DS1775 Datasheet, PDF (4/14 Pages) Dallas Semiconductor – SOT23-5 Digital Thermometer and Thermostat

Table 2. Temperature/Data Relationships
S
2⁶
2⁵
2⁴
2³
2²
2¹
2⁰
MSb
(UNIT = °C)
LSb
2^-1
2^-2
2^-3
2^-4
0
0
0
0
DS1775
MSB
LSB
TEMPERATURE
(°C)
+125
+25.0625
+10.125
+0.5
0
-0.5
-10.125
-25.0625
-55
DIGITAL OUTPUT
(BINARY)
0111 1101 0000 0000
0000 1010 0010 0000
0000 1010 0010 0000
0000 0000 1000 0000
0000 0000 0000 0000
1111 1111 1000 0000
1111 0101 1110 0000
1110 0110 1111 0000
1100 1001 0000 0000
DIGITAL OUTPUT
(HEX)
7D00h
1910h
0A20h
0080h
0000h
FF80h
F5E0h
E6F0h
C900h
Thermostat Control
In its comparator operating mode, the DS1775 functions as a thermostat with programmable hysteresis, as
shown in Figure 2. When the DS1775’s temperature meets or exceeds the value stored in the high
temperature trip register (T_OS) a consecutive number of times, as defined by the configuration register, the
output becomes active and stays active until the first time that the temperature falls below the temperature
stored in the low temperature trigger register (T_HYST). In this way, any amount of hysteresis may be
obtained. The DS1775 powers up in the comparator mode with T_OS = +80°C and T_HYST = +75°C and can
be used as a stand-alone thermostat (no 2-wire interface required) with those setpoints.
In the interrupt mode, the O.S. output first becomes active following the programmed number of
consecutive conversions above T_OS. The fault can only be cleared by either setting the DS1775 in a
shutdown mode or by reading any register (temperature, configuration, T_OS, or T_HYST) on the device.
Following a clear, a subsequent fault can only occur if consecutive conversions fall below T_HYST. This
interrupt/clear process is thus cyclical (T_OS, clear, T_HYST, clear, T_OS, clear, T_HYST, clear, etc.). Only the
first of multiple consecutive T_OS violations activates O.S., even if each fault is separated by a clearing
function. The same situation applies to multiple consecutive T_HYST events.
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