Rainbow Electronics DS1721 - Manual

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FEATURES
Temperature measurements require no
external components with ±1°C accuracy
Measures temperatures from -55°C to
+125°C; Fahrenheit equivalent is -67°F to
+257°F
Temperature resolution is configurable from 9
to 12 (default) bits (0.5°C to 0.0625°C
resolution)
Maximum conversion time (9-bit resolution)
of 150 ms
Thermostatic settings are user-definable
Data is read/written via a 2-wire serial
interface (open drain I/O lines); 3-bit
addressability
Wide power supply range (2.7V - 5.5V)
Applications include personal computers,
cellular telephones, office equipment, or any
thermally sensitive system
8-pin, 150-mil SOIC package and 8-pin µSOP
package
PIN ASSIGNMENT
PIN DESCRIPTION
SDA - 2-Wire Serial Data Input/Output
SCL - 2-Wire Serial Clock
GND - Ground
T
OUT
- Thermostat Output Signal
A
0
- Chip Address Input
A
1
- Chip Address Input
A
2
- Chip Address Input
V
DD
- Power Supply Voltage (+5V)
DESCRIPTION
The DS1721 2-Wire Digital Thermometer and Thermostat provides 12-bit temperature readings which
indicate the temperature of the device. Thermostatic settings and temperature readings are all
communicated to/from the DS1721 over a simple 2-wire serial interface. No additional components are
required; the device is truly a “temperature-to-digital” converter.
The DS1721 has three address bits that allow a user to multidrop up to eight sensors along the 2-wire bus,
greatly simplifying the bussing of distributed temperature sensing networks.
The thermal alarm output, T
OUT
, is active when the temperature of the device exceeds a user-defined
temperature TH. The output remains active until the temperature is equal to or below the user-defined
temperature TL, allowing for any hysteresis necessary. The active state of T
OUT
is configurable by the
user.
For applications that require faster conversion times, the user can adjust the readout resolution from 12 to
9 bits, effectively reducing the conversion time from 1.2 s (MAX) to 150 ms (MAX). This is particularly
useful in applications where temperature changes large magnitudes very rapidly.
Applications for DS1721 include personal computers/services, cellular telephones, office equipment, or
any microprocessor-based, thermally sensitive system.
DS1721
2-Wire Digital Thermometer
and Thermostat
www.dalsemi.com
1 8
2 7
3 6
4 5
*
DS1721U
8-PIN µ-SOP
V
DD
A
0
A
1
A
2
SDA
SCL
T
OUT
GND
1 8
2 7
3 6
4 5
DS1721S
8-Pin SOIC (150-mil)
SDA
SCL
T
OUT
GND
V
DD
A
0
A
1
A
2