DS1624 Datasheet, PDF (6/16 Pages) Dallas Semiconductor – Digital Thermometer and Memory

TEMPERATURE MEASURING CIRCUITRY Figure 4
SLOPE ACCUMULATOR
DS1624
PRESET
COMPARE
LOW TEMPERATURE
COEFFICIENT OSCILLATOR
COUNTER
PRESET
SET/CLEAR
LSB
INC
=0
TEMPERATURE REGISTER
HIGH TEMPERATURE
COEFFICIENT OSCILLATOR
COUNTER
STOP
=0
Internally, this calculation is performed by the DS1624 to provide 0.03125 °C resolution. The temperature
reading is provided in a 13–bit, two’s complement reading by issuing READ TEMPERATURE
command. Table 2 describes the exact relationship of output data to measured temperature. The data is
transmitted serially through the 2–wire serial interface, MSB first. The DS1624 can measure temperature
over the range of -55°C to +125°C in 0.03125°C increments. For Fahrenheit usage a lookup table or
conversion factor must be used.
TEMPERATURE/DATA RELATIONSHIPS Table 2
TEMP DIGITAL OUTPUT DIGITAL OUTPUT
(Binary)
(Hex)
+125°C
01111101 00000000
7D00h
+25.0625°C 00011001 00010000
1910h
+½°C
00000000 10000000
0080h
+0°C
00000000 00000000
0070h
-½°C
11111111 10000000
FF80h
-25.0625°C 11100110 11110000
E6F0h
-55°C
11001001 00000000
C900h
Since data is transmitted over the 2–wire bus MSB first, temperature data may be written to/read from the
DS1624 as either a single byte (with temperature resolution of 1 °C) or as two bytes, the second byte
containing the value of the 5 least significant bits of the temperature reading as shown in Table 1. Note
that the remaining three bits of this byte are set to all 0’s.
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