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DS1985
16Kb Add-Only iButton®


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Status
Part Number Status
DS1985 Active: In Production. But some versions of the family are No Longer Available. See Ordering Information.

Data Sheet
FULL DATA SHEET (PDF, 500kB)
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Description
The DS1985 16Kb Add-Only iButton is a rugged read/write data carrier that identifies and stores relevant information about the product or person to which it is attached. This information can be accessed with minimal hardware, for example a single port pin of a microcontroller. The DS1985 consists of a factory-lasered registration number that includes a unique 48-bit serial number, an 8-bit CRC, and an 8-bit Family Code (0BH) plus 16Kb of EPROM which is user-programmable. The power to program and read the DS1985 is derived entirely from the 1-Wire communication line. Data is transferred serially via the 1-Wire protocol which requires only a single data lead and a ground return. The entire device can be programmed and then write-protected if desired. Alternatively, the part may be programmed multiple times with new data being appended to, but not overwriting, existing data with each subsequent programming of the device. Note: Individual bits can be changed only from a logical 1 to a logical 0, never from a logical 0 to a logical 1. A provision is also included for indicating that a certain page or pages of data are no longer valid and have been replaced with new or updated data that is now residing at an alternate page address. This page address redirection allows software to patch data and enhance the flexibility of the device as a standalone database. The 48-bit serial number that is factory-lasered into each DS1985 provides a guaranteed unique identity which allows for absolute traceability. The durable MicroCan package is highly resistant to harsh environments such as dirt, moisture, and shock. Its compact button-shaped profile is self-aligning with cup-shaped receptacles, allowing the DS1985 to be used easily by human operators or automatic equipment. Accessories permit the DS1985 to be mounted on printed circuit boards, plastic key fobs, photo-ID badges, ID bracelets, and many other objects. Applications include work-in-progress tracking, electronic travelers, access control, storage of calibration constants, and debit tokens.

Key Features
  • 16384 bits Electrically Programmable Read Only Memory (EPROM) communicates with the economy of one signal plus ground
  • EPROM partitioned into sixty-four 256-bit pages for randomly accessing packetized data records
  • Each memory page can be permanently write-protected to prevent tampering
  • Device is an "add only" memory where additional data can be programmed into EPROM without disturbing existing data
  • Architecture allows software to patch data by superseding an old page in favor of a newly programmed page
  • Reduces control, address, data, power, and programming signals to a single data pin
  • 8-bit family code specifies DS1985 communications requirements to reader
  • Reads over a wide voltage range of 2.8V to 6.0V from -40°C to +85°C; programs at 11.5V to 12.0V from -40°C to +85°C

Key Specifications:  iButton Products
Part Number Overview Memory Type Memory Size Unique Ware Real Time Clock Smallest Available Pckg.
(mm2)
Price
max w/pins See Notes
DS1985 
iButton Memory
EPROM 16K bits No No 301 $2.07 @1k
See All iButton Products (26)

Diagram

Application Notes
  • Application Note 27: Understanding and Using Cyclic Redundancy Checks with Maxim iButton Products - DS1985
  • Application Note 74: Reading and Writing 1-Wire® Devices Through Serial Interfaces - DS1985
  • Application Note 114: 1-Wire File Structure - DS1985
  • Application Note 126: 1-Wire® Communication Through Software - DS1985
  • Application Note 148: Guidelines for Reliable Long Line 1-Wire® Networks - DS1985
  • Application Note 155: 1-Wire® Software Resource Guide Device Description - DS1985
  • Application Note 159: Software Methods to Achieve Robust 1-Wire® Communication in iButton® Applications - DS1985
  • Application Note 187: 1-Wire Search Algorithm - DS1985
  • Application Note 192: Using the DS2480B Serial 1-Wire Line Driver - DS1985
  • Application Note 244: Advanced 1-Wire Network Driver - DS1985
  • Application Note 937: Book of iButton® Standards - DS1985
  • Application Note 1097: White Paper 2: Using the 1-Wire® Public Domain Kit - DS1985
  • Application Note 1100: White Paper 5: Using 1-Wire APIs for Data Sheet Commands - DS1985
  • Application Note 3808: What Is an iButton? - DS1985

    Design Guides
  • 1-Wire® Products (PDF)

    Reliability Reports
  • Request Reliability Report for:

    Software/Models
    none

    Ordering Information
    Notes:

    1. Other options and links for purchasing parts are listed at: http://www.maxim-ic.com/sales.
    2. Didn't Find What You Need? Ask our applications engineers. Expert assistance in finding parts, usually within one business day.
    3. Part number suffixes: T or T&R = tape and reel;+ = RoHS/lead-free;# = RoHS/lead-exempt. More: SeeFull Data Sheet or Part Naming Conventions.
    4. * Some packages have variations, listed on the drawing. "PkgCode/Variation" tells which variation the product uses. Note that "+", "#", "-" in the part number suffix describes RoHS status. Package drawings may show a different suffix character.


    Devices: 1-6 of 6

    DS1985 Notes Free
    Sample
    Buy Status Recommended Replacement
    Package: TYPE PINS FOOTPRINT
      DRAWING CODE/VAR *
    Temp RoHS/Lead-Free?
    Materials Analysis
    DS1985-F3+  
    Active
    CAN-F3;2 pin;301 mm²
    Outline Drawing: 21-0252 (PDF)
    Land Pattern: Not Available
    Use pkgcode/variation: IB+3NT*
    -40°C to +85°C RoHS/Lead-Free: Lead Free
    Materials Analysis
    DS1985-F5+  
    Active
    CAN-F5;2 pin;301 mm²
    Outline Drawing: 21-0266 (PDF)
    Land Pattern: Not Available
    Use pkgcode/variation: IB+5NT*
    -40°C to +85°C RoHS/Lead-Free: Lead Free
    Materials Analysis
    DS1985-F5   F5 MicroCan   N/A No Longer Available DS1985-F5#


    Land Pattern: Not Available

    -40°C to +85°C See data sheet
    DS1985-F3   F3 MicroCan   N/A No Longer Available DS1985-F3#
    CAN-F3;2 pin;301 mm²
    Outline Drawing: 21-0252 (PDF)
    Land Pattern: Not Available
    Use pkgcode/variation: IB-3NT*
    -40°C to +85°C RoHS/Lead-Free: No
    Materials Analysis
    DS1985-F3#  
    Active
    CAN-F3;2 pin;301 mm²
    Outline Drawing: 21-0252 (PDF)
    Land Pattern: Not Available
    Use pkgcode/variation: IB#3NB*
    -40°C to +85°C RoHS/Lead-Free: RoHS Qualified
    Materials Analysis
    DS1985-F5#  
    Active
    CAN-F5;2 pin;301 mm²
    Outline Drawing: 21-0266 (PDF)
    Land Pattern: Not Available
    Use pkgcode/variation: IB#5NB*
    -40°C to +85°C RoHS/Lead-Free: RoHS Qualified
    Materials Analysis

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    Document Ref.: 19-4892; 2009-09-16
    This page last modified: 2009-09-16


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