DS1775R1-TR 查看數據表（PDF） - Maxim Integrated

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DS1775R1-TR

Digital Thermometer and Thermostat in SOT23

Maxim Integrated 

DS1775

Digital Thermometer and Thermostat in SOT23

Operation

Measuring Temperature

The core of DS1775 functionality is its direct-to-digital

temperature sensor. The DS1775 measures temperature

through the use of an on-chip temperature measurement

technique with an operating range from -55°C to +125°C.

Temperature conversions are initiated upon power-up, and

the most recent result is stored in the thermometer register.

Conversions are performed continuously unless the user

intervenes by altering the configuration register to put the

DS1775 into a shutdown mode. Regardless of the mode

used, the digital temperature can be retrieved from the

temperature register by setting the pointer to that location

(00h, power-up default). The DS1775 power-up default

has the sensor automatically performing 9-bit conversions

continuously. Details on how to change the settings after

power-up are contained in the Programming section.

The resolution of the temperature conversion is configu-

rable (9, 10, 11, or 12 bits), with 9-bit readings the default

state. This equates to a temperature resolution of 0.5°C,

0.25°C, 0.125°C, or 0.0625°C. Following each conver-

sion, thermal data is stored in the thermometer register in

two’s complement format; the information can be retrieved

over the 2-wire interface with the device pointer set to the

temperature register. Table 1 describes the exact relation-

ship of output data to measured temperature. The table

Table 1. Temperature/Data Relationships

assumes the DS1775 is configured for 12-bit resolution; if

the device is configured in a lower resolution mode, those

bits contain zeros. The data is transmitted serially over the

2-wire serial interface, MSb first. The MSb of the tempera-

ture register contains the sign (S) bit, denoting whether the

temperature is positive or negative. For Fahrenheit usage,

a lookup table or conversion routine must be used.

Thermostat Control

In its comparator operating mode, the DS1775 functions

as a thermostat with programmable hysteresis, as shown

in Figure 2. When the DS1775’s temperature meets or

exceeds the value stored in the high temperature trip

register (TOS) a consecutive number of times, as defined

by the configuration register, the output becomes active

and stays active until the first time that the temperature

falls below the temperature stored in the low temperature

trigger register (THYST). In this way, any amount of hys-

teresis may be obtained. The DS1775 powers up in the

comparator mode with TOS = +80°C and THYST = +75°C

and can be used as a stand-alone thermostat (no 2-wire

interface required) with those setpoints.

In the interrupt mode, the O.S. output first becomes active

following the programmed number of consecutive conver-

sions above TOS. The fault can only be cleared by either

setting the DS1775 in a shutdown mode or by reading any

register (temperature, configuration, TOS, or THYST) on

S

26

25

24

23

22

21

20

MSb

(UNIT = °C)

LSb

2-1

2-2

2-3

2-4

0

0

0

0

MSB

LSB

TEMPERATURE

(°C)

+125

+25.0625

+10.125

+0.5

0

-0.5

-10.125

-25.0625

-55

DIGITAL OUTPUT

(BINARY)

0111 1101 0000 0000

0000 1010 0010 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

DIGITAL OUTPUT

(HEX)

7D00h

1910h

0A20h

0080h

0000h

FF80h

F5E0h

E6F0h

C900h

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