MAX6646_07 Datasheet, PDF (1/16 Pages) Maxim Integrated Products – 145°C Precision SMBus-Compatible Remote/ Local Sensors with Overtemperature Alarms

19-2540; Rev 3; 5/07
+145°C Precision SMBus-Compatible Remote/
Local Sensors with Overtemperature Alarms
General Description
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.
The 2-wire serial interface accepts standard system man-
agement bus (SMBus^TM) 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 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.
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.
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.
Applications
Graphics Processors
Desktop Computers
Notebook Computers
Servers
Thin Clients
Workstations
Test and Measurement
Multichip Modules
SMBus is a trademark of Intel Corp.
µMAX is a registered trademark of Maxim Integrated Products, Inc.
Features
♦ Dual Channel: Measures Remote and Local
Temperature
♦ 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)
♦ Measures High-Ideality Thermal Diodes Up to
+170°C (Apparent)
+145°C (Real)
♦ 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
PIN-
PACKAGE
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
Typical Operating Circuit
0.1μF
3.3V
200Ω
V_CC
DXP ^MAX6646 SDA
MAX6647
MAX6649 _SCLK
DXN
2200pF
ALERT
OVERT
μP
GND
10kΩ EACH
DATA
CLOCK
INTERRUPT TO μP
TO FAN DRIVER OR
SYSTEM SHUTDOWN
Selector Guide, Pin Configurations, and Functional Diagram
appear at end of data sheet.
________________________________________________________________ Maxim Integrated Products 1
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