19-1495; Rev 1; 12/99
Remote Temperature Sensor
with SMBus Serial Interface
________________General Description
The MAX1618 precise digital thermometer reports the
temperature of a remote sensor. The remote sensor is a
diode-connected transistor—typically a low-cost, easily
mounted 2N3904 NPN type—that replaces conventional
thermistors or thermocouples. Remote accuracy is ±3°C
for multiple transistor manufacturers, with no calibration
needed. The MAX1618 can also measure the die temper-
ature of other ICs, such as microprocessors, that contain
an on-chip, diode-connected transistor.
The 2-wire serial interface accepts standard System
Management Bus (SMBus™) Write Byte, Read Byte, Send
Byte, and Receive Byte commands to program the alarm
thresholds and to read temperature data. The data format
is 7 bits plus sign, with each bit corresponding to 1°C, in
two’s complement format. Measurements can be done
automatically and autonomously, with the 16Hz conversion
rate or programmed to operate in a single-shot mode.
The thermostat mode configures the
ALERT
output as an
interrupt or as a temperature reset that remains active only
while the temperature is above the maximum temperature
limit or below the minimum temperature limit. The
ALERT
output polarity in thermostat mode can be configured for
active high or active low. Fan control is implemented using
this
ALERT
output.
The MAX1618 is available in a small (1.1mm high) 10-pin
µMAX package.
____________________________Features
o
Single Channel: Measures Remote CPU
Temperature
o
No Calibration Required
o
SMBus 2-Wire Serial Interface
o
Programmable Under/Overtemperature Alarms
o
Overtemperature Output for Fan Control
(Thermostat Mode)
o
Supports SMBus Alert Response Accuracy
±3°C (+60°C to +100°C)
±5°C (-55°C to +120°C)
o
3µA (typ) Standby Supply Current
o
900µA (max) Supply Current in Autoconvert Mode
o
+3V to +5.5V Supply Range
o
Small 10-Pin µMAX Package
MAX1618
†
Ordering Information
PART
MAX1618MUB
TEMP. RANGE
-55°C to +125°C
PIN-PACKAGE
10 µMAX
________________________Applications
Desktop and Notebook
Computers
Smart Battery Packs
LAN Servers
Industrial Controls
Central Office
Telecom Equipment
Test and Measurement
Multichip Modules
Typical Operating Circuit
0.1µF
3V TO 5.5V
200Ω
V
CC
STBY
10k EACH
___________________Pin Configuration
TOP VIEW
ADD0
1
ADD1
GND
DXN
DXP
2
3
4
5
10
ALERT
MAX1618
DXP
SMBCLK
SMBDATA
2N3904
DXN
2200pF
ALERT
CLOCK
DATA
INTERRUPT
TO
µC
9
SMBDATA
SMBCLK
STBY
V
CC
MAX1618
8
7
6
ADD0 ADD1 GND
µMAX
SMBus is a trademark of Intel Corp.
†Patents
Pending
________________________________________________________________
Maxim Integrated Products
1
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.
Remote Temperature Sensor
with SMBus Serial Interface
MAX1618
ABSOLUTE MAXIMUM RATINGS
V
CC
to GND ..............................................................-0.3V to +6V
DXP, ADD_ to GND ....................................-0.3V to (V
CC
+ 0.3V)
DXN to GND ..........................................................-0.3V to +0.8V
SMBCLK, SMBDATA,
ALERT, STBY
to GND ...........-0.3V to +6V
SMBDATA Current.................................................-1mA to 50mA
DXN Current. ......................................................................±1mA
ESD Protection (all pins, Human Body Model).. .............± 2000V
Continuous Power Dissipation (T
A
= +70°C)
µMAX (derate 5.6mW/°C above +70°C) ....................444mW
Operating Temperature Range (extended) ......-55°C to +125°C
Junction Temperature. ....................................................+150°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
= +3.3V, configuration byte register = X8h,
T
A
= 0°C to +85°C,
unless otherwise noted.)
PARAMETER
ADC AND POWER SUPPLY
Temperature Resolution
(Note 1)
Temperature Error,
Remote Diode (Note 2)
Supply-Voltage Range
Undervoltage Lockout
Threshold
Undervoltage Lockout Hysteresis
Power-On Reset Threshold
POR Threshold Hysteresis
Standby Supply Current
Standby Supply Current
Average Operating
Supply Current
Conversion Time
Conversion Rate Timing Error
Remote-Diode Source Current
DXN Source Voltage
ADDO, ADD1 Bias Current
SMBus INTERFACE
STBY
SMBCLK, SMBDATA
Input High Voltage
STBY
,
SMBCLK, SMBDATA
Input Low Voltage
STBY
,
SMBCLK, SMBDATA
Input Current
SMBCLK, SMBDATA
Output Low Sink Current
2
V
IH
V
IL
V
CC
= 3.0V
V
CC
= 3.0V to 5.5V
Logic inputs forced to V
CC
or GND
SMBCLK, SMBDATA forced to 0.4V
-1
6
2.2
0.8
1
V
V
µA
mA
Momentary upon power-on reset
t
CONV
SMBus static
Hardware or software standby,
SMBCLK at 10kHz
Autoconvert mode, average measured over
Autoconvert
4sec, 16 conv/sec
mode, average
From stop bit to conversion complete
Autoconvert mode
DXP forced to DXN + 0.65V,
ID = 1 (high)
High level
Low level
47
-25
80
8
100
10
0.7
160
V
CC
, falling edge
1
V
CC
UVLO
V
CC
input, disables A/D conversion,
rising edge
Monotonicity guaranteed
T
R
= +60°C to +100°C
T
R
= +55°C to +125°C
8
-3
-5
3
2.6
2.8
50
1.7
50
3
10
2.5
3
5
5.5
2.95
Bits
°C
V
V
mV
V
mV
µA
µA
900
78
25
120
12
µA
ms
%
µA
V
µA
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
5
450
62
_______________________________________________________________________________________
Remote Temperature Sensor
with SMBus Serial Interface
ELECTRICAL CHARACTERISTICS (continued)
(V
CC
= +3.3V, configuration byte register = X8h,
T
A
= 0°C to +85°C,
unless otherwise noted.)
PARAMETER
ALERT
Output Low Sink Current
ALERT
Output High
Leakage Current
SMBCLK, SMBDATA Input
Capacitance
SMBus Clock Frequency
SMBCLK Clock Low Time
SMBCLK Clock High Time
SMBCLK, SMBDATA Rise Time
SMBCLK, SMBDATA Fall Time
SMBus Start Condition
Setup Time
SMBus Repeated Start
Condition Setup Time
SMBus Start Condition
Hold Time
SMBus Stop Condition
Setup Time
SMBus Data Valid to SMBCLK
Rising-Edge Time
SMBus Data-Hold Time
SMBus Bus Free Time
SMBCLK Falling Edge to SMBus
Data-Valid Time
t
SU:STA
t
HD:STA
t
SU:STO
t
SU:DAT
t
HD:DAT
t
BUF
90% to 90% points
10% of SMBDATA to 90% of SMBCLK
90% of SMBCLK to 10% of SMBDATA
90% of SMBDATA to 10% of SMBCLK
(Note 4)
Between start/stop condition
Master clocking in data
t
LOW
t
HIGH
t
R
t
F
(Note 3)
10% to 10% points
90% to 90% points
10% to 90% points
90% to 10% points
4.7
500
4
4
250
0
4.7
1
4
1
300
DC
4.7
SYMBOL
CONDITIONS
ALERT
forced to 0.4V
ALERT
forced to 5.5V
5
100
MIN
6
1
TYP
MAX
UNITS
mA
µA
pF
kHz
µs
µs
µs
ns
µs
ns
µs
µs
ns
µs
µs
µs
MAX1618
ELECTRICAL CHARACTERISTICS
(V
CC
= +3.3V, configuration byte register = X8h,
T
A
= -55°C to +125°C,
unless otherwise noted.) (Note 5)
PARAMETER
Temperature Resolution (Note 1)
Initial Temperature Error,
Remote Diode (Note 2)
Supply-Voltage Range
Conversion Time
Conversion-Rate Timing Error
V
CC
t
CONV
From stop bit to conversion complete
Autoconvert mode
SYMBOL
CONDITIONS
Monotonicity guaranteed
T
R
= +60°C to +100°C
T
R
= -55°C to +125°C
MIN
8
-3
-5
3
47
-25
62
3
5
5.5
78
25
TYP
MAX
UNITS
Bits
°C
V
ms
%
_______________________________________________________________________________________
3
Remote Temperature Sensor
with SMBus Serial Interface
MAX1618
ELECTRICAL CHARACTERISTICS (continued)
(V
CC
= +3.3V, configuration byte register = X8h,
T
A
= -55°C to +125°C,
unless otherwise noted.) (Note 5)
PARAMETER
SMBus INTERFACE
STBY,
SMBCLK, SMBDATA
Input High Voltage
STBY,
SMBCLK, SMBDATA
Input Low Voltage
STBY,
SMBCLK, SMBDATA
Input Current
SMBCLK, SMBDATA Output
Low Sink Current
ALERT
Output Low Sink Current
ALERT
Output High Leakage
Current
V
CC
= 3.0V
V
CC
= 5.5V
V
CC
= 3.0V to 5.5V
Logic inputs forced to V
CC
or GND
SMBCLK, SMBDATA forced to 0.6V
ALERT
forced to 0.4V
ALERT
forced to 5.5V
-2
6
1
1
2.2
2.4
0.8
2
V
V
µA
mA
mA
µA
CONDITIONS
MIN
TYP
MAX
UNITS
Note 1:
Guaranteed, but not 100% tested.
Note 2:
A remote diode is any diode-connected transistor from Table 7. T
R
is the junction temperature of the remote diode. See
Remote Diode Selection
for remote-diode forward voltage requirements. Temperature specification guaranteed for a diode
with ideality factor (M
TR
= 1.013). Additional error = (1.013/M - 1)
✕
273 + Temp where M = Ideality of remote diode used.
Note 3:
The SMBus logic block is a static design that works with clock frequencies down to DC. While slow operation is possible, it
violates the 10kHz minimum clock frequency and SMBus specifications and may monopolize the bus.
Note 4:
Note that a transition must internally provide at least a hold time to bridge the undefined region (300ns max) of SMBCLK’s
falling edge.
Note 5:
Specifications from -55°C to +125°C are guaranteed by design, not production tested.
Typical Operating Characteristics
(T
A
= +25°C, unless otherwise noted.)
TEMPERATURE ERROR
vs. LEAKAGE RESISTANCE
MAX1618 toc01
TEMPERATURE ERROR
vs. REMOTE-DIODE TEMPERATURE
MAX1618 toc02
TEMPERATURE ERROR vs.
POWER-SUPPLY NOISE FREQUENCY
1
TEMPERATURE ERROR (°C)
0
-1
-2
-3
-4
-5
-6
V
IN
= 250mVp
-
p
V
IN
= 100mVp
-
p
MAX1618 toc03
40
30
TEMPERATURE ERROR (°C)
20
10
0
-10
-20
-30
-40
1
PATH = DXP TO GND AND CONFIG = H00
PATH = DXP TO GND AND CONFIG = H08
2.50
2.00
TEMPERATURE ERROR (°C)
1.50
1.00
0.50
0.00
CENTRAL CMPT3904
RANDOM SAMPLE
-55 -35 -15
5
25
45
65
2
PATH = DXP TO V
CC
(5.0V)
AND CONFIG = H08
PATH = DXP TO V
CC
(5.0V)
AND CONFIG = H00
10
LEAKAGE RESISTANCE (MΩ)
100
-0.50
-1.00
-7
85 105 125
-8
0.005
V
IN
= SQUARE WAVE APPLIED TO
V
CC
WITH NO 0.1µF V
CC
CAPACITOR
0.05
0.5
5
50
POWER-SUPPLY NOISE FREQUENCY (MHz)
TEMPERATURE (°C)
4
_______________________________________________________________________________________
Remote Temperature Sensor
with SMBus Serial Interface
____________________________Typical Operating Characteristics (continued)
(T
A
= +25°C, unless otherwise noted.)
TEMPERATURE ERROR vs.
COMMON-MODE NOISE FREQUENCY
MAX1618 toc04
MAX1618
TEMPERATURE ERROR
vs. DXP-DXN CAPACITANCE
V
CC
= 5V
MAX1618 toc05
MAX1618 toc08
120
100
TEMPERATURE ERROR (°C)
AC-COUPLED TO DXN
2200pF DXN-DXP CAPACITOR
V
IN
= 100mVp
-
p
0
80
60
40
V
IN
= 50mVp
-
p
20
0
10
100
COMMON-MODE NOISE FREQUENCY (MHz)
1000
TEMPERATURE ERROR (°C)
-10
-20
0
20
40
60
80
100
DXP-DXN CAPACITANCE (nF)
STANDBY SUPPLY CURRENT
vs. CLOCK FREQUENCY
MAX1618 toc06
50
STANDBY SUPPLY CURRENT (µA)
40
30
V
CC
= 5V
20
V
CC
= 3.3V
10
0
1
10
100
1000
CLOCK FREQUENCY (kHz)
STANDBY SUPPLY CURRENT
vs. SUPPLY VOLTAGE
90
STANDBY SUPPLY CURRENT (µA)
80
70
60
50
40
30
20
10
0
0
1
2
3
4
5
SUPPLY VOLTAGE (V)
ADD0, ADD1 = HIGH-Z
ADD0, ADD1 = GND
MAX1618 toc07
RESPONSE TO THERMAL SHOCK
120
110
100
TEMPERATURE (°C)
90
80
70
60
50
40
30
20
-2
0
2
4
6
8 10 12 14 16 18 20
TIME (sec)
10-PIN
µMAX
IMMERSED IN
+115°C FLUORINERT BATH
100
_______________________________________________________________________________________
5
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