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PRELIMINARY
DS1821
Programmable Digital Thermostat and
Thermometer
www.dalsemi.com
FEATURES
Requires no external components
Unique 1-Wire
廬
interface requires only one
port pin for communication
Operates over a -55擄C to +125擄C (67擄F to
+257擄F) temperature range
Functions as a standalone thermostat with
user-definable trip-points
Provides 8-bit (1擄C resolution) centigrade
temperature measurements
Accuracy is
鹵1擄C
over 0擄C to +85擄C range
Converts temperature to a digital word in 1
second (max)
Available in 3-pin PR35 and 8-pin SOIC
packages
Applications include thermostatic controls,
industrial systems, consumer products,
thermometers, or any thermally sensitive
system
PIN ASSIGNMENT
DQ
DALLAS
1
8
V
DD
NC
NC
NC
DS1821S
DS1821
1 2 3
GND
NC
NC
2
3
4
7
6
5
8-pin 208-mil SOIC
(DS1821S)
(BOTTOM VIEW)
PR35
(DS1821)
PIN DESCRIPTION
GND
DQ
V
DD
NC
- Ground
- Data In/Out and Thermostat Output
- Power Supply Voltage
- No Connect
DESCRIPTION
The DS1821 can function as a standalone thermostat with user-programmable trip-points or as 8-bit
temperature sensor with a 1-wire digital interface. The thermostat trip-points are stored in nonvolatile
memory, so DS1821 units can be programmed prior to system insertion for true standalone operation.
The DS1821 has an operating temperature range of 鈥?5擄C to +125擄C and is accurate to
鹵1擄C
over a range
of 0擄C to +85擄C. Communication with the DS1821 is accomplished through the open-drain DQ pin; this
pin also serves as the thermostat output.
1 of 17
GND
DQ
V
DD
1 2
3
040601