Rainbow Electronics MAX6649 - Manual

General Description
The MAX6649 is a precise, two-channel digital temper-
ature sensor. It accurately measures the temperature of
its own die and a remote PN junction, and reports the
temperature in digital form using a 2-wire serial inter-
face. The remote PN junction 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
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 MAX6649 includes 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 MAX6649 provides 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 reg-
isters. The OVERT output can be used to activate a cool-
ing fan, or to trigger a system shutdown.
Measurements can be done autonomously, with the
conversion rate programmed by the user, or in a single-
shot mode. The adjustable conversion rate allows the
user to optimize supply current 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 MAX6649
operates from -55°C to +125°C, and measures tempera-
tures between 0°C and +145°C. The MAX6649 is avail-
able in an 8-pin µMAX package.
Applications
Graphics Processors
Desktop Computers
Notebook Computers
Servers
Thin Clients
Workstations
Test and Measurement
Multichip Modules
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)
♦ Two Alarm Outputs: ALERT and OVERT
♦ Programmable Under/Overtemperature Alarm
Temperature Thresholds
♦ Programmable Conversion Rate
♦ SMBus-Compatible Interface
♦ SMBus Timeout
MAX6649
+145°C Precision SMBus-Compatible Remote/
Local Sensor with Overtemperature Alarms
________________________________________________________________ Maxim Integrated Products 1
Ordering Information
V CC
DXP
DXN
10k Ω EACH
CLOCK
TO FAN DRIVER OR
SYSTEM SHUTDOWN
3.3V
DATA
INTERRUPTED TO µP
200 Ω 0.1 µF
SDA
SCLK
ALERT
GND
2200pF
µP
MAX6649
OVERT
Typical Operating Circuit
19-2540; Rev 0; 8/02
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.
PART TEMP RANGE
PIN-
PACKAGE MEASURED
TEMP RANGE
MAX6649MUA -55°C to +125°C 8 µMAX 0°C to +145°C
SMBus is a trademark of Intel Corp.
Pin Configuration and Functional Diagram appear at end of
data sheet.