DS1629 View Datasheet(PDF) - Dallas Semiconductor -> Maxim Integrated

Part Name

Description

Manufacturer

DS1629

2-Wire Digital Thermometer and Real Time Clock

Dallas Semiconductor -> Maxim Integrated 

DS1629

At the same time, the counter is then preset with a value determined by the slope accumulator circuitry.

This circuitry is needed to compensate for the parabolic behavior of the oscillators over temperature. The

counter is then clocked again until it reaches 0. If the gate period is still not finished, then this process

repeats.

The slope accumulator is used to compensate for the nonlinear behavior of the oscillators over

temperature, yielding a high resolution temperature measurement. This is done by changing the number

of counts necessary for the counter to go through for each incremental degree in temperature. To obtain

the desired resolution, therefore, both the value of the counter and the number of counts per degree C (the

value of the slope accumulator) at a given temperature must be known.

Internally, this calculation is done inside the DS1629 to provide 0.5°C resolution. Table 2 describes the

exact relationship of output data to measured temperature. For Fahrenheit usage, a lookup table or

conversion factor must be used.

Note that temperature is represented in the DS1629 in terms of a 0.5°C LSB, yielding the 9-bit format

illustrated in Table 2. Higher resolutions may be obtained by implementing the algorithm in Application

Note 105 and performing the following calculation. The 8-bit COUNT_REMAIN value can be obtained

via the Read Counter (A8h) command and the COUNT_PER_C value (also 8-bit) is read via the Read

Slope command (A9h).

T = TEMP_READ -0.25 + (COUNT_PER_C_COUNT_REMAIN)

COUNT_PER_C

Temperature/Data Relationships Table 2

S

26

25

24

23

22

MSb

(unit = °C)

2-1

0

0

0

0

0

21

20

MSB

LSb

0

0

LSB

TEMPERATURE

+125°C

+25°C

0.5°C

0°C

-0.5°C

-25°C

-55°C

DIGITAL OUTPUT

(Binary)

01111101 00000000

00011001 00000000

00000000 10000000

00000000 00000000

11111111 10000000

11100111 00000000

11001001 00000000

DIGITAL OUTPUT

(Hex)

7D00h

1900

0080

0000

FF80

E700h

C900h

5 of 22

102299

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