MAX31722MUA 查看數據表（PDF） - Maxim Integrated

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MAX31722MUA

Digital Thermometers and Thermostats with SPI/3-Wire Interface

Maxim Integrated 

Digital Thermometers and Thermostats

with SPI/3-Wire Interface

Measuring Temperature

The core of the devices’ functionality is its direct-to-digital

temperature sensor. The devices measure temperature

through the use of an on-chip temperature measure-

ment technique with a -55NC to +125NC operating range.

The devices power up in a power-conserving shutdown

mode. After power-up, the devices can be placed in a

continuous conversion mode or in a one-shot conver-

sion mode. In the continuous conversion mode, the

devices continuously compute the temperature and

store the most recent result in the temperature register at

addresses 01h (LSB) and 02h (MSB). As conversions are

performed in the background, reading the temperature

register does not affect the conversion in progress. The

temperature value is not updated until the SPI or 3-wire

interface is inactive. In other words, CE must be inactive

for the temperature register to be updated with the most

recent temperature conversion value. In the one-shot

conversion mode, the devices perform one temperature

conversion and then return to the shutdown mode, storing

temperature in the temperature register. This conversion

mode is ideal for power-sensitive applications. Details on

how to change the setting after power-up are contained

in the Programming section.

The resolution of the temperature conversion is con-

figurable (9, 10, 11, or 12 bits) with 9 bits reading the

default state. This equates to a temperature resolution

of 0.5NC, 0.25NC, 0.125NC, or 0.0625NC. Following each

conversion, thermal data is stored in the temperature

register in two’s complement format. The information

can be retrieved over the SPI or 3-wire interface with the

address set to the temperature register, 01h (LSB) and

then 02h (MSB). Table 1 describes the exact relation-

ship of output data to measured temperature. Table 1

assumes the devices are configured for 12-bit resolution.

If the devices are configured in a lower resolution mode,

those bits contain zeros. The data is transmitted serially

over the digital interface, MSB first for SPI communica-

tion and LSB first for 3-wire communication. The MSB of

the temperature register contains the sign (S) bit, denot-

ing whether the temperature is positive or negative.

S

26

25

24

23

22

21

MSB

(UNITS = NC)

2-1

2-2

2-3

2-4

0

0

0

Figure 5. Temperature, THIGH, and TLOW Register Format

Table 1. 12-Bit Resolution Temperature/Data Relationship

TEMPERATURE

(NC)

+125

+25.0625

+10.125

+0.5

0

-0.5

-10.125

-25.0625

-55

DIGITAL OUTPUT

(BINARY)

0111 1101 0000 0000

0001 1001 0001 0000

0000 1010 0010 0000

0000 0000 1000 0000

0000 0000 0000 0000

1111 1111 1000 0000

1111 0101 1110 0000

1110 0110 1111 0000

1100 1001 0000 0000

20

02h

LSB

0

01h

DIGITAL OUTPUT

(HEX)

7D00

1910

0A20

0080

0000

FF80

F5E0

E6F0

C900

8

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