tc72-5.0mmf Microchip Technology Inc., tc72-5.0mmf Datasheet - Page 13

• Manufacturer Part Number: tc72-5.0mmf
• Description: Digital Temperature Sensor With Spi? Interface
• Manufacturer: Microchip Technology Inc.

TC72
5.0
APPLICATIONS INFORMATION
The TC72 does not require any additional components
in order to measure temperature; however, it is recom-
mended that a decoupling capacitor of 0.1mF to 1mF
be provided between the V
and GND pins. Although
DD
the current consumption of the TC72 is modest
(250 mA, typical), the TC72 contains an on chip data
acquisition with internal digital switching circuitry. Thus,
it is considered good design practice to use an external
decoupling capacitor with the sensor. A high frequency
ceramic capacitor should be used and be located as
close as possible to the IC power pins in order to
provide effective noise protection to the TC72.
The TC72 measures temperature by monitoring the
voltage of a diode located on the IC die. The IC pins of
the TC72 provide a low impedance thermal path
between the die and the PCB, allowing the TC72 to
effectively monitor the temperature of the PCB board.
The thermal path between the ambient air is not as effi-
cient because the plastic IC housing package functions
as a thermal insulator. Thus the ambient air tempera-
ture (assuming that a large temperature gradient exists
between the air and PCB) has only a small effect on the
temperature measured by the TC72.
Note that the exposed metal center pad on the bottom
of the DFN package is connected to the silicon sub-
strate. The center pad should be connected to either
the PCB ground plane or treated as a “No Connect” pin.
The mechanical dimensions of the center pad are given
in Section 6.0, “Packaging Information”, of this
datasheet.
A potential for self-heating errors can exist if the TC72
SPI communication lines are heavily loaded. Typically,
the self-heating error is negligible because of the rela-
tively small current consumption of the TC72. A tem-
perature accuracy error of approximately 0.5°C will
result from self-heating if the SPI communication pins
sink/source the maximum current specified for the
TC72. Thus to maximize the temperature accuracy, the
output loading of the SPI signals should be minimized.
2002 Microchip Technology Inc.
DS21743A-page 13