Renesas 71V2556SA100BG8

Overview

71V2556SA100BG8 from IDT (now Renesas) is a 3.3V synchronous ZBT™ SRAM with 128K × 36-bit (4.5 Mbit) organization, 166 MHz operation (3.5 ns clock-to-data access), and pipelined outputs. It supports zero-bus-turnaround (ZBT) for dead-cycle-free read/write transitions and features 2.5V I/O supply, individual byte write control (BW1–BW4), and optional IEEE 1149.1 JTAG boundary scan. Used in high-speed network packet buffers and telecom line-card data paths.

For engineers reviewing the 71V2556SA100BG8 datasheet, 71V2556SA100BG8 pinout, 71V2556SA100BG8 application, or 71V2556SA100BG8 equivalent, key selection criteria include ZBT timing compliance, TQFP-100 package compatibility, burst counter behavior (linear/interleaved via LBO), 3.3V core / 2.5V I/O voltage separation, and industrial temperature support (–40°C to +85°C).

Technical Context

This device implements a fully synchronous, clock-edge-triggered architecture with address/data/control registers aligned to the rising edge of CLK. Its internal burst counter enables four-word bursts per address load, with sequence direction (linear or interleaved) controlled by the LBO pin level.

The ZBT architecture eliminates bus turnaround latency by allowing immediate read-after-write or write-after-read transitions without wait states. Output enable (OE) is asynchronous but internally synchronized, and chip enable logic (CE1, CE2, CE2) supports depth expansion with tri-state hold on deselection.

Key Specifications

Pinout & Package

Packaged in JEDEC-standard 100-pin thin quad flatpack (TQFP), 14 mm × 20 mm body, 0.5 mm pitch. Pin 64 supports ZZ (sleep mode) on latest die revision.

Key Features

Applications

Equivalent & Alternatives

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

Compared with CY7C1356BV18-167AXC and AS7C33128P-10BIN, the 71V2556SA100BG8 uniquely delivers ZBT timing, pipelined outputs, and industrial-temperature operation in a single TQFP-100 package - making it optimal for latency-critical, high-reliability buffering where bus efficiency and deterministic timing are mandatory.

Availability

71V2556SA100BG8 is available at Aetrix Electronics and suitable for network packet buffers, telecom line cards, and industrial PLC data loggers requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for 71V2556SA100BG8 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

IDT (Integrated Device Technology), now part of Renesas Electronics, specializes in high-performance timing, memory, and interface solutions for communications and computing infrastructure.

The 71V2556SA100BG8 belongs to IDT's ZBT SRAM product line, designed specifically for low-latency, high-bandwidth buffering in telecom, networking, and baseband processing systems demanding zero-bus-turnaround performance.

FAQ

What is the ZBTTM feature of the 71V2556SA100BG8 and how does it improve system performance?

The ZBTTM (Zero Bus Turnaround) feature of the 71V2556SA100BG8 eliminates idle cycles when switching between read and write operations. Unlike conventional SRAMs that require turnaround time to tri-state the bus, the 71V2556SA100BG8 allows immediate back-to-back read/write transitions. This sustains full 166 MHz throughput in burst-intensive applications like packet buffering, directly improving effective bandwidth and reducing controller wait states.

Does the 71V2556SA100BG8 support both linear and interleaved burst modes, and how is this selected?

Yes, the 71V2556SA100BG8 supports both linear and interleaved 4-word burst sequences. The selection is controlled by the LBO (Linear/Interleaved Burst Order) pin: LBO = VSS enables linear order (0,1,2,3), while LBO = VDD enables interleaved order (0,2,1,3). This flexibility allows optimization for different memory access patterns - linear for sequential streaming, interleaved for cache-line-aligned fetches - without firmware changes.

What are the power supply requirements for the 71V2556SA100BG8, and can VDD and VDDQ be powered independently?

The 71V2556SA100BG8 requires two independent supplies: VDD = 3.3 V ±5% for core logic and VDDQ = 2.5 V for I/O circuits. These supplies must be decoupled separately and may be sequenced in any order - no strict power-up sequence is mandated. This separation reduces I/O noise coupling into the core and enables interoperability with 2.5V FPGA or ASIC interfaces while maintaining 3.3V logic robustness.

Is JTAG boundary scan functionality enabled by default on the 71V256SA100BG8, and what pins are used?

JTAG boundary scan is optional on the 71V2556SA100BG8 and disabled by default. When enabled, it uses five dedicated pins: TMS, TDI, TCK, TDO, and TRST (all located on the TQFP-100 package's U-row). These pins are NC on the base "S" version but functional on the "SA" variant (like 71V2556SA100BG8). TRST is optional and may be left floating if not needed, as it is internally pulled to VDD.

How does the 71V2556SA100BG8 handle chip deselection, and what happens to ongoing data transfers?

When any chip enable (CE1, CE2, or CE2) is deasserted while ADV/LD is low, the 71V2556SA100BG8 halts initiation of new memory operations but completes all pending read or write transfers. The data bus enters high-impedance state two clock cycles after deselection is recognized. This ensures data integrity during dynamic depth expansion or partial memory disable scenarios without corrupting in-flight transactions.