MAX6672 MAXIM [Maxim Integrated Products], MAX6672 Datasheet - Page 5

• Manufacturer Part Number: MAX6672
• Description: PWM Output Temperature Sensors in SC70 Packages
• Manufacturer: MAXIM [Maxim Integrated Products]

Table 1. Time Ratio vs. Temperature
high enough to provide the required measurement res-
olution. The interface for the MAX6672 requires a pullup
resistor.
The time periods t
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.
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.
TIME RATIO
Sensing Circuit Board and Ambient
(t
0.936
0.878
0.807
0.714
0.646
0.602
0.560
1
/t
2
)
_______________________________________________________________________________________
1
(low) and t
Thermal Response Time
2
PWM Output Temperature Sensors
(high) are values that
TEMPERATURE
Temperatures
(°C)
125
100
-25
-40
70
30
0
Figure 1. PWM Waveform Timing
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.
TRANSISTOR COUNT: 601
PROCESS: BiCMOS
TEMPERATURE
SENSOR
3, 4
in SC70 Packages
GND
5
V
CC
MODULATOR
PWM
t
2
Chip Information
Block Diagram
DOUT 1
t
t
1
2
t
1
5