DS1920-F3 Maxim Integrated Products, DS1920-F3 Datasheet - Page 5

• Manufacturer Part Number: DS1920-F3
• Description: Temperature Ibutton
• Manufacturer: Maxim Integrated Products

The most significant (sign) bit is duplicated into all of the bits in the upper MSB of the 2-byte
temperature register in memory. This “sign-extension” yields the 16-bit temperature readings as shown in
Table 1.
Higher resolutions may be obtained by the following procedure. First, read the temperature, and truncate
the 0.5°C bit (the LSB) from the read value. This value is TEMP_READ. The value left in the counter
may then be read. This value is the count remaining (COUNT_REMAIN) after the gate period has
ceased. The last value needed is the number of counts per degree C (COUNT_PER_C) at that
temperature. The actual temperature may be then be calculated by the user using the following formula:
TEMPERATURE = TEMP_READ - 0.25 +
TEMPERATURE MEASURING CIRCUITRY Figure 3
TEMPERATURE/DATA RELATIONSHIPS Table 1
TEMPERATURE
+100 C
+25 C
+½ C
-25 C
-55 C
+0 C
-½ C
00000000 11001000
00000000 00110010
00000000 00000001
00000000 00000000
11111111 11111111
11111111 11001110
11111111 10010010
DIGITAL OUTPUT
(COUNT_PER
(BINARY)
5 of 22
COUNT_PER_
_C
-
COUNT_REMA
C
IN)
DIGITAL OUTPUT
FFCEH
00C8H
FFFFH
FF92H
0032H
0001H
0000H
(HEX)
SET/CLEAR
LSB
DS1920