ds1720 Maxim Integrated Products, Inc., ds1720 Datasheet - Page 4

• Manufacturer Part Number: ds1720
• Description: Ds1720 Econ-digital Thermometer And Thermostat
• Manufacturer: Maxim Integrated Products, Inc.

TEMPERATURE MEASURING CIRCUITRY Figure 2
This calculation is done inside the DS1720 to provide 0.5°C resolution. The temperature reading is
provided in a 9–bit, two’s complement reading by issuing a READ TEMPERATURE command. Table 1
describes the exact relationship of output data to measured temperature. The data is transmitted serially
through the 3–wire serial interface, LSB first. The DS1720 can measure temperature over the range of
–55°C to +125°C in 0.5°C increments. For Fahrenheit usage, a lookup table or conversion factor must be
used.
TEMPERATURE/DATA RELATIONSHIPS Table 1
Since data is transmitted over the 3–wire bus LSB first, temperature data can be written to/read from the
DS1720 as either a 9–bit word (taking
words, with the most significant 7 bits being ignored or set to zero, as illustrated in Table 1. After the
MSB, the DS1720 will output 0s.
Note that temperature is represented in the DS1720 in terms of a ½°C LSB, yielding the following 9–bit
format:
MSB
X
TEMP
+85°C
+25°C
+½°C
-25°C
+0°C
-½°C
X
DIGITAL OUTPUT
X
0 10101010
0 00110010
0 00000001
0 00000000
1 11111111
1 11001110
(Binary)
X
X
X
DIGITAL OUTPUT
X
RST
01CEh
01FFh
low after the 9
0032h
0001h
0000h
(Hex)
00AA
1
T = -25°C
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LSB
1
th
1
(MSB) bit), or as two transfers of 8–bit
0
0
1
1
1
DS1720
0