General Description
The MAX6672/MAX6673 are low-current temperature
sensors with a single-wire output. These temperature
sensors convert the ambient temperature into a 1.4kHz
PWM output, which contains the temperature informa-
tion in its duty cycle. The MAX6672 has an open-drain
output and the MAX6673 has a push-pull output.
The MAX6672/MAX6673 operate from 2.4V to 5.5V with
a maximum supply current of 150µA. Both devices fea-
ture a single-wire output that minimizes the number of
pins necessary to interface with a microprocessor.
The MAX6672/MAX6673 are available in 5-pin SC70
packages.
Applications
Industrial and Process Control
HVAC
Automotive
Environmental Control
Isolated Temperature Sensing
Features
♦Simple Single-Wire PWM Output
♦Tiny SC70 Package
♦Low 60µA (typ) Supply Current Consumption
♦1.4kHz Nominal Frequency
♦Choice of Outputs
Open Drain (MAX6672)
Push-Pull (MAX6673)
♦2.4V to 5.5V Supply Range
MAX6672/MAX6673
PWM Output Temperature Sensors
in SC70 Packages
________________________________________________________________ Maxim Integrated Products 1
N.C.
GNDGND
15VCC
DOUT
MAX6672
MAX6673
SC70
TOP VIEW
2
34
Pin Configuration
VCC
GND
GPIO TO CONTROL
SHUTDOWN
INPUT TO TIMER/
COUNTER
0.1µFMAX6672
MAX6673
µC
*
* PULLUP RESISTOR REQUIRED ONLY FOR THE MAX6672.
Typical Application Circuit
19-2458; Rev 0; 10/02
Ordering Information
PART TEMP RANGE PIN-
PACKAGE
TOP
MARK
M A X6 6 7 2AX K- T -40°C to +125°C 5 SC70-5 ACQ
M A X6 6 7 3AX K- T -40°C to +125°C 5 SC70-5 ACR
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.
MAX6672/MAX6673
PWM Output Temperature Sensors
in SC70 Packages
2 _______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
(VCC = 2.4V to 5.5V, TA= -40°C to +125°C, unless otherwise noted. Typical values specified at +25°C and VCC of 3.3V.) (Note 1)
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.
Note 1: All specifications are 100% tested at TA= +25°C. Specification limits over temperature (TA= -40°C to +125°C) are guaranteed
by design, not production tested.
Note 2: Temperature = -200 ✕ (0.85 - T1/T2)3 + (425 ✕ T1/T2) - 273. T1 is the low time period. T2 is the high time period (Figure 1).
Supply Voltage (VCC to GND) ................................. -0.3V to +6V
DOUT to GND (MAX6672)........................................-0.3V to +6V
DOUT to GND (MAX6673)..........................-0.3V to (VCC + 0.3V)
DOUT Short to GND ...................................................Continuous
ESD Protection (Human Body Model) ............................ ±2000V
Continuous Power Dissipation (TA= +70°C)
5-Pin SC70 (derate 2.5mW/°C above +70°C).............200mW
Operating Temperature Range .........................-40°C to +125°C
Storage Temperature Range .............................-65°C to +150°C
Junction Temperature......................................................+150°C
SC70 Package
Vapor Phase (60s) ...................................................... +215°C
Infrared (15s). ............................................................. +220°C
Lead Temperature (soldering, 10s) ................................ +300°C
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
TA = +25°C to +100°C-3 +3
TA = 0°C to +125°C-4 +4
TA = -20°C to +125°C-5 +5
Temperature Error
(Note 2) VCC = 3.3V
TA = -40°C to -20°C±3
°C
Nominal t1 Pulse Width 280 µs
Output Low Voltage VOL ISINK = 3mA 0.4 V
Output High Voltage VOH ISOURCE = 800µA (MAX6673) VCC - 0.5 V
Fall Time tFALL CLOAD = 100pF 14 ns
Rise Time tRISE CLOAD = 100pF (MAX6673) 96 ns
DOUT Open-Drain Leakage
Current VDOUT = 6V (MAX6672) 0.1 µA
Output Capacitance 2.5 pF
Power-Supply Rejection Ratio PSRR 2.4V to 5.5V, TA = -25°C to +125°C 0.3 0.8 °C/V
2.4V to 3.6V 60 100
Supply Current ICC 3.6V to 5.5V 70 150 µA
MAX6672/MAX6673
PWM Output Temperature Sensors
in SC70 Packages
_______________________________________________________________________________________ 3
Typical Operating Characteristics
(VCC = 3.3V, TA= +25°C, unless otherwise noted.)
1.00
1.25
1.50
1.75
2.00
OUTPUT FREQUENCY vs. TEMPERATURE
MAX6672 toc01
TEMPERATURE (°C)
FREQUENCY (kHz)
-50 25 50-25 0 75 100 125
1.010
1.005
1.000
0.995
0.990
2.0 3.52.5 3.0 4.0 4.5 5.0
NORMALIZED OUTPUT FREQUENCY
vs. SUPPLY VOLTAGE
MAX6672 toc02
SUPPLY VOLTAGE (V)
NORMALIZED FREQUENCY (kHz)
TA = +125°C
TA = +25°C
TA = -40°C
200
300
400
500
600
t1 AND t2 TIMES vs. TEMPERATURE
MAX6672 toc03
TEMPERATURE (°C)
t1 AND t2 TIMES (µs)
-50 25 50-25 0 75 100 125
t2
t1
-4
-2
0
2
4
OUTPUT ACCURACY vs. TEMPERATURE
MAX6672 toc04
TEMPERATURE (°C)
ACCURACY (°C)
-50 25 50-25 0 75 100 125
VCC = 3.3V
0
30
90
60
120
150
-50 0-25 25 50 75 100 125
SUPPLY CURRENT vs. TEMPERATURE
MAX6672 toc05
TEMPERATURE (°C)
SUPPLY CURRENT (µA)
VCC = 3.3V
VCC = 5V
50
60
80
70
90
100
2.0 3.02.5 3.5 4.0 4.5 5.0
SUPPLY CURRENT vs. SUPPLY VOLTAGE
MAX6672 toc06
SUPPLY VOLTAGE (V)
SUPPLY CURRENT (µA)
-1.0
-0.5
0
0.5
1.0
POWER-SUPPLY REJECTION
vs. TEMPERATURE
MAX6672 toc07
TEMPERATURE (°C)
POWER-SUPPLY REJECTION (°C/V)
-50 25 50-25 0 75 100 125
POWER-SUPPLY REJECTION
vs. FREQUENCY
MAX6672 toc08
FREQUENCY (Hz)
POWER-SUPPLY REJECTION (°C/V)
1.0
-1.0
0
0.5
-0.5
0.01 10 100 1k0.10 1 10k
VAC = 100mVP-P
0
30
90
60
120
150
OUTPUT RISE AND FALL TIMES
vs. CAPACITIVE LOAD
MAX6672 toc09
CAPACITIVE LOAD (nF)
OUTPUT RISE AND FALL TIMES (ns)
0.01 10.10 10
FALL TIME
MAX6673 RISE TIME
Detailed Description
The MAX6672/MAX6673 are low-current (60µA, typ),
local temperature sensors ideal for interfacing with µCs
or µPs. The MAX6672/MAX6673 convert their own tem-
perature into a ratiometric PWM output. The square-
wave output waveform time ratio contains the
temperature information. The output is a square wave
with a nominal frequency of 1.4kHz at +25°C. The tem-
perature is obtained with the following formula:
Temperature (°C) = -200 x(0.85 - t1 / t2)3
+ (425 xt1 / t2) - 273
Where t1is a fixed value and t2is modulated with the
temperature. Table 1 lists time ratio vs. temperature.
For temperatures greater than +50°C, the temperature
error is primarily first order and the following equation
can be used:
Temperature (°C) = (425 xt1 / t2) - 273
The MAX6673 has a push-pull output. The rise and fall
times of the MAX6673 output are negligible with
respect to the period; therefore, errors caused by
capacitive loading are minimized.
The output load capacitance should be minimized in
MAX6672 applications because the sourcing current is
set by the pullup resistor. If the output capacitance
becomes too large, unequal rise and fall times distort
the pulse width, thus delivering inaccurate readings.
Applications Information
Pulse-Width Modulation
Interfacing with a µC
The Typical Application Circuit shows the MAX6672/
MAX6673 interfaced with a µC. In this example, the
MAX6672/MAX6673 convert the ambient temperature
to a PWM waveform. The µC reads the temperature by
measuring the t1and t2periods in software and hard-
ware. The only timing requirements are that the clock
frequency used for timing measurements is stable and
084121620
THERMAL RESPONSE
IN STIRRED OIL BATH
MAX6672 toc10
TIME (s)
TEMPERATURE (°C)
25
50
75
100
TRANSITION FROM +25°C AIR
TO +100°C STIRRED OIL BATH
0
10
5
20
15
25
30
-50 0-25 25 50 75 100 125
OUTPUT SINK CURRENT
vs. TEMPERATURE
MAX6672 toc11
TEMPERATURE (°C)
SINK CURRENT (mA)
VOL = 0.4V
VCC = 3.3V
VCC = 5V
0
1.0
0.5
2.0
1.5
2.5
3.0
-50 0-25 25 50 75 100 125
MAX6673 OUTPUT SOURCE CURRENT
vs. TEMPERATURE
MAX6672 toc12
TEMPERATURE (°C)
SOURCE CURRENT (mA)
VOH = VCC - 0.5V
VCC = 3.3V
VCC = 5V
MAX6672/MAX6673
PWM Output Temperature Sensors
in SC70 Packages
4 _______________________________________________________________________________________
Typical Operating Characteristics (continued)
(VCC = 3.3V, TA= +25°C, unless otherwise noted.)
PIN NAME FUNCTION
1 DOUT Digital Output Pin. PWM output, open-drain output (MAX6672), or push-pull output (MAX6673).
2 N.C. No Connection. Not internally connected.
3, 4 GND Pin 3 and Pin 4 must be tied together and connected to ground.
5V
CC Positive Supply. Bypass with a 0.1µF capacitor to GND.
Pin Description
MAX6672/MAX6673
PWM Output Temperature Sensors
in SC70 Packages
_______________________________________________________________________________________ 5
high enough to provide the required measurement res-
olution. The interface for the MAX6672 requires a pullup
resistor.
Thermal Response Time
The time periods t1(low) and t2(high) are values that
are easily read by the µP timer/counter. The tempera-
ture reading is then calculated using software. Since
both periods are obtained consecutively, using the
same clock, performing the division indicated in the
above formulae results in a ratiometric value that is
independent of the exact frequency.
Sensing Circuit Board and Ambient
Temperatures
Temperature sensor ICs such as the MAX6672/
MAX6673 that sense their own die temperatures must
be mounted on or close to the object whose tempera-
ture they are intended to measure. Because there is a
good thermal path between the SC70 package’s metal
leads and the IC die, the MAX6672/MAX6673 can
accurately measure the temperature of the circuit
board to which they are soldered. If the sensor is
intended to measure the temperature of a heat-generat-
ing component on the circuit board, it should be mount-
ed as close as possible to that component and should
share supply and ground traces (if they are not noisy)
with that component where possible. This maximizes
the heat transfer from the component to the sensor.
The thermal path between the plastic package and the
die is not as good as the path through the leads, so the
MAX6672/MAX6673, like all temperature sensors in
plastic packages, are less sensitive to the temperature
of the surrounding air than they are to the temperature
of their leads. They can be successfully used to sense
ambient temperature if the circuit board is designed to
track the ambient temperature.
As with any IC, the wiring and circuits must be kept
insulated and dry to avoid leakage and corrosion,
especially if the part is operated at cold temperatures
where condensation can occur.
The error caused by power dissipation in the MAX6672/
MAX6673 is negligible.
Chip Information
TRANSISTOR COUNT: 601
PROCESS: BiCMOS
Table 1. Time Ratio vs. Temperature
TIME RATIO
(t1/t2)
TEMPERATURE
(°C)
0.936 125
0.878 100
0.807 70
0.714 30
0.646 0
0.602 -25
0.560 -40
t2t1
Figure 1. PWM Waveform Timing
Block Diagram
t2t1
TEMPERATURE
SENSOR
PWM
MODULATOR
DOUT 1
GND
3, 4
5
VCC
SC70, 5L.EPS
MAX6672/MAX6673
PWM Output Temperature Sensors
in SC70 Packages
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
6_____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
© 2002 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.
Package Information
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information,
go to www.maxim-ic.com/packages.)
