Rainbow Electronics MAX6649 User Manual
General Description
The MAX6649 is a precise, two-channel digital temperature 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 interface. The remote PN junction is typically the emitterbase 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 registers. The OVERT output can be used to activate a cooling fan, or to trigger a system shutdown.
Measurements can be done autonomously, with the
conversion rate programmed by the user, or in a singleshot 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 temperatures between 0°C and +145°C. The MAX6649 is available 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
10kΩ EACH
CLOCK
TO FAN DRIVER OR
SYSTEM SHUTDOWN
3.3V
DATA
INTERRUPTED TO µP
200Ω
0.1µF
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-
MEASURED
TEMP RANGE
MAX6649MUA
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.
PACKAGE
-55°C to +125°C
MAX6649
+145°C Precision SMBus-Compatible Remote/
Local Sensor with Overtemperature Alarms
2 _______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
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.
All Voltages Referenced to GND
V
CC
...........................................................................-0.3V to +6V
DXP.............................................................-0.3V to (V
CC
+ 0.3V)
DXN .......................................................................-0.3V to +0.8V
SCLK, SDA, ALERT, OVERT.....................................-0.3V to +6V
SDA, ALERT, OVERT Current .............................-1mA to +50mA
DXN Current .......................................................................±1mA
Continuous Power Dissipation (T
A
= +70°C)
8-Pin µMAX (derate 5.9mW/°C above +70°C) .............471mW
ESD Protection (all pins, Human Body Model) ................±2000V
Junction Temperature......................................................+150°C
Operating Temperature Range .........................-55°C to +125°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
ELECTRICAL CHARACTERISTICS
(VCC= 3.0V to 5.5V, TA= -55°C to +125°C, unless otherwise specified. Typical values are at VCC= 3.3V and TA= +100°C.) (Note 1)
PARAMETER
CONDITIONS
UNITS
Supply Voltage V
CC
3.0 5.5 V
°C
Temperature Resolution
10 Bits
VCC = 3.3V,
T
A
= +100°C
0.5
VCC = 3.3V, TA =
Remote Temperature Error
V
CC
= 3.3V, TA =
+0°C to +100°C
°C
Local Temperature Error V
CC
= 3.3V
T
A
= 0°C to +125°C
°C
Supply Sensitivity of Temperature
Error
°C/V
Undervoltage Lockout (UVLO)
Threshold
UVLO Falling edge of V
CC
disables ADC 2.4 2.7
V
UVLO Hysteresis 90 mV
Power-On-Reset (POR) Threshold
VCC falling edge 2.0 V
POR Threshold Hysteresis 90 mV
Standby Supply Current SMBus static 3 12 µA
Operating Current During conversion
mA
0.25 conversions per second 40 80
Average Operating Current
2 conversions per second
400
µA
Conversion Time t
CONV
From stop bit to conversion completion 95
156 ms
Conversion Time Error -25
%
DXP and DXN Leakage Current Standby mode 100 nA
High level 80
120
Remote-Diode Source Current I
RJ
Low level 8 10 12
µA
SYMBOL
MIN TYP MAX
0.125
TRJ = +60°C to +145°C -1.0
+60°C to +100°C
T
= +25°C to +145°C -1.6 +1.6
RJ
TRJ = +0°C to +145°C -3.2 +3.2
TA = +60°C to +100°C -2.0 +2.0
-3.0 +3.0
±0.2
250
125
100
+1.0
2.95
0.08
+25
MAX6649
+145°C Precision SMBus-Compatible Remote/
Local Sensor with Overtemperature Alarms
_______________________________________________________________________________________ 3
ELECTRICAL CHARACTERISTICS (continued)
(VCC= 3.0V to 5.5V, TA= -55°C to +125°C, unless otherwise specified. Typical values are at VCC= 3.3V and TA= +100°C.) (Note 1)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
ALERT, OVERT
I
SINK
= 1mA 0.4
Output Low Voltage
I
SINK
= 4mA 0.6
V
Output High Leakage Current VOH = 5.5V 1 µA
SMBus-COMPATIBLE INTERFACE (SCLK AND SDA)
Logic Input Low Voltage V
IL
0.8 V
VCC = 3.0V 2.2
Logic Input High Voltage V
IH
VCC = 5.5V 2.6
V
Input Leakage Current I
LEAK
VIN = GND or V
CC
-1 +1 µA
Output Low-Sink Current I
SINK
VOL = 0.6V 6 mA
Input Capacitance C
IN
5pF
SMBus-COMPATIBLE TIMING (Note 2)
Serial Clock Frequency f
SCLK
(Note 3) 100 kHz
Bus Free Time Between STOP
and START Condition
t
BUF
4.7 µs
START Condition Setup Time 4.7 µs
Repeat START Condition Setup
Time
t
SU:STA
90% to 90% 50 ns
START Condition Hold Time
10% of SDA to 90% of SCLK 4 µs
STOP Condition Setup Time
90% of SCLK to 90% of SDA 4 µs
Clock Low Period t
LOW
10% to 10% 4.7 µs
Clock High Period t
HIGH
90% to 90% 4 µs
Data Setup Time
(Note 4) 250 µs
Receive SCLK/SDA Rise Time t
R
1µs
Receive SCLK/SDA Fall Time t
F
300 ns
Pulse Width of Spike Suppressed
t
SP
050ns
SMBus Timeout
SDA low period for interface reset 25 37 45 ms
Note 1: All parameters tested at a single temperature. Specifications over temperature are guaranteed by design.
Note 2: Timing specifications guaranteed by design.
Note 3: The serial interface resets when SCLK is low for more than t
TIMEOUT
.
Note 4: A transition must internally provide at least a hold time to bridge the undefined region (300ns max) of SCLK’s falling edge.
t
HD:STA
t
SU:STO
t
HD:DAT
t
TIMEOUT
MAX6649
+145°C Precision SMBus-Compatible Remote/
Local Sensor with Overtemperature Alarms
4 _______________________________________________________________________________________
Typical Operating Characteristics
(VCC= 3.3V, TA= +25°C, unless otherwise noted.)
MAX6649 toc01
SUPPLY VOLTAGE (V)
STANDBY SUPPLY CURRENT (µA)
5.04.54.03.5
3.0
3.5
4.0
4.5
5.0
2.5
3.0 5.5
STANDBY SUPPLY CURRENT
vs. SUPPLY VOLTAGE
MAX6649 toc02
CONVERSION RATE (Hz)
OPERATING SUPPLY CURRENT (µA)
4.002.001.000.500.250.13
100
200
300
400
0
0.63
OPERATING SUPPLY CURRENT
vs. CONVERSION RATE
MAX6649 toc03
TEMPERATURE (°C)
TEMPERATURE ERROR (°C)
125100755025
-1.5
-0.5
0
0.5
1.0
1.5
2.0
-2.0
0
REMOTE TEMPERATURE ERROR
vs. REMOTE-DIODE TEMPERATURE
-1.0
TA = +85°C
FAIRCHILD 2N3906
MAX6649 toc04
TEMPERATURE (°C)
TEMPERATURE ERROR (°C)
100755025
-1.5
-1.0
-0.5
0
0.5
1.0
-2.0
0 125
LOCAL TEMPERATURE ERROR
vs. DIE TEMPERATURE
MAX6649 toc05
FREQUENCY (Hz)
TEMPERATURE ERROR (°C)
10k1k100101
-1
0
1
2
3
4
5
-2
0.1 100k
VCC = SQUARE WAVE APPLIED TO
V
CC
WITH NO BYPASS CAPACITOR
LOCAL ERROR
TEMPERATURE ERROR
vs. POWER-SUPPLY NOISE FREQUENCY
REMOTE ERROR
MAX6649 toc06
FREQUENCY (Hz)
TEMPERATURE ERROR (°C)
10k1k10010
-1
0
1
2
3
4
5
6
7
8
9
-2
1 100k
LOCAL TEMPERATURE ERROR
vs. COMMON-MODE NOISE FREQUENCY
LOCAL ERROR
REMOTE ERROR
VIN = AC-COUPLED TO DXN
V
IN
= 100mV
P-P
MAX6649 toc07
FREQUENCY (Hz)
TEMPERATURE ERROR (°C)
10k1k10010
-0.5
0
0.5
1.0
1.5
2.0
-1.0
1 100k
TEMPERATURE ERROR
vs. DIFFERENTIAL-MODE NOISE FREQUENCY
MAX6649 toc08
DXP-DXN CAPACITANCE (nF)
TEMPERATURE ERROR (°C)
10.0001.000
-4
-3
-2
-1
0
1
-5
0.100 100.000
TEMPERATURE ERROR
vs. DXP-DXN CAPACITANCE
MAX6649
+145°C Precision SMBus-Compatible Remote/
Local Sensor with Overtemperature Alarms
_______________________________________________________________________________________ 5
Detailed Description
The MAX6649 is a temperature sensor designed to
work in conjunction with a microprocessor or other intelligence in thermostatic, process-control, or monitoring
applications. Communication with the MAX6649 occurs
through the SMBus-compatible serial interface and
dedicated alert pins. ALERT asserts if the measured
local or remote temperature is greater than the software-programmed ALERT high limit or less than the
ALERT low limit. ALERT also asserts if the remote-sensing diode pins are shorted or unconnected. The
overtemperature alarm, OVERT, asserts if the softwareprogrammed OVERT limit is exceeded. OVERT can be
connected to fans, a system shutdown, a clock throttle
control, or other thermal-management circuitry.
The MAX6649 converts temperatures to digital data
either at a programmed rate or in single conversions.
Temperature data is represented as 11 bits, with the
LSB equal to 0.125°C. The “main” temperature data registers (at addresses 00h and 01h) are 8-bit registers that
represent the data as 8 bits with the full-scale reading
indicating the diode fault status (Table 1). The remaining
3 bits of temperature data are available in the “extend-
ed” registers at addresses 11h and 10h (Table 2).
ADC and Multiplexer
The averaging ADC integrates over a 60ms period
(each channel, typically), with excellent noise rejection.
The multiplexer automatically steers bias currents
through the remote and local diodes. The ADC and
associated circuitry measure each diode’s forward voltage and compute the temperature based on this voltage. Both channels are automatically converted once
the conversion process has started, either in free-running or single-shot mode. If one of the two channels is
not used, the device still performs both measurements,
and the user can ignore the results of the unused channel. If the remote-diode channel is unused, connect
DXP to DXN rather than leaving the pins open.
Pin Description
PIN NAME FUNCTION
1V
CC
Supply Voltage Input, 3V to 5.5V. Bypass V
CC
to GND with a 0.1µF capacitor. A 200Ω series
resistor is recommended but not required for additional noise filtering.
2 DXP
Combined Remote-Diode Current Source and A/D Positive Input for Remote-Diode Channel. DO
NOT LEAVE DXP FLOATING; tie DXP to DXN if no remote diode is used. Place a 2200pF
capacitor between DXP and DXN for noise filtering.
3 DXN
Combined Remote-Diode Current Sink and A/D Negative Input. DXN is internally connected to
ground.
4 OVERT
Overtemperature Alert/Interrupt Output, Open Drain. OVERT is logic low when the temperature is
above the software-programmed threshold.
5 GND Ground
6 ALERT
SMBus Alert (Interrupt) Output, Open Drain. ALERT asserts when temperature exceeds user-set
limits (high or low temperature). ALERT stays asserted until acknowledged by either reading the
status register or by successfully responding to an alert response address, provided that the fault
condition no longer exists. See the
ALERT
Interrupts section.
7 SDA SMBus Serial-Data Input/Output, Open Drain
8 SCLK SMBus Serial-Clock Input
Table 1. Main Temperature Data Register
Format (00h, 01h)
TEMP (°C) DIGITAL OUTPUT
145 1001 0001
130 1000 0010
128 1000 0000
25 0001 1001
0 0000 0000
<0 0000 0000
Diode fault
(short or open)
1111 1111
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