Hardware Reference
In-Depth Information
The TC72 from Microchip is a digital temperature sensor with the SPI interface. The TC72
has a 10-bit resolution; that is, it uses 10 bits to represent the ambient temperature. The pin
assignment and functional block diagram are shown in Figure 10.13.
TC72
V
DD
Internal
diode
temperature
sensor
Manufacturer
ID register
NC
V
DD
1
8
10-bit
sigma-delta
A/D
converter
CE
2
NC
7
CE
SCK
SDO
SDI
TC72
Serial
port
interface
3
6
SCK
SDI
5
GND
4
SDO
Temperature
register
Control
register
GND
Figure 10.13
■
TC72 pin assignment and functional block diagram
The TC72 is capable of reading temperatures from 255°C to 1125°C. The TC72 can be
used either in the
continuous temperature conversion
mode
or the
one-shot conversion mode
.
The continuous conversion mode measures temperature approximately every 150 ms and stores
the data in temperature registers. The TC72 has an internal clock generator that controls the
automatic temperature conversion sequence. In contrast, the one-shot mode performs a single
temperature measurement and returns to the power-saving shutdown mode.
Temperature data is represented by a 10-bit two's complement word with a resolution
of 0.25
°
C per least significant bit. The analog-to-digital converter is scaled from 2128
°
C to
1127
°
C with 0
°
C represented as 0x0000, but the operating range of the TC72 is specified from
255
C. The 10-bit temperature value is stored in two 8-bit registers. Because the
TC72 A/D converter is scaled from 2128
°
C to 1125
°
C and the conversion is represented in
10 bits, the temperature value is equal to the A/C conversion result divided by 4. The lowest
2 bits of the temperature are stored in the highest 2 bits of the lower byte of the temperature
register. The temperature value is represented in the two's complement format. Whenever the
most significant bit of the upper byte of the temperature register is 1, the temperature is
°
C to 1127
°
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