A1
A2
A3
0.25s ADC CONVERSION TIME
MAX6633/MAX6634/MAX6635
CONVERSION PERIOD 0.5s
MAX6633/MAX6634/MAX6635
SMBCLK
A = START CONDITION
B = MSB OF ADDRESS CLOCKED INTO SLAVE
C = LSB OF ADDRESS CLOCKED INTO SLAVE
D = R/W BIT CLOCKED INTO SLAVE
A B C D
E
F G H
I
J
SMBDATA
t
SU:STA
t
HD:STA
t
LOW
t
HIGH
t
SU:DAT
K L M
t
SU:STO
t
BUF
E = SLAVE PULLS SMBDATA LINE LOW
F = ACKNOWLEDGE BIT CLOCKED INTO MASTER
G = MSB OF DATA CLOCKED INTO MASTER
H = LSB OF DATA CLOCKED INTO MASTER
I = MASTER PULLS DATA LINE LOW
J = ACKNOWLEDGE CLOCKED INTO SLAVE
K = ACKNOWLEDGE CLEAR PULSE
L = STOP CONDITION, DATA
EXECUTED BY SLAVE
M = NEW START CONDITION
MAX6633/MAX6634/
MAX6635
12-Bit Plus Sign Temperature Sensors
with SMBus/I
2
C-Compatible Serial Interface
www.maximintegrated.com
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