TC773.3MCTTR MICROCHIP [Microchip Technology], TC773.3MCTTR Datasheet - Page 12

• Manufacturer Part Number: TC773.3MCTTR
• Description: Thermal Sensor with SPI Interface
• Manufacturer: MICROCHIP [Microchip Technology]

TC77
5.0
APPLICATION INFORMATION
The TC77 does not require any additional components
in order to measure temperature. However, it is recom-
mended that a decoupling capacitor of 0.1 µF to 1 µF
be provided between the V
and V
(Ground) pins (a
DD
SS
high frequency ceramic capacitor should be used). It is
necessary for the capacitor to be located as close as
possible to the integrated circuit (IC) power pins in
order to provide effective noise protection to the TC77.
The TC77 measures temperature by monitoring the
voltage of a diode located on the IC die. A low-imped-
ance thermal path between the die and the printed cir-
cuit board (PCB) is provided by the IC pins of the TC77.
Therefore, the TC77 effectively monitors the tempera-
ture of the PCB board. The thermal path between the
ambient air is not as efficient because the plastic IC
housing package functions as a thermal insulator.
Thus, the ambient air temperature (assuming that a
large temperature gradient exists between the air and
PCB) has only a small effect on the temperature
measured by the TC77.
A potential for self-heating errors can exist if the TC77
SPI communication lines are heavily loaded. Typically,
the self-heating error is negligible because of the rela-
tively small current consumption of the TC77. 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
TC77. Therefore, to maximize the temperature accu-
racy, the output loading of the SPI signals should be
minimized.
DS20092A-page 12
2002 Microchip Technology Inc.