Analog Devices Inc./Maxim Integrated DS2227-100

Overview

DS2227-100 from Maxim Integrated (formerly Dallas Semiconductor) is a 4-Mbit nonvolatile static RAM module in a 72-pin SIP Stik format, organized as 512k × 8, 256k × 16, or 128k × 32 bits, with 100 ns access time, JEDEC-standard SIMM interface, and integrated lithium backup for >10-year data retention without VCC - used in industrial control memory logging and legacy system NVRAM upgrades.

For engineers reviewing the DS2227-100 datasheet, DS2227-100 pinout, DS2227-100 application, or DS2227-100 equivalent, key selection criteria include its self-contained NV SRAM architecture, dual-battery redundancy, automatic write protection below 4.25 V, 72-pin SIMM compatibility, and seamless drop-in replacement capability for standard 5V SRAM sockets requiring persistent storage.

Technical Context

The DS2227-100 integrates four independent SRAM banks (each 128k × 8), each with dedicated CE/WE/OE pins, enabling flexible byte/word/long-word access via external pin tying. Its nonvolatile circuitry operates transparently - no host software changes required - and includes precision voltage monitoring to trigger automatic write protection and lithium switchover at ~3.0 V.

Data retention relies on two isolated lithium cells with internal voltage-selection logic; battery status is verifiable via a three-step read-write-read sequence. The device guarantees functional operation only above 4.5 V VCC, and enforces high-impedance outputs and "don't care" inputs during brownout transitions.

Key Specifications

Pinout & Package

DS2227-100 uses a 72-pin Single-In-Line Package (SIP) Stik with 4.25-inch length, 0.85-inch height, and 0.1-inch pin pitch. Pin 1 = VCC; Pins 50 & 72 = GND; 17 address lines (A0–A16); eight I/O groups (1-D0–1-D7 through 4-D0–4-D7); and per-bank control signals (CE/WE/OE).

Key Features

Applications

Equivalent & Alternatives

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

Compared with STK12C68 and DS1248, the DS2227-100 uniquely delivers dual-battery redundancy, SIMM-compatible 72-pin SIP packaging, and flexible multi-width memory organization - making it the only option supporting both legacy socket reuse and mission-critical data retention assurance.

Availability

DS2227-100 is available at Aetrix Electronics and suitable for industrial PLC data logging, medical device configuration storage, and avionics black box memory buffering requiring stable component supply, long-term obsolescence management, and JEDEC-compliant SIMM form factor compatibility.

Supply support for DS2227-100 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 (acquired by Analog Devices in 2021) is a U.S.-based semiconductor company specializing in analog, mixed-signal, and nonvolatile memory solutions for industrial, medical, and communications markets.

The DS2227-100 belongs to Maxim's Flexible NV SRAM Stik product line, designed specifically to replace volatile SRAM in legacy systems while delivering guaranteed 10-year data retention - targeting applications where firmware cannot be modified but hardware persistence is mandatory.

FAQ

What memory organizations does the DS2227-100 support?

The DS2227-100 supports three configurations: 128k × 32 bits, 256k × 16 bits, or 512k × 8 bits. This flexibility is achieved by externally tying corresponding data, chip enable, read enable, and write enable pins across its four internal SRAM banks. No internal register programming is required - configuration is purely hardware-based via PCB routing.

How does the DS2227-100 ensure data retention during power loss?

The DS2227-100 ensures data retention by automatically switching to an onboard lithium energy source when VCC drops below ~3.0 V. It contains two isolated lithium cells with internal voltage-selection logic, so if one fails, the other takes over seamlessly. Data retention exceeds 10 years without external power, verified per manufacturer testing from date of manufacture.

Is the DS2227-100 pin-compatible with standard 72-pin SIMM sockets?

Yes, the DS2227-100 uses the JEDEC-standard 72-position SIMM connection scheme and is mechanically compatible with industry-standard sockets such as AMP part number 821824-8. Its 72-pin SIP Stik form factor matches height and pin pitch specifications, enabling direct insertion without adapter or modification.

What happens to the DS2227-100 when VCC falls below 4.25 V?

When VCC falls below 4.25 V, the DS2227-100 activates automatic write protection: all inputs become "don't care", outputs go high-impedance, and the device prevents any further writes. This behavior safeguards against partial or corrupted writes during brownout conditions - a hardware-enforced safety feature independent of host control.

Can battery health be verified on the DS2227-100 in-system?

Yes, battery health on the DS2227-100 can be verified in-system using a three-step process: first read any memory location, then write new data to that location, and finally read again. If the second read fails to return the written value, the lithium supply has dropped below 2.0 V and data retention is no longer assured - enabling field-level diagnostics without external test gear.