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Status
Part Number	Status	Replacement	Explanation
DS1991	This product is Not Recommended for New Designs. See Ordering Information for recommended replacements.	DS1977	DS1991 is only available under allocation due to end of life program. Recommended alternatives will require software/firmware updates to existing systems.

Data Sheet

FULL DATA SHEET (PDF, 744kB) Download   E-Mail

Description

The DS1991 MultiKey iButton® is a rugged read/write data carrier that acts as three separate electronic keys, offering 1,152 bits of secure, nonvolatile memory. Each key is 384 bits long with distinct 64-bit password and public ID fields (Figure 1). The password field must be matched in order to access the secure memory. Data is transferred serially via the 1-Wire® protocol, which requires only a single data lead and a ground return. The 512-bit scratchpad serves to ensure integrity of data transfers to secure memory. Data should first be written to the scratchpad where it can be read back. After the data has been verified, a copy scratchpad command will transfer the data to the secure memory. This process ensures data integrity when modifying the memory. A 48-bit serial number is factory lasered into each DS1991 to provide a guaranteed unique identity which allows for absolute traceability. The family code for the DS1991 is 02h. The durable MicroCan package is highly resistant to environmental hazards such as dirt, moisture and shock. Its compact button-shaped profile is self-aligning with mating receptacles, allowing the DS1991 to be easily used by human operators. Accessories permit the DS1991 to be mounted on plastic key fobs, photo-ID badges, printed-circuit boards or any smooth surface of an object. Applications include secure access control, debit tokens, work-in-progress tracking, electronic travelers and proprietary data.

This product contains lithium-metal batteries. See applicable regulations for transport requirements for batteries in equipment.

Key Features		Applications/Uses
1,152-bit secure read/write, nonvolatile memory Secure memory cannot be deciphered without matching 64-bit password Memory is partitioned into 3 blocks of 384 bits each 64-bit password and ID fields for each memory block 512-bit scratchpad ensures data transfer integrity Operating temperature range: -40°C to +70°C Over 10 years of data retention Underwriters Laboratories (UL®) Recognized		Guarding Sensitive Financial or Personnel Files Protecting Intellectual Property, such as Licensed Software Restricting Access to Buildings, Cash Drawers, or Maintenance Areas

Diagram

Application Notes

Application Note 74: Reading and Writing 1-Wire® Devices Through Serial Interfaces - DS1991 Application Note 155: 1-Wire® Software Resource Guide Device Description - DS1991 Application Note 937: Book of iButton® Standards - DS1991

Reliability Reports

Reliability Report: DS1991.pdf Underwriters Laboratories (UL®) Recognized

Software/Models

none

Ordering Information

Notes: Other options and links for purchasing parts are listed at: http://www.maxim-ic.com/sales. Didn't Find What You Need? Ask our applications engineers. Expert assistance in finding parts, usually within one business day. Part number suffixes: T or T&R = tape and reel;+ = RoHS/lead-free;# = RoHS/lead-exempt. More: SeeFull Data Sheet or Part Naming Conventions. * 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: 1-11 of 11

DS1991	Free Sample	Buy	Status	Recommended Replacement	Package: TYPE PINS FOOTPRINT   DRAWING CODE/VAR *	Temp	RoHS/Lead-Free? Materials Analysis
DS1991L+004-000		N/A	NRND	DS1977	Land Pattern: Not Available	0°C to +70°C	See data sheet
DS1991L-003-0000		N/A	NRND	DS1991L-003-0000+	Land Pattern: Not Available	0°C to +70°C	See data sheet
DS1991L-004-000		N/A	NRND	DS1991L+004-000	Land Pattern: Not Available	0°C to +70°C	See data sheet
DS1991L-702-00A		N/A	NRND	DS1991L-702-00A+	Land Pattern: Not Available	0°C to +70°C	See data sheet
DS1991L-702-00A+		N/A	NRND	DS1977	Land Pattern: Not Available	0°C to +70°C	See data sheet
DS1991L-F5		N/A	NRND	DS1991L-F5+	Land Pattern: Not Available	0°C to +70°C	See data sheet
DS1991L-F5/A1A		N/A	NRND	DS1991L-F5+A1A	Land Pattern: Not Available	0°C to +70°C	See data sheet
DS1991L-004-000+		N/A	No Longer Available		Land Pattern: Not Available	0°C to +70°C	See data sheet
DS1991L-702-00B+		N/A	No Longer Available		Land Pattern: Not Available	0°C to +70°C	See data sheet
DS1991L-F5+A1A		N/A	No Longer Available		Land Pattern: Not Available	0°C to +70°C	See data sheet
DS1991L-F5+			NRND	DS1977	CAN-F5;2 pin;301 mm² Outline Drawing: 21-0266 (PDF) Land Pattern: Not Available Use pkgcode/variation: IB+5BW*	0°C to +70°C	RoHS/Lead-Free: Lead Free Materials Analysis

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