MAX6672_V01 datasheet(5/7 Pages) MAXIM

5 / 7 page

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 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

(t1/t2)

TEMPERATURE

(°C)

0.936

125

0.878

100

0.807

0.714

0.646

0.602

-25

0.560

-40

TEMPERATURE

SENSOR

PWM

MODULATOR

DOUT 1

GND

3, 4

VCC

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Maxim Integrated │ 5

MAX6672/MAX6673

PWM Output Temperature Sensors

in SC70 Packages

Chip Information

PROCESS: BiCMOS

Block Diagram

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