DS1621 Digital Thermometer and BENEFITS AND FEATURES PIN ASSIGNMENT Simply Adds Temperature Monitoring and 8 SDA 1 V DD Control to Any System 2 7 o Measures Temperatures From -55C to SCL A 0 +125C in 0.5C Increments. Fahrenheit 6 T 3 A OUT 1 Equivalent is -67F to 257F in 0.9F 4 5 Increments GND A 2 o Temperature is Read as a 9-Bit Value (2- Byte Transfer) DS1621S 8-PIN SO (150mil) o Converts Temperature to Digital Word in DS1621V 8-PIN SO (208mil) Less than 1s o Thermostatic Settings are User Definable And Nonvolatile 1 8 V DD SDA Can Be Used in a Wide Variety of 7 Applications 2 A 0 SCL o Power Supply Range (2.7V to 5.5V) 3 6 A 1 T o Data is Read From/Written Via a 2-Wire OUT Serial Interface (Open Drain I/O Lines) 5 4 A 2 GND Saves Space DS1621 8-PIN DIP (300mil) o Temperature Measurements Require No External Components o 8-pin DIP or SO package (208-mil) Packages APPLICATIONS PIN DESCRIPTION SDA - 2-Wire Serial Data Input/Output Thermostatic Controls SCL - 2-Wire Serial Clock Industrial Systems GND - Ground Consumer Products T - Thermostat Output Signal OUT Thermometers A0 - Chip Address Input A1 - Chip Address Input A2 - Chip Address Input V - Power Supply Voltage DD DESCRIPTION The DS1621 Digital Thermometer and Thermostat provides 9-bit temperature readings, which indicate the temperature of the device. The thermal alarm output, T , is active when the temperature of the OUT 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. 1 of 16 19-7540 Rev 4 3/15 DS1621 ORDERING INFORMATION ORDERING PACKAGE DESCRIPTION NUMBER MARKING 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 Thermostat output. Active when temperature exceeds TH will reset when OUT 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 Supply voltage input power pin. (2.7V to 5.5V) DD 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, twos 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 -55C to +125C in 0.5C increments. 2 of 16