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DS1621S

Part # DS1621S
Description 2-WIRE INTERFACE TEMP.SENSOR8P SO - Rail/Tube
Category IC
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DALLAS SEMICONDUCTOR
Date Code: 0026
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Date Code: 9936
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DALLAS SEMICONDUCTOR
Date Code: 9941
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MAXIM
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Technical Document


DISCLAIMER: The information provided herein is solely for informational purposes. Customers must be aware of the suitability of this product for their application, and consider that variable factors such as Manufacturer, Product Category, Date Codes, Pictures and Descriptions may differ from available inventory.

AVAILABLE
Functional Diagrams
Pin Configurations appear at end of data sheet.
Functional Diagrams continued at end of data sheet.
UCSP is a trademark of Maxim Integrated Products, Inc.
For pricing, delivery, and
ordering information, please contact Maxim Direct
at 1-888-629-4642, or visit Maxim’s website at www.maximintegrated.com.
FEATURES
§ Temperature measurements require no
external components
§ 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 value (2-byte
transfer)
§ Wide power supply range (2.7V to 5.5V)
§ Converts temperature to digital word in less
than 1 second
§ Thermostatic settings are user definable and
nonvolatile
§ Data is read from/written via a 2-wire serial
interface (open drain I/O lines)
§ Applications include thermostatic controls,
industrial systems, consumer products,
thermometers, or any thermal sensitive
system
§ 8-pin DIP or SO package (150mil and
208mil)
PIN ASSIGNMENT
PIN DESCRIPTION
SDA - 2-Wire Serial Data Input/Output
SCL - 2-Wire Serial Clock
GND - Ground
T
OUT
- Thermostat Output Signal
A0 - Chip Address Input
A1 - Chip Address Input
A2 - Chip Address Input
V
DD
- Power Supply Voltage
DESCRIPTION
The DS1621 Digital Thermometer and Thermostat provides 9-bit temperature readings, which indicate
the temperature of the device. 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 drops
below user defined temperature TL, allowing for any hysteresis necessary.
User-defined temperature settings are stored in nonvolatile memory so parts may be programmed prior to
insertion in a system. Temperature settings and temperature readings are all communicated to/from the
DS1621 over a simple 2-wire serial interface.
DS1621
Digital Thermometer and Thermostat
6
3
1
2
4
8
7
5
SD
A
T
OUT
GND
V
DD
A
0
A
1
A
2
DS1621S 8-PIN SO (150mil)
DS1621V 8-PIN SO (208mil)
6
3
1
2
4
8
7
5
SD
A
SCL
T
GND
V
DD
A
0
A
1
A
2
DS1621 8-PIN DIP (300mil)
SCL
090905
DS1621
2 of 16
ORDERING INFORMATION
ORDERING
NUMBER
PACKAGE
MARKING
DESCRIPTION
DS1621 DS1621 DS1621 in 300 mil DIP
DS1621+ DS1621 (See Note) DS1621 in Lead-Free 300 mil DIP
DS1621S DS1621 DS1621 in 150 mil SOIC
DS1621S+ DS1621 (See Note) DS1621 in Lead-Free 150 mil SOIC
DS1621S/T&R DS1621 DS1621 in 150 mil SO, 2500 Piece Tape-and-Reel
DS1621S+T&R DS1621 (See Note) DS1621 in Lead-Free 150 mil SO, 2500 Piece Tape-and-Reel
DS1621V DS1621V DS1621 in 208 mil SOIC
DS1621V+ DS1621V (See Note) DS1621 in Lead-Free 208 mil SOIC
DS1621V/T&R DS1621V DS1621 in 208 mil SO, 2500 Piece Tape-and-Reel
DS1621V+T&R DS1621V (See Note) DS1621 in Lead-Free 208 mil SO, 2500 Piece Tape-and-Reel
Note: A “+” symbol will also be marked on the package near the Pin 1 indicator.
Table 1. DETAILED PIN DESCRIPTION
PIN SYMBOL DESCRIPTION
1 SDA Data input/output pin for 2-wire serial communication port.
2 SCL Clock input/output pin for 2-wire serial communication port.
3 T
OUT
Thermostat output. Active when temperature exceeds TH; will reset when
temperature falls below TL.
4 GND Ground pin.
5 A2 Address input pin.
6 A1 Address input pin.
7 A0 Address input pin.
8 V
DD
Supply voltage input power pin. (2.7V to 5.5V)
OPERATION
Measuring Temperature
A block diagram of the DS1621 is shown in Figure 1.
The DS1621 measures temperature using a bandgap-based temperature sensor. A delta-sigma analog-to-
digital converter (ADC) converts the measured temperature to a digital value that is calibrated in °C; for
°F applications, a lookup table or conversion routine must be used.
The temperature reading is provided in a 9-bit, two’s complement reading by issuing the READ
TEMPERATURE command. Table 2 describes the exact relationship of output data to measured
temperature. The data is transmitted through the 2-wire serial interface, MSB first. The DS1621 can
measure temperature over the range of -55°C to +125°C in 0.5°C increments.
DS1621
3 of 16
Figure 1. DS1621 FUNCTIONAL BLOCK DIAGRAM
STATUS REGISTER &
CONTROL LOGIC
TEMPERATURE SENSOR
HIGH TEMP TRIGGER
,
TH
LOW TEMP TRIGGER
,
TL
DIGITAL COMPARATOR/LOGIC
ADDRESS
AND
I/O CONTROL
SCL
SD
A
A0
A1
A2
T
OUT
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