Renesas 71V2556S133PFG8

Overview

71V2556S133PFG8 from IDT (now Renesas) is a 128K × 36-bit (4.5 Mbit), 3.3V synchronous ZBT™ SRAM with 2.5V I/O, pipelined outputs, and zero-bus-turnaround architecture. It delivers 166 MHz operation (3.5 ns clock-to-data access), supports 4-word linear/interleaved burst modes via internal counter, and features individual byte write control (BW1–BW4), three chip enables, and optional IEEE 1149.1 JTAG for boundary scan. It is used in high-speed packet buffering and cache applications in networking switches and routers.

For engineers reviewing the 71V2556S133PFG8 datasheet, 71V2556S133PFG8 pinout, 71V2556S133PFG8 application, or 71V2556S133PFG8 equivalent, key selection considerations include its ZBT™ zero-turnaround timing, 100-pin TQFP package with VDDQ/VSS separation, industrial temperature support (–40°C to +85°C), and compatibility with burst-addressed memory controllers requiring deterministic latency and no dead cycles between read/write transitions.

Technical Context

The 71V2556S133PFG8 implements a fully synchronous, clock-edge-triggered architecture with input registers for address, data, and control signals. Its internal burst counter advances on ADV/LD = HIGH and loads external addresses on ADV/LD = LOW, enabling seamless 4-word bursts without external sequencing logic.

ZBT™ operation eliminates bus turnaround overhead by allowing immediate read-after-write or write-after-read transitions within the same clock domain - achieved via internally synchronized OE and pipelined output registers that decouple output enable timing from clock edges.

Key Specifications

Pinout & Package

Packaged in a JEDEC-standard 100-pin plastic thin quad flatpack (TQFP), the 71V2556S133PFG8 uses a 0.5 mm pitch, surface-mount footprint with exposed thermal pad (not electrically connected). Power and ground pins are distributed across all four sides to minimize simultaneous switching noise and improve signal integrity.

Key Features

Applications

Equivalent & Alternatives

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

Compared with CY7C1356BV33-166AXC and AS7C31026B-166JCIN, the 71V2556S133PFG8 uniquely delivers true zero-bus-turnaround operation, integrated burst counter, and pipelined outputs - making it irreplaceable in applications demanding uninterrupted 166 MHz data flow with mixed read/write patterns.

Availability

71V2556S133PFG8 is available at Aetrix Electronics and suitable for network packet buffering, high-speed cache memory, telecom line card memory, and industrial real-time controller buffer applications requiring stable component supply, long-term lifecycle support, and industrial-grade reliability.

Supply support for 71V2556S133PFG8 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, is a leader in high-performance timing, memory, and interface solutions for communications, computing, and industrial markets.

The 71V2556S133PFG8 belongs to IDT's ZBT™ SRAM product line, engineered specifically for zero-latency, burst-oriented memory subsystems in networking infrastructure and real-time embedded systems.

FAQ

What is the ZBT™ feature of the 71V2556S133PFG8 and how does it improve system performance?

The ZBT™ (Zero Bus Turnaround) feature of the 71V2556S133PFG8 eliminates dead cycles between consecutive read and write operations. Unlike conventional SRAMs that require idle cycles to change bus direction, the 71V2556S133PFG8 transitions instantly - enabling sustained 100% bus utilization. This is critical in packet buffering and cache applications where mixed read/write traffic dominates, directly increasing effective throughput without increasing clock frequency.

Does the 71V2556S133PFG8 support both linear and interleaved burst modes, and how is the mode selected?

Yes, the 71V2556S133PFG8 supports both linear and interleaved 4-word burst sequences. The mode is selected by the logic level on the LBO (Linear/Interleaved Burst Order) pin: LBO = VSS selects linear order (A0, A1, A2, A3), while LBO = VDD selects interleaved order (A0, A2, A1, A3). This flexibility allows optimization for sequential vs. cache-line-aligned access patterns without firmware changes.

What are the power supply requirements for the 71V2556S133PFG8, and why are VDD and VDDQ separate?

The 71V2556S133PFG8 requires two supplies: VDD = 3.3 V ±5% for core logic and VDDQ = 2.5 V for I/O buffers. Separating VDD and VDDQ isolates noisy I/O switching transients from sensitive core circuitry, improving signal integrity and reducing crosstalk. It also enables compatibility with 2.5V system buses while maintaining 3.3V internal speed - a key design advantage for mixed-voltage architectures.

How does the 71V2556S133PFG8 handle chip deselection and output tri-state behavior?

When any chip enable (CE1, CE2, or CE2) is deasserted while ADV/LD is LOW, the 71V2556S133PFG8 initiates deselect. Outputs enter high-impedance state exactly two clock cycles after deselect initiation - ensuring clean bus release without glitches. Pending reads or writes complete before tri-state activation, preserving data integrity. This deterministic timing simplifies bus arbitration in multi-SRAM systems.

Is the 71V2556S133PFG8 pin-compatible with other members of the 71V2556 family, such as the 'SA' version?

No - the 71V2556S133PFG8 ('S' version) is not pin-compatible with the 71V2556SA ('SA' version). While both share the same 100-pin TQFP footprint, the 'SA' variant includes dedicated JTAG pins (TMS/TDI/TCK/TDO/TRST) in place of NC pins on the 'S' version. Pin assignments for JTAG-related functions differ, and the 'S' version treats those pins as no-connect. Interchangeability requires verification of board-level routing and JTAG usage requirements.