Copyright 1995 by Dallas Semiconductor Corporation.
All Rights Reserved. For important information regarding
patents and other intellectual property rights, please refer to
Dallas Semiconductor data books.
DS1820
1–Wire
TM
Digital Thermometer
DS1820
021497 1/27
FEATURES
•
Unique 1–Wire
TM
interface requires only one port pin
for communication
•
Multidrop capability simplifies distributed temperature
sensing applications
•
Requires no external components
•
Can be powered from data line
•
Zero standby power required
•
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
•
Temperature is read as a 9–bit digital value.
•
Converts temperature to digital word in 200 ms (typ.)
•
User–definable, nonvolatile temperature alarm set-
tings
•
Alarm search command identifies and addresses
devices whose temperature is outside of pro-
grammed limits (temperature alarm condition)
•
Applications include thermostatic controls, industrial
systems, consumer products, thermometers, or any
thermally sensitive system
PIN ASSIGNMENT
3
2
1
DALLAS
DS2434
GND
DQ
VDD
DALLAS
DS1820
3
2
1
DS1820S
16–PIN SSOP
DS1820
PR35 PACKAGE
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
NC
NC
NC
NC
NC
NC
NC
GND
NC
NC
NC
NC
NC
NC
VDD
DQ
BOTTOM VIEW
See Mech. Drawings
Section
See Mech. Drawings
Section
PIN DESCRIPTION
GND
– Ground
DQ
– Data In/Out
V
DD
– Optional V
DD
NC
– No Connect
DESCRIPTION
The DS1820 Digital Thermometer provides 9–bit tem-
perature readings which indicate the temperature of the
device.
Information is sent to/from the DS1820 over a 1–Wire
interface, so that only one wire (and ground) needs to be
connected from a central microprocessor to a DS1820.
Power for reading, writing, and performing temperature
conversions can be derived from the data line itself with
no need for an external power source.
Because each DS1820 contains a unique silicon serial
number, multiple DS1820s can exist on the same
1–Wire bus. This allows for placing temperature sen-
sors in many different places. Applications where this
feature is useful include HVAC environmental controls,
sensing temperatures inside buildings, equipment or
machinery, and in process monitoring and control.
