19-1836; Rev 2; 1/02
1°C Accurate Remote/Local Temperature
Sensor with SMBus Serial Interface
General Description
The MAX6654
†
is a precise digital thermometer that
reports the temperature of both a remote P-N junction
and its own die. The remote junction can be a diode-con-
nected transistor—typically a low-cost, easily mounted
2N3904 NPN type or 2N3906 PNP type—that replaces
conventional thermistors or thermocouples. Remote
accuracy is ±1°C for multiple transistor manufacturers,
with no calibration needed. The remote junction can also
be a common-collector PNP, such as a substrate PNP of
a microprocessor (µP).
The 2-wire serial interface accepts standard System
Management Bus (SMBus)
TM
, Write Byte, Read Byte,
Send Byte, and Receive Byte commands to program the
alarm thresholds and to read temperature data.
Measurements can be done automatically and
autonomously, with the conversion rate programmed by
the user, or programmed to operate in a single-shot
mode. The adjustable conversion rate allows the user to
optimize supply current and temperature update rate to
match system needs. When the conversion rate is faster
than 1Hz, the conversion results are available as a 7-bit-
plus-sign byte with a 1°C LSB. When the conversion rate
is 1Hz or slower, the MAX6654 enters the extended
mode. In this mode, 3 additional bits of temperature data
are available in the extended resolution register, provid-
ing 10-bit-plus-sign resolution with a 0.125°C LSB.
Single-shot conversions also have 0.125°C per LSB reso-
lution when the conversion rate is 1Hz or slower.
A parasitic resistance cancellation (PRC) mode can also
be invoked for conversion rates of 1Hz or slower by set-
ting bit 4 of the configuration register to 1. In PRC mode,
the effect of series resistance on the leads of the external
diode is canceled. The 11-bit conversion in PRC mode is
performed in <500ms and is disabled for conversion
rates faster than 1Hz. The one-shot conversion is also 11
bits in <500ms.
The MAX6654 default low-temperature measurement
limit is 0°C. This can be extended to -64°C by setting bit
5 of the configuration register to 1.
The MAX6654 is available in a small, 16-pin QSOP sur-
face-mount package.
Features
o
High Accuracy ±1°C (max) from +70°C to +100°C
(Remote)
o
11-Bit, 0.125°C Resolution
o
Dual Channel: Measures Remote and Local
Temperature
o
No Calibration Required
o
Programmable Under/Overtemperature Alarms
o
I
2
C™-Compatible/SMBus Interface
o
+3V to +5.5V Supply Range
MAX6654
Ordering Information
PART
MAX6654MEE
TEMP. RANGE
-55°C to +125°C
PIN-PACKAGE
16 QSOP
Typical Operating Circuit
0.1µF
200Ω
+3V TO +5V SUPPLY
CPU
V
CC
STBY
DXP
MAX6654
SMBCLK
SMBDATA
10k EACH
CLOCK
DATA
2200pF
DXN
ADD0 ADD1
ALERT
GND
INTERRUPT TO
µC
Pin Configuration
TOP VIEW
N.C. 1
V
CC
2
DXP 3
DXN 4
N.C. 5
ADD1 6
GND 7
GND 8
16 N.C.
15 STBY
14 SMBCLK
________________________Applications
Desktop Computers
Notebook Computers
Servers
Thin Clients
Workstations
Test and Measurement
Multichip Modules
MAX6654
13 N.C.
12 SMBDATA
11 ALERT
10 ADD0
9
N.C.
SMBus is a trademark of Intel Corp.
I
2
C is a trademark of Philips Corp.
†
Patents pending
QSOP
________________________________________________________________
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.
1°C Accurate Remote/Local Temperature
Sensor with SMBus Serial Interface
MAX6654
ABSOLUTE MAXIMUM RATINGS
(All voltages are referenced to GND unless otherwise noted.)
V
CC
..........................................................................-0.3V to +6V
DXP, ADD_ ................................................-0.3V to (VCC + 0.3V)
DXN ......................................................................-0.3V to +0.8V
SMBCLK, SMBDATA,
ALERT, STBY..
......................-0.3V to +6V
SMBDATA,
ALERT
Current .................................-1mA to +50mA
DXN Current ......................................................................±1mA
ESD Protection (all pins, Human Body Model). .................2000V
Continuous Power Dissipation (T
A
= +70°C)
16-Pin QSOP (derate 8.30mW/°C above +70°C).........667mW
Operating Temperature Range ........................-55°C to +125°C
Junction Temperature. .....................................................+150°C
Storage Temperature Range ............................-65°C to +165°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
= +3V to +5.5V, T
A
= -55°C to +125°C, unless otherwise noted. Typical values are at V
CC
= +3.3V and T
A
= +25°C.)
PARAMETER
SYMBOL
CONDITIONS
+60°C
≤
T
A
≤
+100°C, V
CC
= +3.3V
Accuracy (Local Sensor)
0°C
≤
T
A
≤
+100°C, V
CC
= +3.3V
-55°C
≤
T
A
≤
+120°C, V
CC
= +3.3V
+70°C
≤
T
RJ
≤
+100°C, V
CC
= +3.3V (Note 1)
Accuracy (Remote Sensor)
Line Regulation
Resolution (Legacy Mode)
Resolution (Extended Mode)
Undervoltage Lockout
Threshold
Undervoltage Lockout
Hysteresis
Supply Voltage Range
Power-On Reset (POR) Threshold
POR Threshold Hysteresis
Standby Current
Operating Current
Average Operating Current
Conversion Time
Conversion Timing Error
Remote Diode Current
I
RJ
High level
Low level
+80
+8
+100
+10
t
CONV
SMBus static
During conversion
0.25 conversion/s (Note 3)
2 conversion/s (Note 3)
From stop bit to conversion completed, in
legacy mode (Note 3)
+95
V
CC
V
CC
, falling edge
+3.0
+1.5
+2.0
+90
+3
+0.55
+40
+150
+125
+10
+1
+70
+250
+156
±25
+120
+12
UVLO
Conversion rate >1Hz
Conversion rate
≤1Hz
V
CC
input, disables A/D conversion,
rising edge
+1
+8
+0.125
+11
+2.60
+2.80
+90
+5.5
+2.5
+2.95
0°C
≤
T
RJ
≤
+100°C, V
CC
= +3.3V (Note 1)
-55°C
≤
T
RJ
≤
+120°C, V
CC
= +3.3V (Notes 1, 2)
MIN
-1.3
-2
-5
-1
-2
-5
0.2
TYP
MAX
+1.3
+2
+5
+1
+2
+5
0.5
°C
°C
Bits
°C
Bits
V
mV
V
V
mV
µA
mA
µA
ms
%
µA
°C
°C
UNITS
TEMPERATURE-TO-DIGITAL CONVERTER
2
_______________________________________________________________________________________
1°C Accurate Remote/Local Temperature
Sensor with SMBus Serial Interface
ELECTRICAL CHARACTERISTICS (continued)
(V
CC
= +3V to +5.5V, T
A
= -55°C to +125°C, unless otherwise noted. Typical values are at V
CC
= +3.3V and T
A
= +25°C.)
PARAMETER
Logic Input Low Voltage
Logic Input High Voltage
Input Leakage Current
Output Low Sink Current
Input Capacitance
Output High Leakage Current
Serial Clock Frequency
Bus Free Time Between STOP
and START Conditions
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
Data Hold Time
Receive SCL/SDA Rise Time
Receive SCL/SDA Fall Time
SMBus Timeout
t
SU:STA
t
HD:STA
t
SU:STO
t
LOW
t
HIGH
t
SU: DAT
t
HD: DAT
t
R
t
F
t
TIMEOUT
SMBDATA and SMBCLK time low for reset
of serial interface
+25
90% to 90%
10% of SMBDATA to 90% of SMBCLK
90% of SMBCLK to 10% of SMBDATA662
10% to 10%
90% to 90%
90% of SMBDATA to 10% of SMBCLK
(Note 5)
f
SCL
t
BUF
SYMBOL
V
IL
V
IH
I
LEAK
I
OL
C
in
V
OH
= +5.5V
(Note 4)
0
+4.7
+4.7
+50
+4
+4
+4.7
+4
+250
0
+1
+300
+40
V
CC
= +3.0V
V
CC
= +5.5V
V
IN
= GND or V
CC
V
OL
= +0.6V
V
OL
= +0.4V
+6
+1
+5
+1
+100
CONDITIONS
V
CC
= +3.0V to +5.5V
+2.2
+2.6
±2
MIN
TYP
MAX
+0.8
UNITS
V
V
µA
mA
pF
µA
kHz
µs
µs
µs
µs
µs
µs
µs
ns
µs
µs
ns
ms
MAX6654
Note 1:
+25°C
≤
T
A
≤
+85°C.
Note 2:
If both the MAX6654 and the remote junction are below T
A
= -20°C, then V
CC
> 3.15V.
Note 3:
The conversion time doubles for the extended resolution mode. This causes the average operating current to approximately
double.
Note 4:
The serial interface resets when SMBCLK is low for more than t
TIMEOUT
.
Note 5:
Note that a transition must internally provide at least a hold time to bridge the undefined region (300ns max) of SMBCLK’s
falling edge.
_______________________________________________________________________________________
3
1°C Accurate Remote/Local Temperature
Sensor with SMBus Serial Interface
MAX6654
Typical Operating Characteristics
(V
CC
= +3.3V to +5.5V, T
A
= +25°C, unless otherwise noted.)
TEMPERATURE ERROR vs.
REMOTE-DIODE TEMPERATURE
FAIRCHILD 2N3904
MAX6654 toc01
TEMPERATURE ERROR vs.
POWER-SUPPLY NOISE FREQUENCY
MAX6654 toc02
TEMPERATURE ERROR vs.
COMMON-MODE NOISE FREQUENCY
MAX6654 toc03
2
16
V
IN
= 500mVp-p LOCAL
TEMPERATURE ERROR (°C)
12
V
IN
= 500mVp-p REMOTE
8
3
TEMPERATURE ERROR (°C)
1
TEMPERATURE ERROR (°C)
2
0
1
-1
4
-2
-50 -30 -10 10 30 50 70 90 110 130 150
TEMPERATURE (°C)
0
1
100
10k
FREQUENCY (Hz)
1M
100M
0
1k
100k
FREQUENCY (Hz)
10M
TEMPERATURE ERROR vs.
DXP-DXN CAPACITANCE
V
CC
= +5V
7
TEMPERATURE ERROR (°C)
6
5
4
3
2
1
0
0
10 20 30 40 50 60 70 80 90 100
DXP-DXN CAPACITANCE (nF)
MAX6654 toc04
STANDBY SUPPLY CURRENT vs.
SUPPLY VOLTAGE
MAX6654 toc05
8
100
STANDBY SUPPLY CURRENT (µA)
90
80
70
60
50
40
3.0 3.2 3.4 3.6 3.8 4.0 4.2 4.4 4.6 4.8 5.0
SUPPLY VOLTAGE (V)
4
_______________________________________________________________________________________
1°C Accurate Remote/Local Temperature
Sensor with SMBus Serial Interface
Pin Description
PIN
1, 5, 9, 13, 16
2
3
4
6
7, 8
10
11
12
14
15
NAME
N.C.
V
CC
DXP
DXN
ADD1
GND
ADD0
ALERT
SMBDATA
SMBCLK
STBY
FUNCTION
No Connection. Not internally connected. May be used for PC board trace routing.
Supply Voltage Input. +3.0V to +5.5V. Bypass to GND with a 0.1µF capacitor. A 200Ω series
resistor is recommended but not required for additional noise filtering.
Combined Current Source and ADC Positive Input for Remote-Junction Channel. If a remote-
sensing junction is not used, connect DXP to DXN.
Combined Current Sink and ADC Negative Input. DXN is internally biased to a diode voltage above
ground.
SMBus Slave Address Select Input. ADD0 and ADD1 are sampled upon power-up.
Ground
SMBus Slave Address Select Input. ADD0 and ADD1 are sampled upon power-up.
SMBus Alert (Interrupt) Output. Open drain.
SMBus Serial-Data Input/Output. Open drain.
SMBus Serial-Clock Input
Hardware standby input. Temperature and comparison threshold data are retained in standby
mode. Low = standby mode, high = operating mode.
MAX6654
_______________________________________________________________________________________
5
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