Rainbow Electronics DS1720 - Manual (Page 4)

T
HIGH
T
LOW
T COM
TL TH T ( ° C)
DS1720
030598 4/12
DETAILED PIN DESCRIPTION Table 2
PIN SYMBOL DESCRIPTION
1 DQ Data Input/Output pin for 3–wire communication port.
2 CLK/CONV Clock input pin for 3–wire communication port. When the DS1720 is used in a
stand–alone application with no 3–wire port, this pin can be used as a convert pin.
Temperature conversion will begin on the falling edge of CONV.
3 RST Reset input pin for 3–wire communication port.
4 GND Ground pin.
5 T
COM
High/Low Combination Trigger. Goes high when temperature exceeds TH; will
reset to low when temperature falls below TL.
6 T
LOW
Low Temperature Trigger. Goes high when temperature falls below TL.
7 T
HIGH
High Temperature Trigger. Goes high when temperature exceeds TH.
8 V
DD
Supply Voltage. 2.7V – 5.5V input power pin.
OPERATION–THERMOSTAT CONTROLS
Three thermally triggered outputs, T
HIGH
, T
LOW
, and
T
COM
, are provided to allow the DS1720 to be used as a
thermostat, as shown in Figure 3. When the DS1720’s
temperature meets or exceeds the value stored in the
high temperature trip register, the output T
HIGH
becomes active (high) and remains active until the
DS1720’s measured temperature becomes less than
the stored value in the high temperature register, TH.
The T
HIGH
output can be used to indicate that a high
temperature tolerance boundary has been met or
exceeded, or as part of a closed loop system can be
used to activate a cooling system and to deactivate it
when the system temperature returns to tolerance.
The T
LOW
output functions similarly to the T
HIGH
output.
When the DS1720’s measured temperature equals or
falls below the value stored in the low temperature regis-
ter, the T
LOW
output becomes active. T
LOW
remains
active until the DS1720’s temperature becomes greater
than the value stored in the low temperature register,
TL. The T
LOW
output can be used to indicate that a low
temperature tolerance boundary has been met or
exceeded, or as part of a closed loop system, can be
used to activate a heating system and to deactivate it
when the system temperature returns to tolerance.
The T
COM
output goes high when the measured tem-
perature 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