Analog Devices Inc./Maxim Integrated DS1249Y-85

Overview

DS1249Y-85 from Maxim Integrated is a 2048k (2,097,152-bit) nonvolatile static RAM organized as 262,144 × 8, featuring ±10% V_CC operation (4.5V–5.5V), 70 ns read/write access time, and integrated lithium battery backup enabling 10-year data retention without external power. It operates in industrial temperature range (–40°C to +85°C) and uses JEDEC-standard 32-pin 740-mil extended DIP package for legacy system memory retention in power-critical embedded controllers.

For engineers reviewing the DS1249Y-85 datasheet, DS1249Y-85 pinout, DS1249Y-85 application, or DS1249Y-85 equivalent, key selection considerations include its automatic V_CC-monitored write protection trigger at 4.25V, unlimited write cycles, CMOS-compatible I/O timing, and self-contained battery freshness seal that activates only on first power-up.

Technical Context

The DS1249Y-85 implements a fully static NV SRAM architecture with on-chip voltage monitoring and analog power-switching circuitry that disconnects the lithium cell until initial V_CC application and re-engages it when V_CC falls below ~3.0V. Its control logic enforces unconditional write protection during brownout, forcing all inputs to "don't care" and outputs to high-impedance.

It supports standard parallel microprocessor bus interfacing with independent CE/WE/OE control, full address decoding across A0–A17 (18-bit), and bidirectional DQ0–DQ7 data lines. Timing compliance includes t_ACC = 70 ns, t_WC = 70 ns, and t_OE = 35 ns under V_CC = 5V ±10%, meeting legacy 8/16-bit system timing budgets without glue logic.

Key Specifications

Pinout & Package

DS1249Y-85 is housed in a JEDEC-standard 32-pin Extended Dual In-line Package (EDIP), 740 mil width, with through-hole mounting and wave/hand-solder compatibility only.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar nonvolatile SRAM applications.

Compared with STK12C68-AW50I and DS1248Y-85, DS1249Y-85 uniquely delivers 10-year retention, industrial temperature qualification, and ±10% V_CC tolerance in a drop-in 32-pin DIP-making it the sole option for retrofitting aging military, utility, and transportation control systems requiring zero-layout-change reliability.

Availability

DS1249Y-85 is available at Aetrix Electronics and suitable for industrial data loggers, smart metering systems, and legacy PLC configuration storage requiring stable component supply over extended production lifecycles.

Supply support for DS1249Y-85 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) is a semiconductor company specializing in precision analog, mixed-signal, and power management ICs for industrial, automotive, and communications markets.

The DS1249Y-85 belongs to Maxim's nonvolatile SRAM product line, designed specifically to replace battery-backed DRAM and EEPROM in mission-critical systems where data integrity during power loss is non-negotiable.

FAQ

What is the guaranteed data retention period for DS1249Y-85?

The DS1249Y-85 guarantees a minimum 10-year data retention period in the absence of external power, based on component selection, process control, and design validation-not production-tested per unit. This retention begins from the moment V_CC is first applied, activating the sealed lithium cell. The DS1249Y-85 achieves this via an internal power-switching circuit that engages the battery only when V_CC drops below ~3.0V.

Does DS1249Y-85 require external circuitry for battery backup operation?

No, DS1249Y-85 requires no external circuitry for battery backup operation. It integrates a lithium energy source, voltage monitor, and analog power-switching circuitry. The lithium cell remains electrically disconnected until first application of V_CC > V_TP (4.25V), ensuring full capacity at deployment. DS1249Y-85 automatically enables write protection and switches to battery power during brownout-no external supervisors, capacitors, or diodes needed.

What is the difference between DS1249Y-85 and DS1249AB-85?

The DS1249Y-85 operates over V_CC = 4.5V–5.5V (±10%) and triggers write protection at V_TP = 4.25V–4.5V, while DS1249AB-85 uses V_CC = 4.75V–5.25V (±5%) and V_TP = 4.50V–4.75V. Both share identical pinout, package, speed (70 ns), and industrial temperature rating. DS1249Y-85 is preferred for systems with wider supply tolerance; DS1249AB-85 suits tightly regulated 5V rails.

Can DS1249Y-85 be used as a direct replacement for standard SRAMs like HM62256?

Yes, DS1249Y-85 is functionally and pin-compatible with 256K×8 SRAMs such as HM62256 in read/write timing and address/data interface-but adds automatic nonvolatile backup. Its CE/WE/OE timing matches standard SRAM protocols, and it drives TTL loads directly. However, DS1249Y-85 requires no external battery or backup controller, making it a true drop-in upgrade for systems needing data retention without redesign.

Is DS1249Y-85 RoHS-compliant?

Yes, DS1249Y-85 is RoHS-compliant, indicated by the "#" suffix in its ordering code (e.g., DS1249Y-70IND#). It conforms to EU Directive 2011/65/EU, including exemptions for lead in glass frits within the ceramic package seal. Aetrix Electronics provides full material declarations and test reports upon request for DS1249Y-85.