Renesas 71V2556SA166BG

Overview

71V2556SA166BG 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 operates at 166 MHz (3.5 ns clock-to-data access), supports 4-word linear or interleaved burst mode via LBO control, and features individual byte write (BW1–BW4), three chip enables (CE1/CE2/CE2), and optional IEEE 1149.1 JTAG boundary scan. It is used in high-speed networking packet buffers and cache subsystems requiring deterministic latency and no dead cycles between read/write transitions.

For engineers reviewing the 71V2556SA166BG datasheet, 71V2556SA166BG pinout, 71V2556SA166BG application, or 71V2556SA166BG equivalent, key selection criteria include ZBT timing compliance, TQFP-100 vs. BGA-119 package compatibility, 2.5V I/O voltage tolerance, industrial temperature support (–40°C to +85°C), and JTAG testability for production validation.

Technical Context

The 71V2556SA166BG implements a fully synchronous, clock-edge-triggered architecture with address/data/control registers sampled on the positive clock edge. Its internal burst counter increments on ADV/LD = HIGH and loads external addresses on ADV/LD = LOW, enabling deterministic 4-word burst sequences without external logic.

ZBT operation eliminates bus turnaround dead cycles by allowing immediate read-after-write or write-after-read transitions - achieved via internally synchronized output buffer enable (OE) and pipelined output registers that decouple data output timing from control signal propagation delays.

Key Specifications

Pinout & Package

71V2556SA166BG is packaged in a JEDEC-standard 119-ball grid array (BGA) with 0.8 mm pitch, thermal pad, and ball assignment per BG119 layout. Pin functions are defined for synchronous operation with strict setup/hold timing relative to CLK.

Key Features

Applications

Equivalent & Alternatives

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

Compared with CY7C1356BV166BZC and IS61WV12836BLL-166BLI, the 71V2556SA166BG uniquely delivers zero-bus-turnaround operation, integrated burst counter, and JTAG testability - making it the only viable choice for deterministic-latency, high-throughput packet buffering in telecom infrastructure.

Availability

71V2556SA166BG is available at Aetrix Electronics and suitable for high-speed networking equipment, telecom line cards, and industrial real-time controllers requiring stable component supply, long-term lifecycle support, and traceable sourcing.

Supply support for 71V2556SA166BG 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 fabless semiconductor company specializing in high-performance memory, timing, and interface solutions for communications and computing markets.

The 71V2556SA166BG belongs to IDT's ZBT SRAM product line, designed specifically for applications demanding deterministic latency, zero-bus-turnaround operation, and burst-mode efficiency in packet-processing and cache subsystems.

FAQ

What is the maximum operating frequency and corresponding access time for the 71V2556SA166BG?

The 71V2556SA166BG is rated for a maximum clock frequency of 166 MHz, with a guaranteed clock-to-data access time of 3.5 ns under specified conditions (VDD = 3.3V ±5%, VDDQ = 2.5V, TA = –40°C to +85°C). This timing is achievable only when all synchronous inputs meet setup/hold requirements relative to the CLK rising edge, and the device is operated in its supported industrial temperature range.

Does the 71V2556SA166BG support both linear and interleaved burst modes, and how is the mode selected?

Yes, the 71V2556SA166BG supports both linear and interleaved 4-word burst sequences. The mode is selected via the LBO (Linear/Interleaved Burst Order) pin: connecting LBO to VSS selects linear order (0,1,2,3), while connecting LBO to VDD selects interleaved order (0,2,1,3). This configuration is sampled at the rising edge of CLK and remains effective until changed, enabling runtime burst pattern adaptation in firmware-controlled systems.

What is the function of the three chip enable pins (CE1, CE2, CE2) on the 71V2556SA166BG?

The 71V2556SA166BG uses three chip enable pins - CE1, CE2, and CE2 - to provide flexible depth expansion control. The device is selected only when CE1 = LOW, CE2 = LOW, and CE2 = HIGH. Any deviation (e.g., CE2 = LOW or CE1 = HIGH) deselects the device. This triple-enable scheme allows hierarchical memory bank decoding and supports cascaded configurations without external logic, reducing system complexity in multi-SRAM designs.

Is JTAG boundary scan functionality standard or optional on the 71V2556SA166BG, and which pins are involved?

JTAG boundary scan is an optional feature on the 71V2556SA166BG, implemented per IEEE 1149.1. It uses dedicated pins TMS, TDI, TCK, TDO, and optional TRST - all assigned to NC balls on the "S" version but functional on the "SA" version (as indicated by the "A" suffix in 71V2556SA166BG). These pins are pulled up internally to VDD when unused, and TRST may be left floating if not required, simplifying board design while retaining test flexibility.

How does the 71V2556SA166BG achieve zero-bus-turnaround (ZBT) behavior, and what system-level benefit does it provide?

The 71V2556SA166BG achieves ZBT behavior through its internal architecture: the output buffer enable is synchronized to the clock, eliminating asynchronous OE timing constraints, and the burst counter allows immediate transition from write to read (or vice versa) within the same burst sequence. This removes traditional bus idle cycles, enabling continuous 166 MHz data flow - a critical advantage in packet buffering where back-to-back read/write operations dominate, directly increasing effective memory bandwidth by up to 30% over conventional synchronous SRAMs.