±9-254ꢂ; Rev 4; 7/±2
+145°C Precision SMBus-Compatible Remote/
Local Sensors with Overtemperature Alarms
7/MAX649
General Description
Features
The MAX6646/MAX6647/MAX6649 are precise, two-
channel digital temperature sensors. The devices accu-
rately measure the temperature of their own die and a
remote PN junction, and report the temperature in digital
form using a 2-wire serial interface. The remote PN junc-
tion is typically the emitter-base junction of a common-
collector PNP on a CPU, FPGA, or ASIC.
♦ Dual Channel: Measures Remote and Local
Temperature
♦ 0.125°C Resolution
♦ High Accuracy 1°C ꢀmaꢁx ꢂrom ꢃ+0°C to ꢃ1ꢄ5°C
ꢀRemotex, and 2°C ꢀmaꢁx ꢂrom ꢃ+0°C to ꢃ100°C
ꢀLocalx
The 2-wire serial interface accepts standard system man-
agement bus (SMBus) write byte, read byte, send byte,
and receive byte commands to read the temperature
data and to program the alarm thresholds. To enhance
system reliability, the MAX6646/MAX6647/MAX6649
include an SMBus timeout. A fault queue prevents the
ALERT and OVERT outputs from setting until a fault has
been detected one, two, or three consecutive times
(programmable).
♦ Measures High-Ideality Thermal Diodes Up to
ꢃ170°C ꢀApparentx
ꢃ1ꢄ5°C ꢀRealx
♦ Two Alarm Outputs: ALERT and OVERT
♦ Programmable Under/Overtemperature Alarm
Temperature Thresholds
♦ Programmable Conversion Rate
♦ SMBus-Compatible Interꢂace
♦ SMBus Timeout
The MAX6646/MAX6647/MAX6649 provide two system
alarms: ALERT and OVERT. ALERT asserts when any of
four temperature conditions are violated: local overtem-
perature, remote overtemperature, local undertempera-
ture, or remote undertemperature. OVERT asserts when
the temperature rises above the value in either of the two
OVERT limit registers. The OVERT output can be used to
activate a cooling fan, or to trigger a system shutdown.
Ordering Information
TEMP
RANGE PACKAGE
PIN-
MEASURED
TEMP RANGE
PART
Measurements can be done autonomously, at the pro-
grammed conversion rate, or in a single-shot mode. The
adjustable conversion rate allows optimizing supply cur-
rent and temperature update rate to match system needs.
-55°C to
8 μMAX
+125°C
MAX6646MUA+
MAX6647MUA+
MAX6649MUA+
0°C to +145°C
0°C to +145°C
0°C to +145°C
-55°C to
8 μMAX
+125°C
Remote accuracy is ±±1C maꢀimum error between ꢁ6ꢂ1C
and ꢁ±451C with no calibration needed. The MAX6646/
MAX6647/MAX6649 operate from -551C to ꢁ±251C, and
measure temperatures between ꢂ1C and ꢁ±451C. The
MAX6646/MAX6647/MAX6649 are available in an 8-pin
μMAX® package.
-55°C to
8 μMAX
+125°C
ꢁDenotes a lead(Pb)-free/RoHS-compliant package.
Typical Operating Circuit
Applications
3.3V
Graphics Processors
Desktop Computers
Notebook Computers
Servers
Thin Clients
0.1μF
200Ω
Workstations
V
CC
10kΩ EACH
Test and Measurement
Multichip Modules
MAX6646
MAX6647
MAX6649
DXP
DATA
SDA
CLOCK
SCLK
Selector Guide, Pin Conꢂigurations, and Functional Diagram
appear at end oꢂ data sheet.
ALERT
INTERRUPT TO μP
DXN
2200pF
OVERT
TO FAN DRIVER OR
SYSTEM SHUTDOWN
GND
μP
μMAX is a registered trademark of Maꢀim Integrated Products, Inc.
For pricing, delivery, and ordering inꢂormation, please contact Maꢁim Direct
at 1-888-+29-ꢄ+ꢄ2, or visit Maꢁim’s website at www.maꢁim-ic.com.
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