DS75 Datasheet, PDF (4/13 Pages) Dallas Semiconductor – 2.Wire Thermal Watchdog

DS75
Temperature/Data Relationships Table 2
S
2⁶
2⁵
2⁴
2³
2²
2¹
2⁰ MSB
MSb
(UNIT = °C)
2^–1
2^–2
2^–3
2^–4
0
0
LSb
0
0 LSB
TEMPERATURE/DATA RELATIONSHIPS
Table 2 cont’d
DIGITAL
DIGITAL OUTPUT OUTPUT
TEMP
(Binary)
(Hex)
+125°C
0111 1101 0000 0000
7D00h
+25.0625°C 0001 1001 0001 0000
1910h
+10.125°C 0000 1010 0010 0000
0A20h
+0.5°C 0000 0000 1000 0000
0080h
+0°C
0000 0000 0000 0000
0000h
–0.5°C
1111 1111 1000 0000
FF80h
–10.125°C 1111 0101 1110 0000
E5E0h
–25.0625°C 1110 0110 1111 0000
E6F0h
–55°C
1100 1001 0000 0000
C900h
OPERATION–Thermostat Control
In its comparator operating mode, the DS75 functions as a thermostat with programmable hysteresis, as
shown in Figure 2. When the DS75’s temperature meets or exceeds the value stored in the high tempera-
ture trip register (T_OS ) a consecutive number of times defined by the configuration register, the output
becomes active, and will stay active until the temperature falls below the temperature stored in the low
temperature trigger register (T_HYST ) the first time. In this way, any amount of hysteresis may be obtained.
The DS75 powers up in the comparator mode with T_OS =80°C and T_HYST =75°C, and the device can be
used as a standalone thermostat (no 2–wire interface required) with those setpoints.
In the interrupt mode, the O.S. output will first become active following the programmed number of
consecutive conversions above T_OS . The fault can only be cleared by either setting the DS75 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, . . .). Only the
first of multiple consecutive T_OS violations will activate 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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