General Description
The MAX6633/MAX6634/MAX6635 combine a tempera-
ture sensor, a programmable overtemperature alarm,
and an SMBus™/I2C™-compatible serial interface into
a single package. They convert their die temperatures
into digital values using internal analog-to-digital con-
verters (ADCs). The result of the conversion is then held
in a temperature register as a 12-bit + sign value, allow-
ing 0.0625°C resolution, readable at any time through
the serial interface. The devices are capable of reading
temperatures up to +150°C.
The MAX6633/MAX6634/MAX6635 feature a shutdown
mode that saves power by turning off everything except
the power-on reset (POR) and the serial interface. The
devices can be configured to separate addresses,
allowing multiple devices to be used on the same bus.
The MAX6633 has four address pins, allowing up to 16
devices to be connected to a single bus. The MAX6634
has three address pins, allowing up to eight devices to
be connected to a single bus. The MAX6635 has two
address pins, allowing up to four devices to be con-
nected to a single bus.
The MAX6633/MAX6634/MAX6635 make temperature
data available for transfer over the serial interface. The
MAX6634 incorporates a dual-mode ALERT output
(open drain) and can serve as an upgraded alternative
to the LM75. The MAX6635 includes an ALERT output
and an OVERT output (both open drain) and can func-
tion as an upgraded replacement for the LM76 in most
applications. The MAX6634/MAX6635 feature user-pro-
grammable temperature thresholds. All three devices
come in an 8-pin SO package.
Applications
Battery Temperature Alarms
PC Temperature Control
Automotive Equipment
Features
♦+3V to +5.5V Supply Range
♦Accuracy
±1°C max (0°C to +50°C)
±1.5°C max (-20°C to +85°C)
±2.5°C max (-40°C to +125°C)
±2.5°C typ (+150°C)
♦User-Programmable Temperature Thresholds
(MAX6634/MAX6635)
♦User-Configurable Alarm Output(s)
(MAX6634/MAX6635)
♦Ability to Respond to SMBus/I2C-Compatible Alert
Response Address (MAX6634/MAX6635)
♦OVERT Output for System Shutdown (MAX6635)
♦Multiple Devices per Bus
16 devices (MAX6633)
8 devices (MAX6634)
4 devices (MAX6635)
MAX6633/MAX6634/MAX6635
12-Bit Plus Sign Temperature Sensors with
SMBus/I2C-Compatible Serial Interface
________________________________________________________________
Maxim Integrated Products
1
Ordering Information
19-2120; Rev 0; 8/01
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
EVALUATION KIT
AVAILABLE
PART TEMP. RANGE PIN-PACKAGE
MAX6633MSA -55°C to +150°C 8 SO
MAX6634MSA -55°C to +150°C 8 SO
MAX6635MSA -55°C to +150°C 8 SO
SMBus is a trademark of Intel Corp.
I2C is a trademark of Philips Corp.
VCC
VCC
SCL
SDA 1
5
8
2
3TO SYSTEM
SHUTDOWN
A0 A1 GND
+3.0V TO +5.5V
0.1μF
ALERT
OVERT
MAX6635
467
10kΩ1kΩ1kΩ10kΩ
TO INTERRUPT
CONTROLLER
TO SMBus/I2C
MASTER
Typical Operating Circuit
Pin Configurations appear at end of data sheet.
MAX6633/MAX6634/MAX6635
12-Bit Plus Sign Temperature Sensors with
SMBus/I2C-Compatible Serial Interface
2 _______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
(VCC = +3.0V to +5.5V, TA= -55°C to +125°C, unless otherwise noted. Typical values are VCC = +3.3V, TA= +25°C, unless other-
wise noted.)
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
VCC, SDA, SCL......................................................-0.3V to +6.0V
All Other Pins ................................................-0.3V to VCC +0.3V
SDA, ALERT, OVERT Current .............................-1mA to +50mA
ESD Protection (Human Body Model)................................2000V
Continuous Power Dissipation (TA= +70°C)
8-Pin SO (derate 5.88mW/°C above +70°C)................471mW
Junction Temperature......................................................+150°C
Operating Temperature Range .........................-55°C to +150°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10s) ................................+300°C
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
TEMPERATURE-TO-DIGITAL CONVERTER CHARACTERISTICS
Supply Range VCC 3.0 5.5 V
0°C ≤ TA = ≤ +50°C, VCC = +3.3V -1.0 ±0.4 +1.0
-20°C ≤ TA = ≤ +85°C, VCC = +3.3V -1.5 ±0.6 +1.5
-40°C ≤ TA = ≤ 125°C, VCC = +3.3V -2.5 ±1.0 +2.5
TA = -55°C, VCC = +3.3V ±1.5 +2.8
Accuracy (Note 1)
TA = +150°C, VCC = +3.3V ±2.5
°C
Power-Supply Rejection Ratio PSRR 0.2 0.5 °C/V
POR Threshold Hysteresis 90 mV
VCC = +3.0V, SMBus inactive 12 20
Supply Current in Shutdown VCC = +5.5V, SMBus inactive 20 30 µA
VCC = +3.0V, SMBus inactive 150
Average Operating Current VCC = +5.5V, SMBus inactive 200 µA
VCC = +3.0V, SMBus inactive 270 350
Peak Operating Current (Note 2) VCC = +5.5V, SMBus inactive 350 700 µA
Conversion Rate 1.4 2 2.4 Hz
DIGITAL INTERFACE
Logic Input Low Voltage VIL VCC = +3.0V to +5.5V 0.65 V
VCC = +3V 2.2 V
Logic Input High
Voltage VIH VCC = +5.5V 2.4
Input Leakage Current II_LEAK VIN = GND or VCC ±1µA
Output Low Sink Current IOL VOL = 0.6V (SMBDATA,
ALERT, OVERT)6mA
Output Leakage Current IO_LEAK ALERT, OVERT at VCC ±1µA
Input Capacitance CIN 5pF
MAX6633/MAX6634/MAX6635
12-Bit Plus Sign Temperature Sensors with
SMBus/I2C-Compatible Serial Interface
_______________________________________________________________________________________ 3
ELECTRICAL CHARACTERISTICS (continued)
(VCC = +3.0V to +5.5V, TA= -55°C to +125°C, unless otherwise noted. Typical values are VCC = +3.3V, TA= +25°C, unless other-
wise noted.)
Note 1: Guaranteed by design and characterization.
Note 2: Peak operating current measured during conversion. See Figure 4.
Note 3: Guaranteed by design, not production tested.
Note 4: A master device must provide a hold time of at least 300ns for the SDA signal in order to bridge the undefined region of
SCL’s falling edge.
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
SMBus TIMING (Note 3, Figures 1, 2, and 3)
Serial Clock Frequency fSCL 10 100 kHz
Bus Free Time Between STOP
and START Condition tBUF 4.7 µs
START Condition Setup Time 4.7 µs
Repeat START Condition Setup
Time tSU:STA 90% to 90% 4.7 µs
START Condition Hold Time tHD:STA 10% of SMBDATA to 90% of SMBCLK 4 µs
STOP Condition Setup Time tSU:STO 90% of SMBCLK to 10% of SMBDATA 4 µs
Data Setup Time tSU: DAT 90% of SMBDATA to 10% of SMBCLK 250 ns
Data Hold Time (Note 4) tHD: DAT 300 ns
Receive SCL/SDA Rise Time tR1µs
SCL/SDA Fall Time (Note 4) tF300 ns
Clock Low Period tLOW 10% to 10% 4.7 µs
Clock High Period tHIGH 90% to 90% 4 µs
SMBus Timeout 25 48 ms
MAX6633/MAX6634/MAX6635
12-Bit Plus Sign Temperature Sensors with
SMBus/I2C-Compatible Serial Interface
4 _______________________________________________________________________________________
Typical Operating Characteristics
(VCC = +3.3V, TA= +25°C, unless otherwise noted.)
50
40
30
20
0
-55 550 110 165
SHUTDOWN SUPPLY CURRENT
vs. TEMPERATURE
MAX6633/4/5 toc01
TEMPERATURE (°C)
SHUTDOWN SUPPLY CURRENT (μA)
10
VCC = +5.5V
VCC = +3.3V
400
300
200
100
0
-55 550 110 165
AVERAGE SUPPLY CURRENT
vs. TEMPERATURE
MAX6633/4/5 toc02
TEMPERATURE (°C)
AVERAGE SUPPLY CURRENT (μA)
VCC = +5.5V
VCC = +3.3V
5
-1
10 10k 10M
TEMPERATURE ERROR
vs. SUPPLY NOISE FREQUENCY
0
MAX6633/4/5 toc03
SUPPLY NOISE FREQUENCY (Hz)
TEMPERATURE ERROR (°C)
3
2
1
4
VIN = SQUARE WAVE APPLIED TO
VCC WITH NO BYPASS
CAPACITOR
VIN = 200mVp-p
VIN = 200mVp-p
0
30
20
10
40
50
60
70
80
90
100
0 5 10 15 20
RESPONSE TO THERMAL SHOCK
MAX6633/4/5 toc04
TIME (s)
TEMPERATURE (°C)
VCC = +5.5V
DEVICE IMMERSED IN +85°C
FLUORINERT BATH
3
2
0
-2
-3
-40 400 80 120 160
TEMPERATURE ERROR
vs. TEMPERATURE
MAX6633/4/5 toc05
TEMPERATURE (°C)
TEMPERATURE ERROR (°C)
VCC = +3.3V
VCC = +5.5V
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/I2C-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/I2C-Compatible Operation
The MAX6633/MAX6634/MAX6635 are readable and
programmable through their SMBus/I2C-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 VCC. 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/I2C 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
(THIGH), Low-Temperature (TLOW), and Hysteresis
(THYST) 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/I2C-Compatible Serial Interface
_______________________________________________________________________________________ 5
Pin Description
PIN
MAX6633 MAX6634 MAX6635 NAME FUNCTION
1 1 1 SDA Serial Data Input/Output. Open drain.
2 2 2 SCL Serial Clock Input
3 — — A3 Address Pin
4 4 4 GND Ground
5 5 — A2 Address Pin
6 6 6 A1 Address Pin
7 7 7 A0 Address Pin
888 V
CC Supply Voltage Input. +3.0V to +5.5V. Bypass VCC to GND
with a 0.1µF capacitor.
—3 5 ALERT ALERT Output. Open drain.
—— 3 OVERT OVERT Output. Open drain.
MAX6633/MAX6634/MAX6635
12-Bit Plus Sign Temperature Sensors with
SMBus/I2C-Compatible Serial Interface
6 _______________________________________________________________________________________
Write Byte Format
S ADDRESS WR ACK COMMAND ACK DATA ACK P
7 bits 8 bits 8 bits
Slave Address:
equivalent
to chip-select line of a 3-
wire interface
Command Byte: selects
register you are writing to
Data Byte: data goes into the register set by the
command byte
Write Word Format
S ADDRESS WR ACK COMMAND ACK DATA ACK DATA ACK P
7 bits 8 bits 8 bits
(MSB)
8 bits
(LSB)
Slave Address:
equivalent to chip-select
line of a
3-wire interface
Command Byte:
selects register you
are writing to
Data Bytes: data goes into the
register set by the command
byte
Read Byte Format
S ADDRESS WR ACK COMMAND ACK S ADDRESS RD ACK DATA /// P
7 bits 8 bits 7 bits 8 bits
Slave Address: equivalent
to chip-select line
Command Byte:
selects register you
are reading from
Slave Address: repeated due to
change in data-flow direction
Data Byte: reads from the
register set by the command
byte
Read Word Format
S ADDRESS WR ACK COMMAND ACK S ADDRESS RD ACK DATA ACK DATA /// P
7 bits 8 bits 7 bits 8 bits
(MSB)
8 bits
(LSB)
Slave Address:
equivalent to chip-
select line
Command Byte:
selects register you
are reading from
Slave Address: repeated
due to change in data-flow
direction
Data Bytes: reads from the
register set by the command
byte
S = Start condition Shaded = Slave transmission
P = Stop condition /// = Not acknowledged
Figure 1. SMBus Protocols
Figure 2. SMBus Write Timing Diagram
SMBCLK
AB CD
EFG H
IJK
SMBDATA
tSU:STA tHD:STA
tLOW tHIGH
tSU:DAT tHD:DAT tSU:STO tBUF
A = START CONDITION
B = MSB OF ADDRESS CLOCKED INTO SLAVE
C = LSB OF ADDRESS CLOCKED INTO SLAVE
D = R/W BIT CLOCKED INTO SLAVE
E = SLAVE PULLS SMBDATA LINE LOW
LM
F = ACKNOWLEDGE BIT CLOCKED INTO MASTER
G = MSB OF DATA CLOCKED INTO SLAVE
H = LSB OF DATA CLOCKED INTO SLAVE
I = SLAVE PULLS SMBDATA LINE LOW
J = ACKNOWLEDGE CLOCKED INTO MASTER
K = ACKNOWLEDGE CLOCK PULSE
L = STOP CONDITION, DATA EXECUTED BY SLAVE
M = NEW START CONDITION
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
bit. Registers THIGH and TLOW are 16 bits, read/write,
and contain the values that trigger ALERT. Register
THYST is 16 bits, read/write, and contains the values by
which the temperature must rise or fall beyond THIGH or
TLOW, before ALERT deasserts.
Control Registers (MAX6635)
Seven registers control the operation of the MAX6635
(Figure 7 and Tables 2 through 7). The Pointer register
is the first addressed and determines which of the other
six registers is acted upon. The other six are the
Temperature, Configuration, High-Temperature
(THIGH), Low-Temperature (TLOW), Maximum
Temperature (TMAX), and Hysteresis (THYST) registers.
The temperature 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 con-
tained in the temperature 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, the temperature alarm output polarity select
bits, the interrupt mode select bit, and the shutdown
MAX6633/MAX6634/MAX6635
12-Bit Plus Sign Temperature Sensors with
SMBus/I2C-Compatible Serial Interface
_______________________________________________________________________________________ 7
Figure 3. SMBus Read Timing Diagram
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
AB CD
EFG H
IJ
SMBDATA
tSU:STA tHD:STA
tLOW tHIGH
tSU:DAT
KLM
tSU:STO tBUF
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
0.25s ADC CONVERSION TIME
MAX6633/MAX6634/MAX6635
CONVERSION PERIOD 0.5s
MAX6633/MAX6634/MAX6635
Figure 4. ADC Conversion Timing Diagram
12 BIT + SIGN
ADC
VCC
CONFIGURATION TEMPERATURE
SMBus INTERFACE
SDA
SCL
A0
A1
A2
A3
Figure 5. MAX6633 Functional Diagram
MAX6633/MAX6634/MAX6635
12-Bit Plus Sign Temperature Sensors with
SMBus/I2C-Compatible Serial Interface
8 _______________________________________________________________________________________
CMP
VCC
ALERT
CONFIGURATION TEMPERATURE TLOW THIGH
SMBus INTERFACE
SDA
SCL
A0
A1
A2
CMP
12 BIT + SIGN
ADC
Figure 6. MAX6634 Functional Diagram
CMP
VCC
ALERT
OVERT
CONFIGURATION TEMPERATURE TMAX THIGH
TLOW
SMBus INTERFACE
SDA
SCL
A0
A1
CMP
CMP
12 BIT + SIGN
ADC
Figure 7. MAX6635 Functional Diagram
MAX6633/MAX6634/MAX6635
12-Bit Plus Sign Temperature Sensors with
SMBus/I2C-Compatible Serial Interface
_______________________________________________________________________________________ 9
INTERFACE
TEMPERATURE
(READ ONLY)
POINTER = 00h
CONFIGURATION
(READ/WRITE, SETS OPERATING
MODES)
POINTER = 01h
POINTER REGISTER
(SELECTS REGISTER FOR
COMMUNICATION)
DATA ADDRESS
SDA
SCL
THYST SET POINT
(READ/WRITE)
POINTER = 02h
(MAX6634/MAX6635 ONLY)
TLOW SET POINT
(READ/WRITE)
POINTER = 04h
(MAX6634/MAX6635 ONLY)
TMAX SET POINT
(READ/WRITE)
POINTER = 03h
(MAX6635 ONLY)
THIGH SET POINT
(READ/WRITE)
POINTER = 05h
(MAX6634/MAX6635 ONLY)
Figure 8. MAX6633/MAX6634/MAX6635 Programmer’s Model
MAX6633/MAX6634/MAX6635
bit. Registers THIGH and TLOW are 16 bits, read/write,
and contain values that trigger ALERT and OVERT.
Register THYST is 16 bits, read/write, and contains the
values by which the temperature must rise or fall
beyond THIGH, TLOW, or TMAX, before ALERT or
OVERT deassert.
Temperature Conversion
An on-chip bandgap reference produces a signal pro-
portional to absolute temperature (PTAT), as well as the
temperature-stable reference voltage necessary for the
analog-to-digital conversion. The PTAT signal is digi-
tized by the on-board ADC to a resolution of 0.0625°C.
The resulting digital value is placed in the Temperature
register. The temperature conversion runs continuously
and asynchronously from the serial interface at a rate of
500ms per conversion. When the Temperature register
is read, the conversion in progress is aborted. The bus
transaction is completed by a stop condition.
Fault Queue (MAX6634/MAX6635)
A programmable fault queue on the MAX6634/
MAX6635 eliminates spurious alarm activity in noisy
environments. The queue sets the number of consecu-
tive out-of-tolerance temperature readings that must
occur before the ALERT or OVERT alarm outputs are
toggled. An out-of-tolerance reading is above THIGH or
TMAX or below TLOW. The fault queue depth defaults to
1 at power-up and may be programmed—through the
Configuration register—to four consecutive conver-
sions. Any time the conversion result is in tolerance,
and the particular alarm output is not asserted, the
queue is cleared, even if it contains some out-of-toler-
ance counts. Additionally, the fault queue automatically
clears at power-up and in shutdown. Whenever the
fault queue is cleared, the alarm outputs are deassert-
ed. Figure 9 is the alarm output and reset diagram.
12-Bit Plus Sign Temperature Sensors with
SMBus/I2C-Compatible Serial Interface
10 ______________________________________________________________________________________
** ***
*IN INTERRUPT MODE, READING THE DEVICE CLEARS ALERT.
OTHERWISE, IT WOULD REMAIN LOW INDEFINITELY UNTIL CLEARED.
TMAX
TMAX - THYST
THIGH
THIGH - THYST
TLOW
TLOW + THYST
ALERT
COMPARATOR MODE
ALERT
INTERRUPT MODE
OVERT
COMPARATOR MODE
ONLY
Figure 9. Alarm Output and Reset Diagram
Temperature Alert
(MAX6634/MAX6635)
ALERT has programmable polarity and two modes:
comparator and interrupt. Polarity and mode are select-
ed through the Configuration register (Table 4). The
ALERT output is open drain.
Interrupt Mode
With ALERT in interrupt mode, the MAX6634/MAX6635
look for a THIGH or a TLOW fault. The ALERT pin asserts
an alarm for an undertemperature fault, as well as for
an overtemperature fault. Once either fault has
occurred, it remains active until deasserted by a read
of any register. The device then begins to look for a
temperature change crossing the hysteresis level. The
activation of ALERT is subject to the depth of the fault
queue.
For example: If THIGH is set to 100°C, THYST is set to
20°C, and the fault queue depth is set to 4, ALERT
does not assert until four consecutive conversions
exceed 100°C. If the temperature is then read through
the I2C-compatible interface, ALERT deasserts. ALERT
asserts again when four consecutive conversions are
less than 80°C.
Comparator Mode
In comparator mode, ALERT is asserted when the num-
ber of consecutive conversions exceeding the value in
the THIGH register, or lower than the value in the TLOW
register, is equal to the depth of the fault queue. ALERT
deasserts when the number of consecutive conversions
less than THIGH - THYST or greater than TLOW + THYST
is equal to the depth of the fault queue.
For example: If THIGH is set to 100°C, TLOW is set to
80°C, and the fault queue depth is set to four, ALERT
does not assert until four consecutive conversions
exceed 100°C, or are below 80°C. ALERT only
deasserts if four consecutive conversions are less than
THIGH - THYST or greater than TLOW + THYST.
Comparator mode allows autonomous clearing of an
ALERT fault without the intervention of a master and is
ideal to use for driving a thermostat (Figure 10).
Overtemperature Alarm (MAX6635)
The MAX6635 also includes an overtemperature output
that is always in comparator mode. Whenever the tem-
perature exceeds a value in the programmable TMAX
register, OVERT is asserted. OVERT only deasserts
after the temperature drops below TMAX - THYST. When
the fault queue is activated, OVERT is subject to that
queue, which sets the number of faults that must occur
before OVERT asserts or deasserts. This helps prevent
spurious alarms in noisy environments.
Comparator mode also allows autonomous clearing of
an OVERT fault without the intervention of a master and
thus is ideal to use for driving a cooling fan (Figure 11).
In this application, the polarity of OVERT is active high.
Shutdown
The MAX6633/MAX6634/MAX6635 feature a shutdown
mode, accessible through the serial interface that
saves power by turning off everything except the POR
MAX6633/MAX6634/MAX6635
12-Bit Plus Sign Temperature Sensors with
SMBus/I2C-Compatible Serial Interface
______________________________________________________________________________________ 11
3
8
VCC
+3V TO +5.5V
MAX6634
RELAY
5VDC, 20mA
125VAC, 1A
2N3904
HEATER
SUPPLY
HEATER
4
4kΩ
ALERT
Figure 10. Simple Thermostat
3
10kΩ
8
VCC
+3V TO +5.5V +12V
MAX6635
4
12V 300mA
MOTOR
FAN
LOGIC-LEVEL
MOSFET
OVERT
Figure 11. Fan Controller
MAX6633/MAX6634/MAX6635
and the serial interface. Enter shutdown by program-
ming the shutdown bit of the Configuration register
high. While in shutdown, the Temperature register
retains the last conversion result and can be read at
any time. The ADC is turned off, reducing the device
current draw to 30µA (max). The outputs of ALERT and
OVERT are latched upon entering shutdown, and the
fault queue is held in reset. After coming out of shut-
down, the Temperature register continues to read the
last converted temperature, until the next conversion
result is available.
Thermal Considerations
The MAX6633/MAX6634/MAX6635 supply current is
typically 200µA when the serial interface is inactive.
When used to drive high-impedance loads, the devices
dissipate negligible power; therefore, the die tempera-
ture is essentially the same as the package tempera-
ture. The key to accurate temperature monitoring is
good thermal contact between the MAX6633/MAX6634/
MAX6635 package and the monitored device or circuit.
Heat flows in and out of plastic packages primarily
through the leads. Short, wide copper traces leading to
the temperature monitor ensure that heat transfers
quickly and reliably. The rise in die temperature due to
self-heating is given by the following formula:
ΔTJ= PDISSIPATION x θJA
where PDISSIPATION is the power dissipated by the
MAX6633/MAX6634/MAX6635, and θJA is the pack-
age’s thermal resistance.
The typical thermal resistance is 170°C/W for the 8-pin
SO package. To limit the effects of self-heating, mini-
mize the output currents. For example, if the
MAX6634/MAX6635 sink 4mA with the maximum
ALERT VLspecification of 0.8V, an additional 3.2mW of
power is dissipated within the IC. This corresponds to a
0.54°C rise in the die temperature.
Applications Information
Figure 10 shows the MAX6634 used as a simple thermo-
stat to control a heating element. Figure 11 shows the
MAX6635 used as a temperature-triggered fan controller.
Chip Information
TRANSISTOR COUNT: 12,085
PROCESS: BiCMOS
12-Bit Plus Sign Temperature Sensors with
SMBus/I2C-Compatible Serial Interface
12 ______________________________________________________________________________________
MAX6633
A3 A2 A1 A0 ADDRESS
GND GND GND GND 1000 000
GND GND GND VCC 1000 001
GND GND VCC GND 1000 010
GND GND VCC VCC 1000 011
GND VCC GND GND 1000 100
GND VCC GND VCC 1000 101
GND VCC VCC GND 1000 110
GND VCC VCC VCC 1000 111
VCC GND GND GND 1001 000
VCC GND GND VCC 1001 001
VCC GND VCC GND 1001 010
VCC GND VCC VCC 1001 011
VCC VCC GND GND 1001 100
VCC VCC GND VCC 1001 101
VCC VCC VCC GND 1001 110
VCC VCC VCC VCC 1001 111
MAX6634
A2 A1 A0 ADDRESS
GND GND GND 1001 000
GND GND VCC 1001 001
GND VCC GND 1001 010
GND VCC VCC 1001 011
VCC GND GND 1001 100
VCC GND VCC 1001 101
VCC VCC GND 1001 110
VCC VCC VCC 1001 111
MAX6635
A1 A0 ADDRESS
GND GND 1001 000
GND VCC 1001 001
VCC GND 1001 010
VCC VCC 1001 011
Table 1. Address Selection
MAX6633/MAX6634/MAX6635
12-Bit Plus Sign Temperature Sensors with
SMBus/I2C-Compatible Serial Interface
______________________________________________________________________________________ 13
ADDRESS DESCRIPTION POR STATE
00h Temperature register
(READ only) 0000h
01h Configuration-Byte
register 00h
02h THYST register 0100h
03h TMAX register 2800h
04h TLOW register 0500h
05h THIGH register 2000h
Table 2. Pointer Register Bit
Assignments
D15 D14 D13 D12 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0
MSB
(Sign)
Bit
12
Bit
11
Bit
10 Bit 9 Bit 8 Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 TMAX THIGH TLOW
Table 3. Temperature Register
D7 D6 D5 D4 D3 D2 D1 D0
00
SMB Timeout
Disable
Fault Queue
Enable
ALERT
Polarity
OVERT
Polarity
Comparator
or Interrupt Shutdown
Table 4. Configuration Register
D15: MSB is the first sign bit.
D2, D1, D0: Flag bits for TMAX, THIGH, TLOW.
1LSB = 0.0625°C.
Temperature is stored in two’s complement format.
Power-on default = 0h.
D0: 0 = normal operation; 1 = shutdown.
D1: 0 = comparator mode; 1 = interrupt mode.
D2 to D3: 0 = active low; 1 = active high.
D5: 0 = normal SMBus operation; 1 = full I2C compatibility.
D7 to D6: Reserved locations, always write zeros.
MAX6633/MAX6634/MAX6635
D6 to D0: Reads all zeros, cannot be written.
1LSB = 1°C.
Power-On Default: THIGH = +64°C (2000h), TLOW = +10°C (0500h), TMAX = +80°C (2008h), THYST = 2°C (0100h).
12-Bit Plus Sign Temperature Sensors with
SMBus/I2C-Compatible Serial Interface
14 ______________________________________________________________________________________
D4 NO. OF FAULTS
0 1 (DEFAULT)
14
Table 5. Fault Queue Depth
D15 D14 D13 D12 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0
MSB
(Sign) Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 LSB 0000000
Table 7. THIGH, TLOW, TMAX, and THYST Registers
DIGITAL OUTPUT CODE
TEMP. (°C) BINARY HEX
MSB LSB
+150.0000 0100 1011 0000 0XXX 4B00
+125.0000 0011 1110 1000 0XXX 3E80
+25.0000 0000 1100 1000 0XXX 0C80
+0.0625 0000 0000 0000 1XXX 0008
0.0000 0000 0000 0000 0XXX 0000
-0.0625 1111 1111 1111 1XXX FFF8
-25.0000 1111 0011 0111 0XXX F370
-55.0000 1110 0100 0111 0XXX E470
Table 6. Output Code vs. Temperature
MAX6633/MAX6634/MAX6635
12-Bit Plus Sign Temperature Sensors with
SMBus/I2C-Compatible Serial Interface
______________________________________________________________________________________ 15
A1
A2GND
1
2
8
7
VCC
A0SCL
ALERT
SDA
SO
3
4
6
5
MAX6634
A1
GND
1
2
8
7
VCC
A0SCL
OVERT
SDA
SO
3
4
6
5
MAX6635
ALERT
A1
A2GND
1
2
8
7
VCC
A0SCL
A3
SDA
SO
3
4
6
5
MAX6633
TOP VIEW
Pin Configurations
MAX6633/MAX6634/MAX6635
12-Bit Plus Sign Temperature Sensors with
SMBus/I2C-Compatible Serial Interface
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
16
____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
© 2001 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
16
____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
© 2001 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.
Package Information
SOICN .EPS
PACKAGE OUTLINE, .150" SOIC
1
1
21-0041 B
REV.DOCUMENT CONTROL NO.APPROVAL
PROPRIETARY INFORMATION
TITLE:
TOP VIEW
FRONT VIEW
MAX
0.010
0.069
0.019
0.157
0.010
INCHES
0.150
0.007
E
C
DIM
0.014
0.004
B
A1
MIN
0.053A
0.19
3.80 4.00
0.25
MILLIMETERS
0.10
0.35
1.35
MIN
0.49
0.25
MAX
1.75
0.050
0.016L0.40 1.27
0.3940.386D
D
MINDIM
D
INCHES
MAX
9.80 10.00
MILLIMETERS
MIN MAX
16 AC
0.337 0.344 AB8.758.55 14
0.189 0.197 AA5.004.80 8
N MS012
N
SIDE VIEW
H 0.2440.228 5.80 6.20
e 0.050 BSC 1.27 BSC
C
HE
eBA1
A
D
0∞-8∞
L
1
VARIATIONS:
