19-2540; Rev 4; 7/12
+145°C Precision SMBus-Compatible Remote/
Local Sensors with Overtemperature Alarms
Features
The MAX6646/MAX6647/MAX6649 are precise, twochannel digital temperature sensors. The devices accurately 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 junction is typically the emitter-base junction of a commoncollector PNP on a CPU, FPGA, or ASIC.
♦ Dual Channel: Measures Remote and Local
Temperature
The 2-wire serial interface accepts standard system management 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).
The MAX6646/MAX6647/MAX6649 provide two system
alarms: ALERT and OVERT. ALERT asserts when any of
four temperature conditions are violated: local overtemperature, remote overtemperature, local undertemperature, 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.
Measurements can be done autonomously, at the programmed conversion rate, or in a single-shot mode. The
adjustable conversion rate allows optimizing supply current and temperature update rate to match system needs.
♦ Measures High-Ideality Thermal Diodes Up to
+170°C (Apparent)
+145°C (Real)
Remote accuracy is ±1°C maximum error between +60°C
and +145°C with no calibration needed. The MAX6646/
MAX6647/MAX6649 operate from -55°C to +125°C, and
measure temperatures between 0°C and +145°C. The
MAX6646/MAX6647/MAX6649 are available in an 8-pin
μMAX® package.
♦ 0.125°C Resolution
♦ High Accuracy ±1°C (max) from +60°C to +145°C
(Remote), and ±2°C (max) from +60°C to +100°C
(Local)
♦ Two Alarm Outputs: ALERT and OVERT
♦ Programmable Under/Overtemperature Alarm
Temperature Thresholds
♦ Programmable Conversion Rate
♦ SMBus-Compatible Interface
♦ SMBus Timeout
Ordering Information
PART
TEMP
RANGE
PINPACKAGE
MEASURED
TEMP RANGE
MAX6646MUA+
-55°C to
+125°C
8 μMAX
0°C to +145°C
MAX6647MUA+
-55°C to
+125°C
8 μMAX
0°C to +145°C
MAX6649MUA+
-55°C to
+125°C
8 μMAX
0°C to +145°C
+Denotes a lead(Pb)-free/RoHS-compliant package.
Typical Operating Circuit
Applications
Graphics Processors
Desktop Computers
Workstations
Notebook Computers
Test and Measurement
Servers
3.3V
Thin Clients
Multichip Modules
0.1μF
200Ω
VCC
DXP
Selector Guide, Pin Configurations, and Functional Diagram
appear at end of data sheet.
2200pF
μP
10kΩ EACH
MAX6646
MAX6647
MAX6649
SDA
SCLK
DATA
CLOCK
ALERT
INTERRUPT TO μP
OVERT
DXN
TO FAN DRIVER OR
SYSTEM SHUTDOWN
GND
μMAX is a registered trademark of Maxim Integrated Products, Inc.
For pricing, delivery, and ordering information, please contact Maxim Direct
at 1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
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MAX6646/MAX6647/MAX6649
General Description
