Digital Thermometer and
Thermostat
BENEFITS AND FEATURES
Simply Adds Temperature Monitoring and
Control to Any System
o
Measures Temperatures From -55°C to
+125°C in 0.5°C Increments; Fahrenheit
Equivalent is -67°F to +257°F in 0.9°F
Increments
o
Temperature is Read as a 9-Bit Value
o
Converts Temperature to Digital Word in
750ms (max)
o
Thermostatic Settings are User-Definable
and Nonvolatile
Can Be Used in a Wide Variety of
Applications
o
Supply Voltage Range Covers From 2.7V
to 5.5V
o
Data is Read From/Written Via a 3-Wire
Serial Interface (CLK, DQ,
RST
)
Saves Space
o
Requires No External Components
o
8-Pin DIP or SOIC (208-mil) Packages
DS1620
PIN ASSIGNMENT
DQ
CLK/CONV
RST
GND
1
2
3
4
8
7
6
5
V
DD
T
HIGH
T
LOW
T
COM
DS1620S 8-Pin SOIC (208-mil)
DQ
CLK/CONV
RST
GND
1
2
3
4
8
7
6
5
V
DD
T
HIGH
T
LOW
T
COM
DS1620 8-Pin DIP (300-mil)
PIN DESCRIPTION
DQ
CLK/
CONV
GND
T
HIGH
T
LOW
T
COM
V
DD
RST
APPLICATIONS
⋅
⋅
⋅
⋅
Thermostatic Controls
Industrial Systems
Consumer Products
Thermometers
- 3-Wire Input/Output
- 3-Wire Clock Input and
Stand-alone Convert Input
- 3-Wire Reset Input
- Ground
- High Temperature Trigger
- Low Temperature Trigger
- High/Low Combination Trigger
- Power Supply Voltage (3V - 5V)
The DS1620 Digital Thermometer and Thermostat provides 9–bit temperature readings which indicate
the temperature of the device. With three thermal alarm outputs, the DS1620 can also act as a thermostat.
T
HIGH
is driven high if the DS1620’s temperature is greater than or equal to a user–defined temperature
TH. T
LOW
is driven high if the DS1620’s temperature is less than or equal to a user–defined temperature
TL. T
COM
is driven high when the temperature exceeds TH and stays high until the temperature falls
below that of TL.
DESCRIPTION
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19-7539; Rev 3; 3/15
DS1620
User–defined temperature settings are stored in nonvolatile memory, so parts can be programmed prior to
insertion in a system, as well as used in standalone applications without a CPU. Temperature settings and
temperature readings are all communicated to/from the DS1620 over a simple 3–wire interface.
ORDERING INFORMATION
PART
DS1620
DS1620+
DS1620S
DS1620S+
DS1620S/T&R
DS1620S+T&R
DESCRIPTION
8-Pin DIP (300 mil)
Lead-Free 8-Pin DIP (300 mil)
8-Pin SOIC (208 mil)
Lead-Free 8-Pin SOIC (208 mil)
8-Pin SOIC (208 mil), 2000-Piece Tape-and-Reel
Lead-Free 8-Pin SOIC (208 mil), 2000-Piece
Tape-and-Reel
Note: A “+” symbol will also be marked on the package near the Pin 1 indicator
PACKAGE MARKING
DS1620
DS1620 (See Note)
DS1620
DS1620 (See Note)
DS1620
DS1620 (See Note)
DETAILED PIN DESCRIPTION
Table 1
PIN
1
2
3
4
5
6
7
8
SYMBOL
DQ
CLK/
CONV
GND
T
COM
T
LOW
T
HIGH
V
DD
RST
DESCRIPTION
Data Input/Output pin
for 3-wire communication port.
Clock input pin
for 3-wire communication port. When the DS1620 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
.
Reset input pin
for 3-wire communication port.
Ground pin.
High/Low Combination Trigger.
Goes high when temperature exceeds TH;
will reset to low when temperature falls below TL.
Low Temperature Trigger.
Goes high when temperature falls below TL.
High Temperature Trigger.
Goes high when temperature exceeds TH.
Supply Voltage.
2.7V – 5.5V input power pin.
Table 2. DS1620 REGISTER SUMMARY
REGISTER NAME
(USER ACCESS)
Temperature
(Read Only)
T
H
(Read/Write)
T
L
(Read/Write)
SIZE
9 Bits
9 Bits
9 Bits
MEMORY
TYPE
SRAM
EEPROM
EEPROM
REGISTER CONTENTS
AND POWER-UP/POR STATE
Measured Temperature (Two’s Complement)
Power-Up/POR State: -60ºC (1 1000 1000)
Upper Alarm Trip Point (Two’s Complement)
Power-Up/POR State: User-Defined.
Initial State from Factory: +15°C (0 0001 1110)
Lower Alarm Trip Point (Two’s Complement)
Power-Up/POR State: User-Defined.
Initial State from Factory: +10°C (0 0001 0100)
OPERATION-MEASURING TEMPERATURE
A block diagram of the DS1620 is shown in Figure 1.
..
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DS1620
DS1620 FUNCTIONAL BLOCK DIAGRAM
Figure 1
The DS1620 measures temperature using a bandgap-based temperature sensor. The temperature reading
is provided in a 9–bit, two’s complement reading by issuing a READ TEMPERATURE command. The
data is transmitted serially through the 3–wire serial interface, LSB first. The DS1620 can measure
temperature over the range of -55°C to +125°C in 0.5°C increments. For Fahrenheit usage, a lookup table
or conversion factor must be used.
Since data is transmitted over the 3–wire bus LSB first, temperature data can be written to/read from the
DS1620 as either a 9–bit word (taking
RST
low after the 9
th
(MSB) bit), or as two transfers of 8–bit
words, with the most significant 7 bits being ignored or set to 0, as illustrated in Table 3. After the MSB,
the DS1620 will output 0s.
Note that temperature is represented in the DS1620 in terms of a ½°C LSB, yielding the 9–bit format
shown in Figure 2.
TEMPERATURE, TH, and TL REGISTER FORMAT
Figure 2
MSB
X
X
X
X
X
X
X
1
T = -25°C
LSB
1
1
0
0
1
1
1
0
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DS1620
Table 3 describes the exact relationship of output data to measured temperature.
.
TEMPERATURE/DATA RELATIONSHIPS
Table 3
TEMP
+125˚C
+25˚C
+½˚C
+0˚C
-½˚C
-25˚C
-55˚C
DIGITAL OUTPUT
(Binary)
0 11111010
0 00110010
0 00000001
0 00000000
1 11111111
1 11001110
1 10010010
DIGITAL OUTPUT
(Hex)
00FA
0032h
0001h
0000h
01FFh
01CEh
0192h
Higher resolutions may be obtained by reading the temperature, and truncating 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 by
issuing a READ COUNTER command. This value is the count remaining (COUNT_REMAIN) after the
gate period has ceased. By loading the value of the slope accumulator into the count register (using the
READ SLOPE command), this value may then be read, yielding 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:
TEMPERATURE=TEMP_READ-0.25 +
(COUNT_PER_C - COUNT_REMAIN)
COUNT_PER_C
Three thermally triggered outputs, T
HIGH
, T
LOW
, and T
COM
, are provided to allow the DS1620 to be used
as a thermostat, as shown in Figure 3. When the DS1620’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
DS1620’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 it can be used as part of a closed loop system to activate a cooling system and deactivate it
when the system temperature returns to tolerance.
The T
LOW
output functions similarly to the T
HIGH
output. When the DS1620’s measured temperature
equals or falls below the value stored in the low temperature register, the T
LOW
output becomes active.
T
LOW
remains active until the DS1620’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 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.
OPERATION–THERMOSTAT CONTROLS
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THERMOSTAT OUTPUT OPERATION
Figure 3
T
HIGH
DS1620
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. The power-up/POR
state is a 1.
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. The power-up/POR state is a 0.
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. The power-up/POR state is a 0.
NVB = Nonvolatile Memory Busy Flag. 1=write to an E
2
memory cell in progress. 0=nonvolatile
memory is not busy. A copy to E
2
may take up to 10 ms. The power-up/POR state is a 0.
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
operation of the CLK/
CONV
pin is as a normal clock in concert with DQ and
RST
. This bit is stored in
nonvolatile E
2
memory, capable of at least 50,000 writes. The DS1620 is shipped with CPU=0.
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