Analog Devices Inc./Maxim Integrated DS2505+

Overview

DS2505+ from Maxim Integrated is a 16 kbit add-only EPROM memory IC with factory-lasered 64-bit ROM, operating via 1-Wire® interface on a single data line plus ground. It delivers 16384 bits of user-programmable memory partitioned into 64 × 256-bit pages, supports page-level write protection, and enables software-driven data patching via page address redirection. It reads over 2.8V–6.0V at -40°C to +85°C and programs at 11.5V–12.0V from -40°C to +50°C - used in calibration storage, asset tracking, and maintenance record logging.

For engineers reviewing the DS2505+ datasheet, DS2505+ pinout, DS2505+ application, or DS2505+ equivalent, this page provides verified technical context, exact pin roles for TO-92 package, real-world use cases in traceability systems, and two confirmed alternative parts with documented functional and application differences.

Technical Context

The DS2505+ implements a parasitic-power 1-Wire interface: all read operations draw power from the data line via internal capacitor charge storage, eliminating need for V_DD. Its hierarchical protocol requires ROM function commands (e.g., Read ROM, Search ROM) before enabling memory functions like Read Memory (F0h), Extended Read Memory (A5h), or Write Memory (0Fh/F3h).

Memory architecture comprises three distinct sections: 64-bit lasered ROM (8-bit family code 0Bh + 48-bit serial number + 8-bit CRC), 16384-bit EPROM data memory (64 pages × 32 bytes), and 704-bit EPROM status memory (000h–13Fh) containing write-protect bits, page redirection bytes, and usage flags - all accessible only after ROM command completion.

Key Specifications

Pinout & Package

DS2505+ is supplied in lead(Pb)-free TO-92 package (3.7 × 4.0 × 1.5 mm), compatible with standard tape-and-reel automated assembly. Pin configuration is fixed and validated per Maxim's mechanical drawing.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 1-Wire add-only memory applications.

Compared with DS2505+, DS2502+ offers lower density and no page redirection, limiting its use in versioned data systems; DS2430A+ provides rewritable EEPROM but sacrifices the tamper-evident, laser-programmed uniqueness essential for regulatory traceability.

Availability

DS2505+ is available at Aetrix Electronics and suitable for calibration data storage, asset tracking, and access control systems requiring stable component supply, RoHS-compliant packaging, and long-term obsolescence management.

Supply support for DS2505+ includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Maxim Integrated (now part of Analog Devices) designs precision analog, mixed-signal, and digital ICs for industrial, medical, and communications applications.

The DS2505+ belongs to Maxim's 1-Wire memory product line, engineered specifically for secure, low-pin-count, parasitic-powered identification and immutable data logging in harsh or space-constrained environments.

FAQ

What is the function of the NC pin on the DS2505+?

The NC (No Connect) pin on the DS2505+ is internally unconnected and must remain floating - it serves no electrical or functional role in 1-Wire operation. Unlike some variants, DS2505+ does not repurpose this pin for V_DD or auxiliary control. Connecting it may cause undefined behavior or damage. The DS2505+ derives all operating power parasitically from the DATA line during reads and requires 12 V pulses on that same line for programming.

Does DS2505+ support true random-access reads across all 16384 bits?

Yes, DS2505+ supports random-access reads via the Read Memory (F0h) command with any 2-byte starting address (000h–07FFh). However, due to its 1-Wire serial interface, access latency depends on bit position - reading from address 000h takes less time than reading from 07FFh. The Extended Read Memory (A5h) command adds redirection byte pre-check, enabling software to skip invalid pages before initiating full-page reads - optimizing effective random access in versioned data sets.

How does DS2505+ ensure data integrity during programming?

DS2505+ enforces data integrity through mandatory 16-bit CRC verification before each programming pulse: the bus master computes CRC over command, address, and data bytes; DS2505+ returns its own CRC for comparison. Only upon match does the master apply the 12 V/480 µs pulse. Post-pulse, the master reads back the target byte to confirm correct 1→0 transitions. Speed Write mode (F3h) skips CRC but assumes perfect contact - intended only for controlled production environments.

Can DS2505+ be used without a microcontroller?

No - DS2505+ requires an active 1-Wire bus master (e.g., microcontroller GPIO with precise timing control) to execute ROM and memory function commands. It has no autonomous operation: all reads, writes, and redirections depend on externally generated time slots, reset pulses, and 12 V programming pulses. Standalone use (e.g., direct connection to UART or USB) is impossible without a compliant 1-Wire host controller implementing the full protocol stack including CRC generation and voltage switching.

What is the significance of the 0Bh family code in DS2505+?

The 0Bh family code in DS2505+ identifies it as a member of the DS25xx 1-Wire memory family and dictates protocol compatibility: bus masters use this byte to filter responses during Search ROM and Match ROM operations. It ensures that commands like Read Memory (F0h) or Extended Read Memory (A5h) are only executed on DS2505+-compatible devices - preventing miscommunication in multi-device 1-Wire nets containing sensors, iButtons, or other 1-Wire peripherals with different family codes.