TC72-2.8MMF datasheet(12/28 Pages) MICROCHIP

12 / 28 page

TC72

DS21743B-page 12

4.1

Temperature Data Format

Temperature data is represented by a 10-bit two’s com-

plement word with a resolution of 0.25°C per bit. The

temperature data is stored in the Temperature registers

in a two’s complement format. The ADC converter is

scaled from -128°C to +127°C, but the operating range

of TC72 is specified from -55°C to +125°C.

EXAMPLE 4-1:

TABLE 4-1:

TC72 TEMPERATURE

OUTPUT DATA

TABLE 4-2:

TEMPERATURE REGISTER

4.2

Power-Up And Power-Down

TC72 is in low-power consumption Shutdown mode at

power-up. The Continuous Temperature Conversion

mode is selected by performing a Write operation to the

Control register, as described in Section 5.0 “Internal

A supply voltage lower than 1.6V (typical) is considered

a power-down state for TC72. If the supply voltage

drops below the 1.6V threshold, the internal registers

are reset to the power-up default state.

4.3

Serial Bus Interface

The serial interface consists of the Chip Enable (CE),

Serial Clock (SCK), Serial Data Input (SDI) and Serial

Data Output (SDO) signals. TC72 operates as a slave

and is compatible with the SPI bus specifications. The

serial interface is designed to be compatible with the

Microchip PIC® family of microcontrollers.

The CE input is used to select TC72 when multiple

devices are connected to the serial clock and data

lines. The CE is active-high, and data is written to or

read from the device, when CE is equal to a logic high

voltage. The SCK input is disabled when CE is low. The

rising edge of the CE line initiates a read or write

operation, while the falling edge of CE completes a

read or write operation.

The

SCK

input

provided

the

external

microcontroller and is used to synchronize the data on

the SDI and SDO lines. The SDI input writes data into

TC72’s Control register, while the SDO outputs the

temperature data from the Temperature register and

the status of Shutdown bit of the Control register.

TC72 has the capability to function with either an

active-high or low SCK input. The SCK inactive state is

detected when the CE signal goes high, while the

polarity of the clock input (CP) determines whether the

data is clocked and shifted on either the rising or falling

edge of the system clock, as shown in Figure 4-2.

Table 4-3 gives the appropriate clock edge used to

transfer data into and out of the registers. Each data bit

is transferred at each clock pulse, and the data bits are

clocked in groups of eight bits, as shown in Figure 4-3.

The address byte is transferred first, followed by the

data. A7, the MSb of the address, determines whether

a read or write operation will occur. If A7 = ‘0’, one or

more read cycles will occur; otherwise, if A7 = ‘1’, one

or more write cycles will occur.

Data can be transferred either in a single byte or a

multi-byte packet, as shown in Figure 4-3. In the 3-byte

packet, the data sequence consists of the MSb

temperature data, LSb temperature data, followed by

the Control register data. The multi-byte read feature is

initiated by writing the highest address of the desired

packet to registers. TC72 will automatically send the

registers, as long as the Chip Enable pin is held active.

Temperature

Binary

MSB / LSB

Hex

+125°C

0111 1101/0000 0000

7D00

+25°C

0001 1001/0000 0000

1900

+0.5°C

0000 0000/1000 0000

0080

+0.25°C

0000 0000/0100 0000

0040

0°C

0000 0000/0000 0000

0000

-0.25°C

1111 1111/1100 0000

FFC0

-25°C

1110 0111/0000 0000

E700

-55°C

1100 1001/0000 0000

C900

Address/

Sign

02H

Temp. MSB

2-1

2-2

000000

01H

Temp. LSB

Temperature

= +41.5°C

MSB Temperature Register

= 00101001b

=25 + 23 + 20

= 32 + 8 + 1 = 41

LSB Temperature Register

= 10000000b = 2-1 = 0.5

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