Rainbow Electronics MAX6577 - Manual (Page 5)

Applications Information
Quick-Look Circuits
Figure 3 shows a quick-look application circuit for the
MAX6576 using a universal counter measuring period.
TS1 and TS0 are both tied to ground to select a scalar
multiplier of 10µs/°K. The MAX6576 converts the ambi-
ent temperature into a square wave with a period that is
10 times the absolute temperature of the device in µs.
At room temperature, the universal counter will display
approximately 2980µs.
Figure 4 shows a quick-look application circuit for the
MAX6577 using a universal counter measuring frequen-
cy. TS1 is tied to ground and TS0 is tied to V
DD to
select a scalar multiplier of 1Hz/°K. The MAX6577 con-
verts the ambient temperature into a square wave with
a frequency that is equal to the absolute temperature of
the device in Hertz. At room temperature, the universal
counter will display approximately 298Hz.
Interfacing with a Microcontroller
Figure 5 shows the MAX6577 interfaced with an 8051
µC. In this example, TS1 is tied to ground and TS0 is
tied to V DD to select a scalar multiplier of 1Hz/°K. The
MAX6577 converts the ambient temperature into a
square wave with a frequency that is equal to the
absolute temperature of the device in Hertz. The 8051
µC reads the frequency of the square-wave output of
the MAX6577 into Timer 0 and displays the temperature
as degrees Celsius in binary on Port 1. Listing 1 pro-
vides the code for this application. The interface is simi-
lar for the MAX6576, except the µC will perform a
period measurement.
Noise Considerations
The accuracy of the MAX6576/MAX6577 is susceptible
to noise generated both internally and externally. The
effects of external noise can be minimized by placing a
0.1µF ceramic bypass capacitor close to the supply pin
of the devices. Internal noise is inherent in the opera-
tion of the devices and is detailed in Table 3. Internal
averaging minimizes the effect of this noise when using
longer scalar timeout multipliers. The effects of this noise
are included in the overall accuracy of the devices as
specified in the
Electrical Characteristics .
MAX6576/MAX6577
SOT Temperature Sensors with
Period/Frequency Output
_______________________________________________________________________________________ 5
t OUT
MAX6576
CLOCK WAVEFORM OUTPUT
t
OUT
f
OUT
= 1 / t
OUT
f
OUT
(°K)
MAX6577
CLOCK WAVEFORM OUTPUT
Figure 1. MAX6576 Timing Diagram Figure 2. MAX6577 Timing Diagram