Datasheet

high enough to provide the required measurement res-
olution. The interface for the MAX6672 requires a pullup
resistor.
Thermal Response Time
The time periods t
1
(low) and t
2
(high) are values that
are easily read by the µP timer/counter. The temperature
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.
Figure 1. PWM Waveform Timing
Table 1. Time Ratio vs. Temperature
TIME RATIO
(t
1
/t
2
)
TEMPERATURE
(°C)
0.936 125
0.878 100
0.807 70
0.714 30
0.646 0
0.602 -25
0.560 -40
t
2
t
1
TEMPERATURE
SENSOR
PWM
MODULATOR
DOUT
1
GND
3, 4
5
V
CC
t
2
t
1
www.maximintegrated.com
Maxim Integrated │ 5
MAX6672/MAX6673 PWM Output Temperature Sensors
in SC70 Packages
Chip Information
PROCESS: BiCMOS
Block Diagram