Winbond Electronics Corporation W955D8MBYA6I TR

Overview

W955D8MBYA6I TR from Winbond Electronics is a 32Mb HyperRAM device implementing the HyperBus DDR interface for high-speed, low-pin-count external memory expansion in resource-constrained embedded systems. It operates at 1.8V, supports up to 166MHz clock frequency (333 MT/s), features configurable wrapped burst lengths (16–128 bytes), and delivers read/write access with initial latency controlled via RWDS signaling. It is used in microcontroller-based HMI displays requiring fast frame buffer access with minimal I/O footprint.

For engineers reviewing the W955D8MBYA6I TR datasheet, W955D8MBYA6I TR pinout, W955D8MBYA6I TR application, or W955D8MBYA6I TR equivalent, this page provides verified technical context, ball-level interface mapping, power-saving mode behavior, burst configuration options, and validated alternative parts for memory subsystem design and BOM optimization.

Technical Context

The W955D8MBYA6I TR implements a DDR HyperBus interface with differential clock (CK/CK#), 8-bit bidirectional DQ[7:0], and bidirectional RWDS acting as both read data strobe and write data mask. All transactions begin with CS# assertion and six-cycle Command-Address (CA) transfer, where CA bits define R/W#, address space (memory/register), burst type, and row/column targeting.

Initial access latency is dynamically indicated by RWDS during CA phase: Low = single latency count, High = double latency count. Memory supports partial array refresh, hybrid sleep, and deep power down modes - all configured via two dedicated registers accessible over the same HyperBus interface.

Key Specifications

Pinout & Package

W955D8MBYA6I TR uses a 24-ball TFBGA package (5 mm × 5 mm, 0.8 mm pitch), ball-down mounting. Pin assignment follows JEDEC MO-270AB standard with defined signal roles and RFU (Reserved for Future Use) balls left unconnected.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar HyperBus memory applications.

Compared with W955D8MBYA6I TR, the Cypress alternative offers identical functionality with mechanical layout trade-offs, while the Infineon part serves a fundamentally different use case - nonvolatile code storage versus volatile high-speed memory - making it unsuitable for frame buffer or runtime data applications.

Availability

W955D8MBYA6I TR is available at Aetrix Electronics and suitable for industrial HMI display buffers, automotive digital clusters, and IoT gateway code storage requiring stable component supply, long-term lifecycle support, and guaranteed traceability.

Supply support for W955D8MBYA6I TR 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

Winbond Electronics is a Taiwan-based semiconductor company specializing in specialty memory solutions including SPI NOR, Serial NAND, and HyperRAM products since 1987.

The W955D8MBYA6I TR belongs to Winbond's HyperRAM family - designed specifically to replace legacy PSRAM in bandwidth-constrained, pin-limited embedded systems while maintaining DDR performance and simplified interface logic.

FAQ

What is the exact memory organization of the W955D8MBYA6I TR?

The W955D8MBYA6I TR is organized as 4,194,304 words × 8 bits (32Mb total), with internal row/column addressing supporting 22-bit row and 10-bit column resolution. This structure enables efficient 16-word (32-byte) page-aligned accesses and matches typical MCU cache line sizes for optimal burst efficiency.

Does the W955D8MBYA6I TR support true random write without erase cycles?

Yes, the W955D8MBYA6I TR is a pseudo-static RAM (PSRAM) device and supports full byte- and word-level random writes at bus speed without sector erasure or wear leveling. Write operations use RWDS as a per-byte mask, allowing precise data merging within a burst - a key distinction from NOR/NAND flash alternatives.

How does RWDS function during a read transaction of the W955D8MBYA6I TR?

During a read transaction, RWDS serves as a source-synchronous read data strobe: the W955D8MBYA6I TR drives RWDS edge-aligned with each 16-bit data word, with byte A aligned to the rising edge and byte B to the falling edge. This eliminates setup/hold timing constraints on the host side and enables reliable high-speed capture.

Can the W955D8MBYA6I TR operate at 166MHz across its full temperature range?

Yes, the W955D8MBYA6I TR is fully rated for 166MHz operation from -40°C to +85°C case temperature. The datasheet specifies tACC ≤ 6 ns and tDSH ≥ 0.35 ns across this range, ensuring timing margin compliance without derating - critical for automotive and industrial deployments.

What is the purpose of the RFU balls on the W955D8MBYA6I TR package?

The RFU (Reserved for Future Use) balls on the W955D8MBYA6I TR - located at A3, A4, B3, B4, C2, and D2 per the ball assignment diagram - are unconnected internally and must remain un-routed on the PCB. They preserve compatibility with future pin-compatible variants that may add signals such as additional VCCQ or debug interfaces.