DS1920 Temperature iButton COMMON iButton FEATURES Digital T
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19-4886; 8/09
DS1920 Temperature iButton
COMMON iButton FEATURES
Digital Thermometer Measures Temperatures from -55°C +100°C Typically 0.2s Zero Standby Power 0.5°C Resolution, Digital Temperature Reading Two's Complement Value Access Internal Counters Allows Increased Resolution Through Interpolation Reduces control, Address, Data, Power Single Data Contact 8-Bit Device-Generated Data Integrity 8-Bit Family Code Specifies DS1920 Communications Requirements Reader Special Command Allows User Skip Section Perform Temperature Measurements Simultaneously Devices Bytes EEPROM Used Either Alarm Triggers User Memory Alarm Search Directly Indicates Which Device Senses Alarming Temperatures PIN-PACKAGE MicroCAN
ORDERING INFORMATION
PART DS1920-F5+
+Denotes lead(Pb)-free/RoHS-compliant package.
MicroCAN
5.89 0.51
Unique, Factory-Lasered Tested 64-Bit Registration Number (8-Bit Family Code 48-Bit Serial Number 8-Bit Tester) Assures Absolute Traceability Because Parts Alike Multidrop Controller MicroLAN Digital Identification Information Momentary Contact Chip-Based Data Carrier Compactly Stores Information Data Accessed While Affixed Object Economically Communicates Master with Single Digital Signal 16.3kbps Standard 16mm Diameter 1-Wire Protocol Ensure Compatibility with iButton Family Button Shape Self-Aligning with CupShaped Probes Durable Stainless Steel Case Engraved with Registration Number Withstands Harsh Environments Easily Affixed with Self-Stick Adhesive Backing, Latched Flange, Locked with Ring Pressed Onto Presence Detector Acknowledges When Reader First Applies Voltage Self-Stick Adhesive Multipurpose Clip Mounting Lock Ring Snap-In iButton Probe
EXAMPLES ACCESSORIES
16.25
000000FBC52B
1-Wire
17.35
DS9096P DS9101 DS9093RA DS9093F DS9092
DATA
GROUND
iButton 1-Wire registered trademarks Maxim Integrated Products, Inc.
DIMENSIONS SHOWN MILLIMETERS.
DS1920
iButton DESCRIPTION
DS1920 Temperature iButton provides 9-bit temperature readings, which indicate temperature device. Information sent to/from DS1920 over 1-Wire interface. Power reading, writing, performing temperature conversions derived from data line itself. Because each DS1920 contains unique silicon serial number, multiple DS1920s exist same 1-Wire bus. This allows placing temperature sensors many different places. Applications where this feature useful include HVAC environmental controls, sensing temperatures inside buildings, equipment machinery, process monitoring control.
OVERVIEW
block diagram Figure shows major components DS1920. DS1920 three main data components: 64-bit lasered ROM, temperature sensor, nonvolatile temperature alarm triggers device derives power from 1-Wire communication line storing energy internal capacitor during periods time when signal line high continues operate this power source during times 1-Wire line until returns high replenish parasite (capacitor) supply. Communication DS1920 1-Wire port. With 1-Wire port, memory control functions will available before function protocol been established. master must first provide five function commands: Read ROM, Match ROM, Search ROM, Skip ROM, Alarm Search. These commands operate 64-bit lasered portion each device single specific device many present 1-Wire line well indicate master many what types devices present. After function sequence been successfully executed, memory control functions accessible master then provide five memory control function commands. control function command instructs DS1920 perform temperature measurement. result this measurement will placed DS1920's scratchpad memory, read issuing memory function command, which reads contents scratchpad memory. temperature alarm triggers consist byte EEPROM each. alarm search command applied DS1920, these registers used general-purpose user memory. Writing done using memory function command. Read access these registers through scratchpad. data read written least significant first.
DS1920
DS1920 BLOCK DIAGRAM Figure
PARASITE POWER
block diagram (Figure shows parasite-powered circuitry. This circuitry "steals" power whenever data contact high. Data will provide sufficient power long specified timing voltage requirements (see 1-Wire System section). advantage parasite power that local power source needed remote sensing temperature. order DS1920 able perform accurate temperature conversions, sufficient power must provided over data line when temperature conversion taking place. DS1920 requires current during conversion 1mA, therefore, data line will have sufficient drive pullup resistor. This problem particularly acute several DS1920s same data line attempting convert simultaneously. assure that DS1920 sufficient supply current provide strong pullup data line whenever temperature conversion copying EEPROM taking place. This accomplished using MOSFET connect data line directly power supply shown Figure data line must switched over strong pullup within maximum after issuing command that involves copying EEPROM initiates temperature conversion.
DS1920
STRONG PULLUP SUPPLYING DS1920 DURING TEMPERATURE CONVERSION Figure
OPERATION-MEASURING TEMPERATURE
DS1920 measures temperatures through on-board proprietary temperature measurement technique. block diagram temperature measurement circuitry shown Figure DS1920 measures temperature counting number clock cycles that oscillator with temperature coefficient goes through during gate period determined high temperature coefficient oscillator. counter preset with base count that corresponds -55°C. counter reaches before gate period over, temperature register, which also preset -55°C value, incremented, indicating that temperature higher than -55°C. same time, counter then preset with value determined slope accumulator circuitry. counter then clocked again until reaches gate period still finished, then this process repeats. slope accumulator compensates nonlinear behavior oscillators over temperature, yielding high-resolution temperature measurement. This done changing number counts necessary counter through each incremental degree temperature. obtain desired resolution, therefore, both value counter number counts degree (the value slope accumulator) given temperature must known. Internally, this calculation done inside DS1920 provide 0.5°C resolution. temperature reading provided 16-bit, sign-extended two's complement reading. Table describes exact relationship output data measured temperature. data transmitted serially over 1-Wire interface. DS1920 measure temperature over range -55°C +100°C 0.5°C increments. Fahrenheit usage, lookup table conversion factor must used. Note that temperature represented DS1920 terms 1/2°C LSB, yielding following 9-bit format: -25°C
DS1920
most significant (sign) duplicated into bits upper 2-byte temperature register memory. This "sign-extension" yields 16-bit temperature readings shown Table Higher resolutions obtained following procedure. First, read temperature, truncate 0.5°C (the LSB) from read value. This value TEMP_READ. value left counter then read. This value count remaining (COUNT_REMAIN) after gate period ceased. last value needed number counts degree (COUNT_PER_C) that temperature. actual temperature then calculated user using following formula: TEMPERATURE TEMP_READ 0.25
(COUNT_PER_C COUNT_REMAIN) COUNT_PER_C
TEMPERATURE MEASURING CIRCUITRY Figure
SET/CLEAR
TEMPERATURE/DATA RELATIONSHIPS Table
TEMPERATURE DIGITAL OUTPUT (BINARY) DIGITAL OUTPUT (HEX)
+100C +25C -25C -55C
00000000 11001000 00000000 00110010 00000000 00000001 00000000 00000000 11111111 11111111 11111111 11001110 11111111 10010010
00C8h 0032h 0001h 0000h FFFFh FFCEh FF92h
DS1920
OPERATION-ALARM SIGNALING
After DS1920 performed temperature conversion, temperature value compared trigger values stored Since these registers bits only, 0.5°C ignored comparison. most significant directly corresponds sign 16-bit temperature register. result temperature measurement higher than lower than alarm flag inside device set. This flag updated with every temperature measurement. long alarm flag set, DS1920 will respond alarm search command. This allows many DS1920s connected parallel doing simultaneous temperature measurements. somewhere temperature exceeds limits, alarming device(s) identified read immediately without having read nonalarming devices.
64-BIT LASERED
Each DS1920 contains unique code that bits long. first bits 1-Wire family code (DS1920 code 10h). next bits unique serial number. last bits first bits. (See Figure 64-bit Function Control section allow DS1920 operate 1-Wire device follow 1-Wire protocol detailed 1-Wire System section. memory control functions DS1920 accessible until function protocol been satisfied. This protocol described function protocol flowchart (Figure 1-Wire master must first provide five function commands: Read ROM, Match ROM, Search ROM, Skip ROM, Alarm Search. After function sequence been successfully executed, functions specific DS1920 accessible master then provide five memory control function commands.
GENERATION
DS1920 8-bit stored most significant byte 64-bit ROM. master compute value from first bits 64-bit compare value stored within DS1920 determine data been received error-free master. equivalent polynomial function this DS1920 also generates 8-bit value using same polynomial function shown above provides this value master validate transfer data bytes. each case where used data transfer validation, master must calculate value using polynomial function given above compare calculated value either 8-bit value stored 64-bit portion DS1920 (for reads) 8-bit value computed within DS1920 (which read byte when scratchpad read). comparison values decision continue with operation determined entirely master. There circuitry inside DS1920 that prevents command sequence from proceeding stored calculated DS1920 does match value generated master. 1-Wire generated using polynomial generator consisting shift register gates shown Figure Additional information about Dallas 1-Wire Cyclic Redundancy Check available Book iButton Standards. shift register bits first initialized section, starting with least significant family code, time shifted After family code been entered, then serial number entered. After 48th serial number been entered, shift register contains value. Shifting bits should return shift register
DS1920
64-BIT LASERED Figure
8-BIT CODE 48-BIT SERIAL NUMBER 8-BIT FAMILY CODE (10H)
FUNCTIONS FLOWCHART Figure
DS1920
1-Wire CODE Figure
MEMORY
DS1920's memory organized shown Figure memory consists scratchpad bytes EEPROM that store high temperature triggers scratchpad helps insure data integrity when communicating over 1-Wire bus. Data first written scratchpad where read back. After data been verified, copy scratchpad command will transfer data EEPROM. This process ensures data integrity when modifying memory. scratchpad organized bytes memory. first bytes contain measured temperature information. bytes volatile copies refreshed with every poweron reset. next bytes used; upon reading back, however, they will appear logic bytes count registers, which used obtaining higher temperature resolution (see Operation-Measuring Temperature section). There byte that read with Read Scratchpad command. This byte cyclic redundancy check (CRC) over previous bytes. This implemented described Generation section.
DS1920 MEMORY Figure
SCRATCHPAD TEMPERATURE TEMPERATURE TH/USER BYTE TL/USER BYTE RESERVED RESERVED COUNT REMAIN COUNT BYTE TH/USER BYTE TL/USER BYTE EEPROM
DS1920
1-Wire SYSTEM
1-Wire system that single master more slaves. DS1920 behaves slave. discussion this system broken down into three topics: hardware configuration, transaction sequence, 1-Wire signaling (signal types timing).
HARDWARE CONFIGURATION
1-Wire only single line definition; important that each device able drive appropriate time. facilitate this, each device attached 1-Wire must have opendrain 3-state outputs. 1-Wire port DS1920 (data contact) open drain with internal circuit equivalent that shown Figure multidrop consists 1-Wire with multiple slaves attached. 1-Wire requires pullup resistor approximately idle state 1-Wire high. reason transaction needs suspended, MUST left idle state transaction resume. this does occur left more than 120s, more devices will reset.
HARDWARE CONFIGURATION Figure
TRANSACTION SEQUENCE
protocol accessing DS1920 1-Wire port follows: Initialization Function Command Memory/Control Function Command Transaction/Data
INITIALIZATION
transactions 1-Wire begin with initialization sequence. initialization sequence consists reset pulse transmitted master followed presence pulse(s) transmitted slave(s). presence pulse lets master know that DS1920 ready operate. more details, 1-Wire Signaling section.
DS1920
FUNCTION COMMANDS
Once master detected presence pulse, issue five function commands. function commands eight bits long. list these commands follows (see flowchart Figure
Read [33h]
This command allows master read DS1920's 8-bit family code, unique 48-bit serial number, 8-bit CRC. This command only used there single DS1920 bus. more than slave present bus, data collision will occur when slaves transmit same time (open drain will produce wired-AND result).
Match [55h]
match command, followed 64-bit sequence, allows master address specific DS1920 multidrop bus. Only DS1920 that exactly matches 64-bit sequence will respond subsequent memory function command. slaves that match 64-bit sequence will wait reset pulse. This command used with single multiple devices bus.
Skip [CCh]
This command save time single drop system allowing master access memory functions without providing 64-bit code. more than slave present read command issued following Skip command, data collision will occur multiple slaves transmit simultaneously (open-drain pulldowns will produce wired-AND result). Skip command useful address DS1920s temperature conversion. Since DS1920 uses special command set, other device types will respond these commands.
Search [F0h]
When system initially brought master might know number devices 1-Wire their 64-bit codes. search command allows master process elimination identify 64-bit codes slave devices bus. search process repetition simple, three-step routine: read bit, read complement bit, then write desired value that bit. master performs this simple, three-step routine each ROM. After complete pass, master knows contents device. remaining number devices their codes identified additional passes. Refer Chapter Book iButton Standards comprehensive discussion Search, including actual example.
Alarm Search [ECh]
flowchart this command identical Search command; however, DS1920 will respond this command only alarm condition been encountered last temperature measurement. alarm condition defined temperature higher than lower than alarm condition remains long DS1920 powered until another temperature measurement reveals nonalarming value. alarming, trigger values stored EEPROM taken into account. alarm condition exists settings changed, another temperature conversion should done validate alarm conditions.
DS1920
MEMORY CONTROL FUNCTION COMMANDS
following command protocols summarized Table flowchart Figure
Write Scratchpad [4Eh]
This command writes scratchpad DS1920, starting address next bytes written will saved scratchpad memory, address locations Writing terminated point issuing reset. However, reset occurs before both bytes have been completely sent, contents these bytes will indeterminate. Bytes read written; other bytes read only.
Read Scratchpad [BEh]
This command reads complete scratchpad. After last byte scratchpad read, master will receive 8-bit scratchpad bytes. locations read, master issue reset terminate reading time.
Copy Scratchpad [48h]
This command copies from scratchpad into EEPROM DS1920, storing temperature trigger bytes nonvolatile memory. master enable strong pullup least immediately after issuing this command.
Convert Temperature [44h]
This command begins temperature conversion. further data required. master enable strong pullup 0.75 seconds immediately after issuing this command.
Recall [B8h]
This command recalls temperature trigger values stored EEPROM scratchpad. This recall operation happens automatically upon power-up DS1920 well, valid data available scratchpad soon device power applied.
DS1920
MEMORY CONTROL FUNCTIONS FLOWCHART Figure
DS1920
MEMORY CONTROL FUNCTIONS FLOWCHART (continued) Figure
FROM FIGURE FIRST PART FIGURE THIRD PART
DS1920
MEMORY CONTROL FUNCTIONS FLOWCHART (continued) Figure
1-Wire SIGNALING
DS1920 requires strict protocols ensure data integrity. protocol consists five types signaling line: Reset Sequence with Reset Pulse Presence Pulse, Write Write Read Data Strong Pullup. these signals except Presence Pulse initiated master. initialization sequence required begin communication with DS1920 shown Figure Reset Pulse followed Presence Pulse indicates DS1920 ready accept command. master transmits (Tx) Reset Pulse (tRSTL, minimum 480s). master then releases line goes into receive mode (Rx). 1-Wire pulled high state pullup resistor. After detecting rising edge 1-Wire line, DS1920 waits (tPDH, 15-60s) then transmits Presence Pulse (tPDL, 60-240s).
DS1920
READ/WRITE TIME SLOTS
definitions write read time slots illustrated Figure time slots initiated master driving data line low. falling edge data line synchronizes DS1920 master triggering delay circuit DS1920. During write time slots, delay circuit determines when DS1920 will sample data line. read data time slot, transmitted, delay circuit determines long DS1920 will hold data line overriding generated master. data DS1920 will leave read data time slot unchanged.
STRONG PULLUP
provide energy temperature conversion copying data from scratchpad EEPROM, low-impedance pullup 1-Wire required just after corresponding command been sent master. During temperature conversion copying scratchpad, master controls transition from state where data line idling high pullup resistor state where data line actively driven providing minimum current each DS1920 doing temperature conversion. This impedance pullup should active 0.75 seconds temperature conversion least 10ms copying scratchpad. After that, data line returns idle high state controlled pullup resistor. low-impedance pullup does affect other devices 1-Wire bus. Therefore, possible multidrop other 1-Wire devices with DS1920.
INITIALIZATION PROCEDURE "RESET PRESENCE PULSES" Figure
RESISTOR MASTER DS1920
480s tRSTL 480s tRSTH (includes recovery time) tPDH tPDL 240s
order mask interrupt signaling other devices 1-Wire bus, tRSTL should
always less than 960s.
DS1920
DS1920 MEMORY CONTROL FUNCTION COMMANDS Table
INSTRUCTION 1-Wire DESCRIPTION PROTOCOL AFTER ISSUING PROTOCOL TEMPERATURE CONVERSION COMMANDS Initiates temperature strong pullup conversion MEMORY COMMANDS Reads bytes from scratchpad <read data reads byte. bytes> Writes bytes into scratchpad <write data into addresses bytes addr. temperature triggers). addr. Copies Scratchpad into nonvolatile memory strong pullup (addresses only). Recalls values stored nonvolatile memory into idle scratchpad (temperature triggers). NOTES
Convert Temperature Read Scratchpad Write Scratchpad
Copy Scratchpad
Recall
NOTES:
Temperature conversion takes 0.75 seconds. After receiving Convert Temperature command, data line DS1920 must held high least 0.75 seconds provide power during conversion process. such, other activity take place 1-Wire least this period after Convert Temperature command been issued. After receiving Copy Scratchpad command, data line DS1920 must held high least 10ms provide power during copy process. such, other activity take place 1-Wire least this period after Copy Scratchpad command been issued.
READ/WRITE TIMING DIAGRAM Figure Write-1 Time Slot
RESISTOR MASTER
tSLOT 120s tLOW1 tREC
DS1920
READ/WRITE TIMING DIAGRAM (continued) Figure Write-0 Time Slot
tLOW0 tSLOT 120s tREC
Read-Data Time Slot
RESISTOR MASTER DS1920
tSLOT 120s tLOWR tRELEASE tREC tRDV
DS1920
MEMORY FUNCTION EXAMPLE Table
Example: Master initiates temperature conversion, then reads temperature. MASTER MODE DATA (LSB FIRST) Reset Presence <64-bit code> <DATA LINE HIGH> Reset Presence <64-bit code> COMMENTS Reset pulse(480-960s) Presence pulse Issue "Match ROM" command Issue address DS1920 Issue "Convert Temperature" command Data line held high least 0.75 seconds master allow conversion complete. Reset pulse Presence pulse Issue "Match ROM" command Issue address DS1920 Issue "Read Scratchpad" command. Read entire scratchpad plus CRC; master recalculates eight data bytes received from scratchpad, compares calculated read. they match, master continues; not, this read operation repeated. Reset pulse Presence pulse, done
data bytes>
Reset Presence
DS1920
ABSOLUTE MAXIMUM RATINGS
Voltage Relative Ground Operating Temperature Storage Temperature -0.5V +7.0V -55°C +100°C -55°C +100°C
This stress rating only functional operation device these other conditions above those indicated operation sections this specification implied. Exposure absolute maximum rating conditions extended periods time affect device reliability.
ELECTRICAL CONDITIONS
-55°C +100°C.) PARAMETER SYMBOL CONDITIONS Functions +1/2°C Accurate Temperature Conversions UNITS NOTES
Pullup Voltage
VPUP
-0.3
Logic Logic
ELECTRICAL CHARACTERISTICS
(VPUP 4.3V 6.0V, -55°C +100°C.) PARAMETER SYMBOL CONDITIONS Thermometer -55C tERR Error +100 Active Current Input Load Current Output Logic UNITS NOTES
TYPICAL CURVE 1000 1500
CAPACITANCE
+25°C) PARAMETER (1-Wire) SYMBOL CIN/OUT UNITS NOTES
ELECTRICAL CHARACTERISTICS: TEMPERATURE CONVERSION COPY SCRATCHPAD
(VPUP 4.3V 6.0V, -55°C +100°C.) PARAMETER SYMBOL Temperature Conversion tCONV Copy Scratchpad tCOPY 0.75 UNITS seconds NOTES
DS1920
ELECTRICAL CHARACTERISTICS: 1-Wire INTERFACE
(VPUP 2.8V 6.0V, -55°C +100°C.) PARAMETER SYMBOL Time Slot tSLOT Write Time tLOW1 Write Time tLOW0 Read Data Valid tRDV Release Time tRELEASE Read Data Setup Recovery Time tREC Reset Time High tRSTH Reset Time tRSTL Presence Detect High tPDHIGH Presence Detect tPDLOW UNITS NOTES
exactly
4800
NOTES:
Temperature conversion will work with ±2°C accuracy down VPUP 3.4V. voltages referenced ground. specified with low-impedance pullup 5.0V. Active current refers temperature conversion. Writing EEPROM consumes approximately 200A. tRSTL 4800s. With longer times, result temperature conversion lost. reset time should restricted maximum 960s, allow interrupt signaling, otherwise could mask conceal interrupt pulses. Read data setup time refers time host must pull 1-Wire read bit. Data guaranteed valid within this falling edge will remain valid minimum (15s total from falling edge 1-Wire bus). Capacitance data contact could 800pF when power first applied. resistor used pull data line VCC, after power been applied, parasite capacitance will affect normal communications. Under certain low-voltage conditions, VILMAX have reduced much 0.5V always guarantee presence pulse. Typical Performance Curve specification limits outside +70°C range. Thermometer error reflects sensor accuracy tested during calibration.
DS1920
TYPICAL PERFORMANCE CURVE
DS1920 TEMPERATURE iButton
TRUE TEMPERATURE
ERROR READING TRUE TEMPERATURE WHEN COLD, TRUE TEMPERATURE TYPICALLY COLDER THAN TEMPERATURE READING.
PACKAGE INFORMATION
latest package outline information land patterns, www.maxim-ic.com/packages.
PACKAGE TYPE MicroCAN
PACKAGE CODE IB+5NS
DOCUMENT 21-0266
DS1920
REVISION HISTORY
REVISION DATE 082906 110806 040108 DESCRIPTION Common iButton Features, reworded statement. Extended temperature conversion time from 0.5s 0.75s maximum. Removed MicroCAN drawing ordering information; added lead-free DS1920-F5+ removed leaded package from Ordering Information table. Corrected Ordering Information PART information (added hyphen part number). Removed UL#913 bullet from Common iButton Features section. PAGES CHANGED
8/09
Maxim cannot assume responsibility circuitry other than circuitry entirely embodied Maxim product. circuit patent licenses implied. Maxim reserves right change circuitry specifications without notice time.
Maxim Integrated Products, Gabriel Drive, Sunnyvale, 94086 408-737-7600
2009 Maxim Integrated Products Maxim registered trademark Maxim Integrated Products, Inc.
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