Renesas 71V3557S85BG

Overview

71V3557S85BG from Integrated Device Technology is a 128K × 36-bit, 4.5 Mbit synchronous ZBT™ SRAM with 3.3V core/I/O supply, 100 MHz operation (7.5 ns clock-to-data), flow-through outputs, and 4-word burst capability. It supports linear/interleaved burst order via LBO pin and features zero bus turnaround for high-speed memory subsystems in network packet buffers and cache controllers.

For engineers reviewing the 71V3557S85BG datasheet, 71V3557S85BG pinout, 71V3557S85BG application, or 71V3557S85BG equivalent, key selection criteria include ZBT™ timing compliance, TQFP-100 package compatibility, synchronous burst control (ADV/LD, LBO), individual byte write (BW1–BW4), and JTAG boundary scan support per IEEE 1149.1.

Technical Context

The 71V3557S85BG implements a synchronous dual-edge-triggered architecture where address/control inputs are registered on the rising CLK edge, and data output is flow-through (no output register). Burst sequencing is managed by an internal counter advanced by ADV/LD, with order selected statically by LBO.

It integrates three chip enables (CE1, CE2 active-low; CE2 active-high) for depth expansion, Clock Enable (CEN) for full-cycle suspension, and optional IEEE 1149.1 JTAG test interface with TMS/TDI/TCK/TDO/TRST pins. Sleep mode (ZZ) gates internal clock to minimize power while retaining data.

Key Specifications

Pinout & Package

Packaged in JEDEC-standard 100-pin thin quad flatpack (TQFP), 14 mm × 20 mm body, 0.5 mm pitch. Pin 1 marked by corner notch; top-side marking includes "71V3557S85BG" and date code.

Key Features

Applications

Equivalent & Alternatives

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

Compared with CY7C1355BV18-100BZI and AS7C31026B-10JIN, the 71V3557S85BG delivers higher effective bandwidth via ZBT™ and burst, supports wider 36-bit data paths, and provides integrated JTAG - making it optimal for high-performance, testable memory subsystems requiring minimal glue logic.

Availability

71V3557S85BG is available at Aetrix Electronics and suitable for packet buffering, cache controller design, and industrial data logging requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for 71V3557S85BG 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

Integrated Device Technology (IDT), now part of Renesas Electronics, is a fabless semiconductor company specializing in timing, memory interface, RF, and power management ICs for communications, computing, and industrial markets.

The 71V3557S85BG belongs to IDT's ZBT™ SRAM product line, engineered specifically for zero-latency memory subsystems in high-speed networking, storage, and real-time embedded systems demanding deterministic timing and burst efficiency.

FAQ

What is the memory organization and total capacity of the 71V3557S85BG?

The 71V3557S85BG is organized as 128K × 36 bits, delivering a total capacity of 4,718,592 bits (4.5 Mbit). It is pin-compatible with the 256K × 18-bit variant (71V3559S85BG), allowing layout reuse across density options. Both configurations share identical timing, packaging, and feature sets including ZBT™, burst, and JTAG.

Does the 71V3557S85BG support both linear and interleaved burst modes?

Yes, the 71V3557S85BG supports both burst orders via the LBO (Linear/Interleaved Burst Order) pin. When LBO = LOW, the device executes linear bursts (A0, A1, A2, A3); when LBO = HIGH, it executes interleaved bursts (A0, A1, A3, A2). This static configuration must remain stable during operation and is validated in the Interleaved and Linear Burst Sequence Tables of the datasheet.

How does the ZBT™ feature improve system performance compared to standard synchronous SRAMs?

The ZBT™ (Zero Bus Turnaround) feature in the 71V3557S85BG eliminates idle cycles when switching between read and write operations. Unlike conventional SRAMs requiring turnaround cycles, the 71V3557S85BG permits immediate back-to-back reads and writes at full clock rate - sustaining up to 100 million transactions per second in mixed-access patterns typical of packet buffers and cache controllers.

Can the 71V3557S85BG operate with only two chip enables, or are all three required?

The 71V3557S85BG requires all three chip enables (CE1, CE2, CE2) to be asserted for normal operation: CE1 = LOW, CE2 = LOW, and CE2 = HIGH. Deselection occurs if any one is violated (e.g., CE1 = HIGH or CE2 = LOW). This asymmetric enable scheme enables flexible depth expansion without external logic - for example, stacking multiple devices using CE2 as a global enable and CE1/CE2 for individual selection.

Is JTAG boundary scan mandatory, or can the test pins be left unconnected?

JTAG is optional in the 71V3557S85BG. Pins TMS, TDI, TCK, TDO, and TRST are fully compliant with IEEE 1149.1 but may be left unconnected if not used. TRST is internally pulled up and can float; TMS has an internal pull-up, TDI/TCK have internal pull-ups, and TDO is high-impedance when JTAG is inactive. No external termination is required for non-JTAG use.