19-2545; Rev 4; 6/08
Precision SMBus-Compatible Remote/Local
Temperature Sensors with Overtemperature Alarms
General Description
The MAX6648/MAX6692 are precise, two-channel digi-
tal temperature sensors. They 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 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 MAX6648/MAX6692
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 MAX6648/MAX6692 provide two system alarms:
ALERT
and
OVERT. ALERT
asserts when any of four tem-
perature conditions are violated: local overtemperature,
remote overtemperature, local undertemperature, or
remote undertemperature.
OVERT
asserts when the tem-
perature 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 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 ±0.8°C maximum error between
+25°C and +125°C with no calibration needed. The
MAX6648/MAX6692 operate from -55°C to +125°C, and
measure temperatures between 0°C and +125°C. The
MAX6648 is available in an 8-pin µMAX
®
package, and the
MAX6692 is available in 8-pin µMAX and SO packages.
Features
o
Dual Channel Measures Remote and Local
Temperature
o
+0.125°C Resolution
o
High Accuracy ±0.8°C (max) from +25°C to +125°C
(Remote), and ±2°C (max) from +60°C to +100°C
(Local)
o
Two Alarm Outputs:
ALERT
and
OVERT
o
Two Default
OVERT
Thresholds Available
MAX6648: +110°C
MAX6692: +85°C
o
Programmable Conversion Rate
o
SMBus-Compatible Interface
o
SMBus Timeout
o
Programmable Under/Overtemperature Alarm
Thresholds
o
Compatible with 90nm, 65nm, and 45nm Process
Technology
MAX6648/MAX6692
Ordering Information
PART
MAX6648MUA
MAX6648YMUA
MAX6692MUA
MAX6692MSA
MAX6692YMUA
MAX6692YMSA
PIN-
PACKAGE
8 µMAX
8 µMAX
8 µMAX
8 SO
8 µMAX
8 SO
MEASURED
TEMP RANGE
0°C to +125°C
0°C to +125°C
0°C to +125°C
0°C to +125°C
0°C to +125°C
0°C to +125°C
Note:
All devices operate over the -55°C to +125°C temperature
range.
Typical Operating Circuit
3.3V
0.1μF
200Ω
Applications
Desktop Computers
Notebook Computers
Servers
Thin Clients
Workstations
Test and Measurement
Multichip Modules
μP
2200pF
DXN
GND
DXP
V
CC
10kΩ EACH
SDA
DATA
CLOCK
INTERRUPTED TO
μP
TO FAN DRIVER OR
SYSTEM SHUTDOWN
MAX6648
SCLK
MAX6692
ALERT
OVERT
SMBus is a trademark of Intel Corp.
µMAX is a registered trademark of Maxim Integrated Products, Inc.
Pin Configuration and Functional Diagram appear at end of
data sheet.
1
________________________________________________________________
Maxim Integrated Products
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.
Precision SMBus-Compatible Remote/Local
Temperature Sensors with Overtemperature Alarms
MAX6648/MAX6692
ABSOLUTE MAXIMUM RATINGS
(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
8-Pin SO (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
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.
ELECTRICAL CHARACTERISTICS
(V
CC
= 3.0V to 5.5V, T
A
= -55°C to +125°C, unless otherwise specified. Typical values are at V
CC
= 3.3V and T
A
= +85°C.) (Note 1)
PARAMETER
Supply Voltage
Temperature Resolution
V
CC
= 3.3V,
T
A
= +85°C
Remote Temperature Error
n = 1.008
V
CC
= 3.3V,
+60°C
≤
T
A
≤
+100°C
T
RJ
= +25°C to +125°C
T
RJ
= +60°C to +100°C
T
RJ
= 0°C to +125°C
SYMBOL
V
CC
CONDITIONS
MIN
3.0
0.125
10
-0.8
-1.0
-1.6
-3.0
-2.0
-3.0
-4.0
-4.4
±0.2
UVLO
Falling edge of V
CC
disables ADC
2.4
2.7
90
V
CC
falling edge
SMBus static
During conversion
0.25 conversions per second
2 conversions per second
t
CONV
From stop bit to conversion completion
Standby mode
95
-25
2.0
90
3.5
0.45
40
250
125
12
0.8
80
400
156
+25
100
2.95
+0.8
+1.0
°C
+1.6
+3.0
+2.0
+3.0
°C
°C
°C/V
V
mV
V
mV
µA
mA
µA
ms
%
nA
TYP
MAX
5.5
UNITS
V
°C
Bits
V
CC
= 3.3V, +0°C
T
RJ
= 0°C to +125°C
≤
T
A
≤
+100°C
Local Temperature Error
Local Temperature Error
(MAX6648Y/MAX6692Y)
Supply Sensitivity of Temperature
Error
Undervoltage Lockout (UVLO)
Threshold
UVLO Hysteresis
Power-On-Reset (POR) Threshold
POR Threshold Hysteresis
Standby Supply Current
Operating Current
Average Operating Current
Conversion Time
Conversion Time Error
DXP and DXN Leakage Current
V
CC
= 3.3V
V
CC
= 3.3V
T
A
= +60°C to +100°C
T
A
= 0°C to +125°C
T
A
= +60°C to +100°C
T
A
= 0°C to +125°C
2
_______________________________________________________________________________________
Precision SMBus-Compatible Remote/Local
Temperature Sensors with Overtemperature Alarms
ELECTRICAL CHARACTERISTICS (continued)
(V
CC
= 3.0V to 5.5V, T
A
= -55°C to +125°C, unless otherwise specified. Typical values are at V
CC
= 3.3V and T
A
= +85°C.) (Note 1)
PARAMETER
Remote-Diode Source Current
ALERT, OVERT
Output Low Voltage
Output High Leakage Current
Logic Input Low Voltage
Logic Input High Voltage
Input Leakage Current
Output Low-Sink Current
Input Capacitance
SMBus-COMPATIBLE TIMING
(Note 2)
Serial Clock Frequency
Bus Free Time Between STOP and
START Condition
START Condition Setup Time
Repeat START Condition Setup
Time
START Condition Hold Time
STOP Condition Setup Time
Clock Low Period
Clock High Period
Data Setup Time
Receive SCLK/SDA Rise Time
Receive SCLK/SDA Fall Time
Pulse Width of Spike Suppressed
SMBus Timeout
t
SU:STA
t
HD:STA
t
SU:STO
t
LOW
t
HIGH
t
HD:DAT
t
R
t
F
t
SP
t
TIMEOUT
SDA low period for interface reset
0
25
37
90% to 90%
10% of SDA to 90% of SCLK
90% of SCLK to 90% of SDA
10% to 10%
90% to 90%
(Note 4)
f
SCLK
t
BUF
(Note 3)
4.7
4.7
50
4
4
4.7
4
250
1
300
50
55
100
kHz
µs
µs
ns
µs
µs
µs
µs
µs
µs
ns
ns
ms
V
IL
V
IH
I
LEAK
I
SINK
C
IN
V
CC
= 3.0V
V
CC
= 5.5V
V
IN
= GND or V
CC
V
OL
= 0.6V
2.2
2.6
-1
6
5
+1
I
SINK
= 1mA
I
SINK
= 4mA
V
OH
= 5.5V
0.4
0.6
1
0.8
V
µA
V
V
µA
mA
pF
SYMBOL
I
RJ
High level
Low level
CONDITIONS
MIN
80
8
TYP
100
10
MAX
120
12
UNITS
µA
MAX6648/MAX6692
SMBus-COMPATIBLE INTERFACE (SCLK AND SDA)
Note 1:
Note 2:
Note 3:
Note 4:
All parameters tested at a single temperature. Specifications over temperature are guaranteed by design.
Timing specifications guaranteed by design.
The serial interface resets when SCLK is low for more than t
TIMEOUT
.
A transition must internally provide at least a hold time to bridge the undefined region (300ns max) of SCLK’s falling edge.
_______________________________________________________________________________________
3
Precision SMBus-Compatible Remote/Local
Temperature Sensors with Overtemperature Alarms
MAX6648/MAX6692
Typical Operating Characteristics
(V
CC
= 3.3V, T
A
= +25°C, unless otherwise noted.)
STANDBY SUPPLY CURRENT
vs. SUPPLY VOLTAGE
MAX6648/92 toc01
OPERATING SUPPLY CURRENT
vs. CONVERSION RATE
MAX6648/92 toc02
REMOTE TEMPERATURE ERROR
vs. REMOTE-DIODE TEMPERATURE
MAX6648/92 toc03
4.0
STANDBY SUPPLY CURRENT (μA)
600
OPERATING SUPPLY CURRENT (μA)
500
400
300
200
100
0
2.5
3.6
TEMPERATURE ERROR (°C)
1.5
0.5
3.2
-0.5
2.8
-1.5
T
A
= +85°C
FAIRCHILD 2N3906
-2.5
0.63
0.13 0.25 0.50 1.00
CONVERSION RATE (Hz)
2.00
4.00
0
25
50
75
100
125
TEMPERATURE (°C)
2.4
3.0
3.5
4.0
4.5
5.0
5.5
SUPPLY VOLTAGE (V)
REMOTE TEMPERATURE ERROR
vs. 45nm REMOTE DIODE TEMPERATURE
MAX6648/92 toc04
LOCAL TEMPERATURE ERROR
vs. DIE TEMPERATURE
MAX6648/92 toc05
TEMPERATURE ERROR
vs. POWER-SUPPLY NOISE FREQUENCY
1.4
TEMPERATURE ERROR (°C)
1.2
1.0
0.8
0.6
0.4
0.2
0
V
IN
= SQUARE WAVE APPLIED TO V
CC
WITH NO 0.1μF V
CC
CAPACITOR
0.1
1
10
100
1k
10k
100k
REMOTE ERROR
LOCAL ERROR
MAX6648/92 toc06
6
4
TEMPERATURE ERROR (°C)
2
0
-2
-4
-6
50
60
70
80
90
1.0
0.8
TEMPERATURE ERROR (°C)
0.6
0.4
0.2
0
-0.2
-0.4
-0.6
-0.8
-1.0
1.6
100
0
25
50
75
100
125
TEMPERATURE (°C)
TEMPERATURE (°C)
FREQUENCY (Hz)
TEMPERATURE ERROR
vs. COMMON-MODE NOISE FREQUENCY
8
TEMPERATURE ERROR (°C)
7
6
5
4
3
2
1
0
-1
-2
1
10
100
1k
10k
100k
FREQUENCY (Hz)
LOCAL ERROR
REMOTE ERROR
V
IN
= AC-COUPLED TO DXN
V
IN
= 100mV
P-P
MAX6648/92 toc07
TEMPERATURE ERROR
vs. DIFFERENTIAL-MODE NOISE FREQUENCY
1.5
TEMPERATURE ERROR (°C)
1.0
0.5
0
-0.5
-1.0
-1.5
-2.0
1
10
100
1k
10k
100k
FREQUENCY (Hz)
V
IN
= 20mV
P-P
SQUARE WAVE
APPLIED TO DXP-DXN
MAX6648/92 toc08
TEMPERATURE ERROR
vs. DXP-DXN CAPACITANCE
MAX6648/92 toc09
9
2.0
1
0
TEMPERATURE ERROR (°C)
-1
-2
-3
-4
-5
-6
0.100
1.000
10.000
100.000
DXP-DXN CAPACITANCE (nF)
4
_______________________________________________________________________________________
Precision SMBus-Compatible Remote/Local
Temperature Sensors with Overtemperature Alarms
Pin Description
PIN
1
NAME
V
CC
FUNCTION
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.
Combined Remote-Diode Current Source and A/D Positive Input for Remote-Diode Channel.
DO
NOT LEAVE DXP DISCONNECTED;
connect DXP to DXN if no remote diode is used. Place a
2200pF capacitor between DXP and DXN for noise filtering.
Combined Remote-Diode Current Sink and A/D Negative Input. DXN is internally biased to one
diode drop above ground.
Overtemperature Alert/Interrupt Output, Open Drain.
OVERT
is logic low when the temperature is
above the software-programmed threshold.
Ground
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.
SMBus Serial-Data Input/Output, Open Drain
SMBus Serial-Clock Input
MAX6648/MAX6692
2
DXP
3
4
5
DXN
OVERT
GND
6
ALERT
7
8
SDA
SCLK
Detailed Description
The MAX6648/MAX6692 are temperature sensors
designed to work in conjunction with a microprocessor
or other intelligence in thermostatic, process-control, or
monitoring applications. Communication with the
MAX6648/MAX6692 occurs through the SMBus-com-
patible 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 software-programmed
OVERT
limit is
exceeded.
OVERT
can be connected to fans, a system
shutdown, a clock throttle control, or other thermal-
management circuitry.
The MAX6648/MAX6692 convert temperatures to digital
data either at a programmed rate or in single conver-
sions. Temperature data is represented as 10 bits plus
sign, with the LSB equal to 0.125°C. The “main” tempera-
ture data registers (at addresses 00h and 01h) are 8-bit
registers that represent the data as 7 bits with the final
MSB indicating the diode fault status (Table 1). The
remaining 3 bits of temperature data are available in the
“extended” 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 volt-
age and compute the temperature based on this volt-
age. Both channels are automatically converted once
the conversion process has started, either in free-run-
ning 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 chan-
Table 1. Main Temperature Data Register
Format (00h, 01h)
TEMP (°C)
130
127
126
25
0
<0
-1
-25
Diode fault
(short or open)
DIGITAL OUTPUT
0 111 1111
0 111 1111
0 111 1111
0 001 1001
0 000 0000
0 000 0000
0 000 0000
0 000 0000
1 000 0000
_______________________________________________________________________________________
5
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