Renesas UPD43256BGU-70LL-E2-A

Overview

UPD43256BGU-70LL-E2-A from NEC Electronics is a 256K-bit (32K × 8) CMOS static RAM with 70 ns maximum access time, 4.5–5.5 V supply voltage, and 28-pin plastic SOP package. It features /OE-controlled output enable, low standby current (3 mA), and battery-backed data retention down to 2.0 V - used in industrial control panels requiring nonvolatile memory buffering during power interruption.

For engineers reviewing the UPD43256BGU-70LL-E2-A datasheet, UPD43256BGU-70LL-E2-A pinout, UPD43256BGU-70LL-E2-A application, or UPD43256BGU-70LL-E2-A equivalent, key selection criteria include access time vs. supply voltage range, /CS and /WE timing compatibility with legacy 8-bit microcontrollers, and lead-free SOP-28 footprint alignment with IPC-7351B standard.

Technical Context

The UPD43256BGU-70LL-E2-A implements asynchronous SRAM architecture with full address decoding (A0–A14), bidirectional I/O1–I/O8 bus, and three-level chip enable (/CS), write enable (/WE), and output enable (/OE) control. Its read cycle requires /WE held high while /CS and /OE go active low; write operation occurs only during simultaneous /CS and /WE low states.

It supports two operating modes: active read/write (ICCA1 = 45 mA max at VCC = 4.5–5.5 V) and standby retention (ISB = 3 mA, ICCDR = 0.5–20 μA depending on temperature). Data retention remains valid at VCCDR ≥ 2.0 V with /CS ≥ VCC − 0.2 V, enabling use with backup batteries or supercapacitors.

Key Specifications

Pinout & Package

UPD43256BGU-70LL-E2-A is housed in a 28-pin plastic SOP (Small Outline Package) with 11.43 mm body width and 1.27 mm lead pitch, compliant with JEDEC MS-012AC. Pin 1 index mark is located at top-left corner when marking side faces up.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar static RAM applications.

Compared with AS6C4008-70SCN and IS61LV25616AL-70TQLI, UPD43256BGU-70LL-E2-A offers unique 5 V compatibility, SOP-28 footprint, and 8-bit bus alignment - making it irreplaceable in retrofitting legacy 8-bit industrial controllers without board revision.

Availability

UPD43256BGU-70LL-E2-A is available at Aetrix Electronics and suitable for industrial PLC data buffering, legacy instrumentation memory retention, and embedded HMI display caching requiring stable component supply across extended production lifecycles.

Supply support for UPD43256BGU-70LL-E2-A 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

NEC Electronics Corporation (now part of Renesas Electronics) was a Japanese semiconductor manufacturer specializing in memory, microcontrollers, and analog ICs for industrial and communications markets.

The μPD43256B family was designed for cost-sensitive, reliability-critical embedded systems requiring pin-compatible 5 V SRAM upgrades to replace aging bipolar or NMOS memory devices.

FAQ

What is the maximum clock frequency supported by UPD43256BGU-70LL-E2-A?

UPD43256BGU-70LL-E2-A is an asynchronous static RAM and does not use a clock signal. Its timing is governed by access times: tAA = 70 ns max, tRC = 70 ns max, and tWC = 70 ns max. When interfaced with a microcontroller, the maximum effective bus frequency is ~14.3 MHz (1/70 ns), assuming zero wait states and ideal signal integrity. UPD43256BGU-70LL-E2-A requires no external clock source - all operations are controlled by /CS, /WE, and /OE edge timing.

Does UPD43256BGU-70LL-E2-A support battery backup operation?

Yes, UPD43256BGU-70LL-E2-A supports battery backup via its low-voltage data retention capability. With /CS held ≥ VCC − 0.2 V, it retains data at VCCDR ≥ 2.0 V (min), allowing direct connection to a 3 V lithium coin cell or supercapacitor. The retention current ICCDR is 0.5–20 μA depending on temperature, enabling multi-year backup without recharge. UPD43256BGU-70LL-E2-A requires no external circuitry beyond a diode-OR or switch to isolate main and backup supplies.

What is the meaning of the "-E2-A" suffix in UPD43256BGU-70LL-E2-A?

The "-E2-A" suffix in UPD43256BGU-70LL-E2-A indicates two compliance attributes: "-E2" denotes tape-and-reel packaging per EIA-481-D standard (1,000 units per reel), and "-A" certifies lead-free construction per RoHS Directive 2011/65/EU, including matte tin terminations and halogen-free epoxy molding compound. This suffix confirms UPD43256BGU-70LL-E2-A meets modern environmental and assembly requirements without altering electrical or timing specifications.

Can UPD43256BGU-70LL-E2-A be operated at 3.3 V?

No, UPD43256BGU-70LL-E2-A is specified only for 4.5–5.5 V operation (L-version). Its VIH minimum is 2.2 V, but DC and AC characteristics - including tAA = 70 ns, ICCA1 = 45 mA, and VOL = 0.4 V - are guaranteed exclusively within the 4.5–5.5 V range. Attempting 3.3 V operation risks timing violations, increased leakage, and data corruption. For 3.3 V systems, consider the A-version (e.g., UPD43256BGU-A85) or alternate families like IS61LV25616AL.

How does the /OE pin function during write operations in UPD43256BGU-70LL-E2-A?

In UPD43256BGU-70LL-E2-A, the /OE pin is ignored during write cycles: when /WE is low (write active), the I/O pins are forced into high-impedance regardless of /OE state. /OE only controls output driver enable during read cycles (when /WE is high). This design prevents bus contention during writes and allows /OE to be tied high or controlled independently for read arbitration. UPD43256BGU-70LL-E2-A's truth table explicitly defines /WE dominance over /OE in write mode.