19-4886 Rev 8/09 DS1920 Temperature iButton SPECIAL FEATURES COMMON iButton FEATURES Digital Thermometer Measures Temperatures Unique, Factory-Lasered and Tested 64-Bit from -55C to +100C in Typically 0.2s Registration Number (8-Bit Family Code + Zero Standby Power 48-Bit Serial Number + 8-Bit CRC Tester) 0.5C Resolution, Digital Temperature Assures Absolute Traceability Because No Reading is Twos Complement of C Value Two Parts Are Alike Access to Internal Counters Allows Multidrop Controller for MicroLAN Increased Resolution Through Interpolation Digital Identification and Information by Reduces control, Address, Data, and Power Momentary Contact to a Single Data Contact Chip-Based Data Carrier Compactly Stores 8-Bit Device-Generated CRC for Data Information Integrity Data Can Be Accessed While Affixed To 8-Bit Family Code Specifies DS1920 Object Communications Requirements to Reader Economically Communicates to Bus Master Special Command Set Allows User to Skip with a Single Digital Signal at 16.3kbps ROM Section and Perform Temperature Standard 16mm Diameter and 1-Wire Measurements Simultaneously for All Protocol Ensure Compatibility with iButton Devices on the Bus Family 2 Bytes of EEPROM to Be Used Either as Button Shape is Self-Aligning with Cup- Alarm Triggers or User Memory Shaped Probes Alarm Search Directly Indicates Which Durable Stainless Steel Case Engraved with Device Senses Alarming Temperatures Registration Number Withstands Harsh Environments ORDERING INFORMATION Easily Affixed with Self-Stick Adhesive PART PIN-PACKAGE Backing, Latched by Its Flange, or Locked DS1920-F5+ F5 MicroCAN with a Ring Pressed Onto Its Rim +Denotes a lead(Pb)-free/RoHS-compliant package. Presence Detector Acknowledges When F5 MicroCAN Reader First Applies Voltage 5.89 EXAMPLES OF ACCESSORIES 0.51 DS9096P Self-Stick Adhesive Pad DS9101 Multipurpose Clip 16.25 DS9093RA Mounting Lock Ring A0 10 DS9093F Snap-In Fob 17.35 000000FBC52B DS9092 iButton Probe 1-Wire DATA GROUND iButton and 1-Wire are registered trademarks of Maxim Integrated ALL DIMENSIONS ARE SHOWN IN MILLIMETERS. Products, Inc. 1 of 22 DS1920 iButton DESCRIPTION The DS1920 Temperature iButton provides 9-bit temperature readings, which indicate the temperature of the device. Information is sent to/from the DS1920 over a 1-Wire interface. Power for reading, writing, and performing temperature conversions is derived from the data line itself. Because each DS1920 contains a unique silicon serial number, multiple DS1920s can exist on the same 1-Wire bus. This allows for placing temperature sensors 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. OVERVIEW The block diagram of Figure 1 shows the major components of the DS1920. The DS1920 has three main data components: 1) 64-bit lasered ROM, 2) temperature sensor, and 3) nonvolatile temperature alarm triggers TH and TL. The device derives its power from the 1-Wire communication line by storing energy on an internal capacitor during periods of time when the signal line is high and continues to operate off this power source during the low times of the 1-Wire line until it returns high to replenish the parasite (capacitor) supply. Communication to the DS1920 is via a 1-Wire port. With the 1-Wire port, the memory and control functions will not be available before the ROM function protocol has been established. The master must first provide one of five ROM function commands: 1) Read ROM, 2) Match ROM, 3) Search ROM, 4) Skip ROM, or 5) Alarm Search. These commands operate on the 64-bit lasered ROM portion of each device and can single out a specific device if many are present on the 1-Wire line as well as indicate to the bus master how many and what types of devices are present. After a ROM function sequence has been successfully executed, the memory and control functions are accessible and the master may then provide any one of the five memory and control function commands. One control function command instructs the DS1920 to perform a temperature measurement. The result of this measurement will be placed in the DS1920s scratchpad memory, and may be read by issuing a memory function command, which reads the contents of the scratchpad memory. The temperature alarm triggers TH and TL consist of 1 byte of EEPROM each. If the alarm search command is not applied to the DS1920, these registers may be used as general-purpose user memory. Writing TH and TL is done using a memory function command. Read access to these registers is through the scratchpad. All data is read and written least significant bit first. 2 of 22