DS1821S Ver la hoja de datos (PDF) - Dallas Semiconductor -> Maxim Integrated

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DS1821S

Programmable Digital Thermostat and Thermometer

Dallas Semiconductor -> Maxim Integrated 

TEMPERATURE/DATA RELATIONSHIP Table 2

TEMPERATURE

+125°C*

+85°C

+25°C

0°C

-1°C

-25°C

-55°C

DIGITAL OUTPUT

(Binary)

0111 1101

0101 0101

0001 1001

0000 0000

1111 1111

1110 0111

1100 1001

DIGITAL OUTPUT

(Hex)

7Dh

55h

19h

00h

FFh

E7h

C9h

DS1821

HIGH-RESOLUTION TEMPERATURE READINGS

The user can calculate temperature values with higher than 8-bit resolution using the data remaining in

the counter and slope accumulator when the temperature conversion is complete. To do this the user must

first read the temperature from the 8-bit temperature register. This value is called TEMP_READ in the

high-resolution equation (see Eq. 1). The 9-bit counter value must then be obtained by issuing the Read

Counter [A0h] command. This value is the count remaining in the counter at the end of the gate period

and is called COUNT_REMAIN in Eq. 1. Next the Load Counter [41h] command must be issued, which

loads the 9-bit slope accumulator value into the counter register. The slope accumulator value (called

COUNT_PER_C in Eq. 1) can then be read from the counter by again issuing the Read Counter [A0h]

command. The slope accumulator value is called “COUNT_PER_C” because it represents the number of

counts needed for an accurate measurement at a given temperature (i.e., the counts per degree C). The

high-resolution temperature can then be calculated using Eq. 1:

Eq. 1)

TEMPERATURE = TEMP_READ − 0.5 + (COUNT _ PER _ C − COUNT _ REMAIN)

COUNT _ PER _ C

High-resolution temperature readings cannot be used while in continuous conversion mode. Also, the

Read Counter [A0h] and Load Counter [41h] commands must not be used while in continuous conversion

mode.

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