Renesas 71256L55DB

Overview

71256L55DB from Renesas is a 256K (32K × 8-bit) low-power CMOS static RAM with military-grade reliability, 55 ns maximum access time, 2 V data retention capability, and compliance with MIL-STD-883 Class B for operation from –55°C to +125°C. It serves as non-volatile SRAM buffer in avionics control modules requiring persistent memory during brownout.

For engineers reviewing the 71256L55DB datasheet, 71256L55DB pinout, 71256L55DB application, or 71256L55DB equivalent, key selection criteria include military temperature support, battery-backed data retention at 2 V, TTL-compatible I/O, standby current of 1.5 mA (CMOS-level CS), and ceramic DIP package compatibility with legacy high-reliability PCB layouts.

Technical Context

The 71256L55DB implements a full CMOS static memory array with dual power modes: active operation at 5 V ±10% and data retention down to 2 V. Its chip select–driven automatic standby logic transitions I/O to high-impedance when CS goes HIGH, enabling system-level power gating without external control logic.

It supports both WE-controlled and CS-controlled write cycles with defined timing overlap requirements (e.g., tDW = 25 ns min), and features TTL-compatible input thresholds (VIH = 2.2 V min, VIL = 0.8 V max) and output drive (VOL = 0.4 V at 8 mA, VOH = 2.4 V at –4 mA), ensuring interoperability with legacy 5 V logic families.

Key Specifications

Pinout & Package

71256L55DB is housed in a 28-pin 600 mil ceramic dual in-line package (CD28), offering hermetic sealing and thermal stability for harsh-environment deployment. Pin numbering follows standard DIP top-view orientation with Pin 1 in upper-left corner.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar high-reliability SRAM applications.

Compared with IS61LV25616AL-10TLI and AS6C4008-55PCN, the 71256L55DB uniquely delivers MIL-qualified operation, 2 V data retention, and TTL-compatible 5 V I/O in a hermetic ceramic DIP-making it irreplaceable in legacy avionics and defense systems requiring proven reliability over decades.

Availability

71256L55DB is available at Aetrix Electronics and suitable for avionics flight control, tactical radio configuration storage, missile guidance system cache, and spacecraft onboard telemetry buffer applications requiring stable component supply across extended product lifecycles.

Supply support for 71256L55DB 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

Renesas Electronics Corporation is a global semiconductor leader delivering trusted embedded solutions for automotive, industrial, infrastructure, and IoT applications, with deep heritage in high-reliability memory and microcontroller design.

The 71256L55DB belongs to Renesas' legacy high-reliability SRAM product line, engineered specifically for military, aerospace, and industrial systems demanding guaranteed performance across extreme temperatures and long service life.

FAQ

What is the minimum supply voltage required for data retention in the 71256L55DB?

The 71256L55DB guarantees data retention down to 2.0 V (VDR), as specified in Table 11 of the Renesas datasheet. At this voltage, typical data retention current is 120 μA, enabling operation from a single lithium primary cell without regulation. This feature is exclusive to the "L" (low-power) variant and is validated across the full military temperature range (–55°C to +125°C). The 71256L55DB maintains stored data indefinitely as long as VCC remains ≥2.0 V and ambient temperature stays within specification limits.

Does the 71256L55DB support true TTL-level input and output signaling?

Yes, the 71256L55DB features fully TTL-compatible I/O: input high voltage (VIH) is guaranteed ≥2.2 V, input low voltage (VIL) ≤0.8 V, output high voltage (VOH) ≥2.4 V at –4 mA, and output low voltage (VOL) ≤0.4 V at 8 mA. These specifications match standard 74LS logic levels, allowing direct connection to legacy 5 V microcontrollers, FPGAs, and bus controllers without level-shifting circuitry. This compatibility is confirmed in Tables 6 and 10 of the Renesas datasheet.

What is the standby current consumption of the 71256L55DB when CS is asserted at CMOS threshold?

When CS exceeds the CMOS-level high threshold (VHC = VCC – 0.2 V), the 71256L55DB enters full standby mode (ISB1), drawing ≤1.5 mA maximum at VCC = 5.5 V and TA = +25°C, per Table 8 of the Renesas datasheet. This is significantly lower than its TTL-level standby current (ISB = 3 mA max) and enables multi-year battery backup in mission-critical systems. The 71256L55DB automatically transitions to this state without external control signals or clock gating.

Is the 71256L55DB packaged in a hermetic enclosure?

Yes, the 71256L55DB uses a 28-pin 600 mil ceramic dual in-line package (CD28), which is a hermetically sealed ceramic DIP. This construction meets MIL-STD-883 requirements for moisture resistance, thermal stability, and long-term parameter consistency in high-humidity, high-vibration, or corrosive environments. The CD28 package is explicitly listed in the Ordering Information table (page 10) and shown in the Pin Configuration diagram (Figure 2).

How does the 71256L55DB differ from commercial-grade variants like the 71256L25YG?

The 71256L55DB differs from commercial variants such as 71256L25YG in three key ways: (1) it is screened and qualified to MIL-STD-883 Class B, including mechanical shock, vibration, and temperature cycling tests; (2) it operates across –55°C to +125°C, whereas 71256L25YG is rated only from 0°C to +70°C; and (3) it uses a 600 mil ceramic DIP (CD28) instead of a 300 mil SOJ (PJG28), providing superior hermeticity and board-level reliability. These distinctions make the 71256L55DB suitable for defense and aerospace deployments where environmental robustness is mandatory.