DS1620 Datasheet, PDF (5/13 Pages) Dallas Semiconductor – Digital Thermometer and Thermostat

DS1620
boundary has been met or exceeded, or as part of a closed loop system it can be used to activate a heating
system and deactivate it when the system temperature returns to tolerance.
The T_COM output goes high when the measured temperature meets or exceeds TH, and will stay high until
the temperature equals or falls below TL. In this way, any amount of hysteresis can be obtained.
THERMOSTAT OUTPUT OPERATION Figure 3
T_HIGH
T_LOW
T_COM
TL
TH
T(°C)
OPERATION AND CONTROL
The DS1620 must have temperature settings resident in the TH and TL registers for thermostatic
operation. A configuration/status register also determines the method of operation that the DS1620 will
use in a particular application and indicates the status of the temperature conversion operation. The
configuration register is defined as follows:
CONFIGURATION/STATUS REGISTER
DONE
THF
TLF
NVB
1
0
CPU
1SHOT
where
DONE = Conversion Done Bit. 1=conversion complete, 0=conversion in progress.
THF = Temperature High Flag. This bit will be set to 1 when the temperature is greater than or equal
to the value of TH. It will remain 1 until reset by writing 0 into this location or by removing power from
the device. This feature provides a method of determining if the DS1620 has ever been subjected to
temperatures above TH while power has been applied.
TLF = Temperature Low Flag. This bit will be set to 1 when the temperature is less than or equal to
the value of TL. It will remain 1 until reset by writing 0 into this location or by removing power from the
device. This feature provides a method of determining if the DS1620 has ever been subjected to
temperatures below TL while power has been applied.
NVB = Nonvolatile Memory Busy Flag. 1=write to an E² memory cell in progress. 0=nonvolatile
memory is not busy. A copy to E² may take up to 10 ms.
CPU = CPU Use Bit. If CPU=0, the CLK/ CONV pin acts as a conversion start control, when RST is
low. If CPU is 1, the DS1620 will be used with a CPU communicating to it over the 3–wire port, and the
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