19-2545; Rev 1; 10/02
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
MAX6648/MAX6692
Ordering Information
PART
TEMP RANGE
PIN-
MEASURED
PACKAGE TEMP RANGE
0°C to +125°C
0°C to +125°C
0°C to +125°C
MAX6648MUA
-55°C to +125°C 8 µMAX
MAX6692MUA
-55°C to +125°C 8 µMAX
MAX6692MSA
-55°C to +125°C 8 SO
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
V
CC
DXP
10kΩ EACH
SDA
MAX6648
SCLK
MAX6692
ALERT
OVERT
GND
DATA
CLOCK
INTERRUPTED TO
µP
TO FAN DRIVER OR
SYSTEM SHUTDOWN
SMBus is a trademark of Intel Corp.
Pin Configuration and Functional Diagram appear at end of
data sheet.
1
________________________________________________________________
Maxim Integrated Products
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.
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
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
±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
I
RJ
High level
Low level
80
8
100
10
95
-25
2.0
90
3.5
0.45
40
250
125
12
0.8
80
400
156
+25
100
120
12
2.95
+0.8
+1.0
°C
+1.6
+3.0
+2.0
+3.0
°C
°C/V
V
mV
V
mV
µA
mA
µA
ms
%
nA
µA
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
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
Remote-Diode Source Current
V
CC
= 3.3V
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
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
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)
V
IL
V
IH
I
LEAK
I
SINK
C
IN
f
SCLK
t
BUF
(Note 3)
4.7
4.7
50
4
4
4.7
4
250
1
300
50
45
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
100
+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
kHz
µs
µs
ns
µs
µs
µs
µs
µs
µs
ns
ns
ms
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
MAX6648/MAX6692
SMBus-COMPATIBLE INTERFACE (SCLK AND SDA)
SMBus-COMPATIBLE TIMING
(Note 2)
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)
LOCAL TEMPERATURE ERROR
vs. DIE TEMPERATURE
MAX6648/92 toc04
TEMPERATURE ERROR
vs. POWER-SUPPLY NOISE FREQUENCY
MAX6648/92 toc05
TEMPERATURE ERROR
vs. COMMON-MODE NOISE FREQUENCY
8
TEMPERATURE ERROR (°C)
7
6
5
4
3
2
1
0
-1
-2
LOCAL ERROR
REMOTE ERROR
V
IN
= AC-COUPLED TO DXN
V
IN
= 100mV
P-P
MAX6648/92 toc06
1.0
0.8
TEMPERATURE ERROR (°C)
0.6
0.4
0.2
0
-0.2
-0.4
-0.6
-0.8
-1.0
0
25
50
75
100
1.6
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
REMOTE ERROR
LOCAL ERROR
9
125
100k
1
10
100
1k
10k
100k
TEMPERATURE (°C)
FREQUENCY (Hz)
FREQUENCY (Hz)
TEMPERATURE ERROR
vs. DIFFERENTIAL-MODE NOISE FREQUENCY
MAX6648/92 toc07
TEMPERATURE ERROR
vs. DXP-DXN CAPACITANCE
MAX6648/92 toc08
2.0
1.5
TEMPERATURE ERROR (°C)
1.0
0.5
0
-0.5
-1.0
-1.5
-2.0
1
10
100
1k
10k
V
IN
= 20mV
P-P
SQUARE WAVE
APPLIED TO DXP-DXN
1
0
TEMPERATURE ERROR (°C)
-1
-2
-3
-4
-5
-6
0.100
100k
1.000
10.000
100.000
FREQUENCY (Hz)
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 FLOATING;
tie 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
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