Renesas 72255LA15TF8

Overview

IDT72255LA15TF8 from Integrated Device Technology (IDT) is a high-speed, 8,192 × 18-bit synchronous CMOS FIFO memory with independent read/write clocks, 15 ns clock cycle time, industrial temperature range (–40°C to +85°C), and Slim Thin Quad Flat Pack (STQFP-64) packaging. It serves as a deep data buffer in high-throughput serial interface bridges between mismatched data rates in telecom line cards.

For engineers reviewing the IDT72255LA15TF8 datasheet, IDT72255LA15TF8 pinout, IDT72255LA15TF8 application, or IDT72255LA15TF8 equivalent, key selection criteria include FWFT/Standard timing mode configurability, programmable almost-empty/full flag offsets, retransmit capability, and dual-clock domain operation without frequency ratio constraints.

Technical Context

This FIFO implements a fully synchronous dual-port architecture with separate RCLK and WCLK domains, eliminating inter-clock frequency dependency - no FS pin required. Its internal RAM array is paired with triple-register-buffered OR output in FWFT mode and double-register-buffered EF/FF in Standard mode for deterministic latency.

The device supports two distinct operational modes selected at Master Reset: IDT Standard (EF/FF flags, REN-gated reads) and First Word Fall Through (OR/IR flags, immediate first-word visibility after three RCLK edges). Flag logic includes independently programmable PAE/PAF thresholds via serial or parallel offset loading using LD, SEN, and WEN control sequences.

Key Specifications

Pinout & Package

Package: 64-pin Slim Thin Quad Flat Pack (STQFP), order code TF, JEDEC MS-026AC compliant, 10 mm × 10 mm body, 0.5 mm lead pitch, exposed thermal pad not present.

Key Features

Applications

Equivalent & Alternatives

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

Compared with IDT72255LA15PF, IDT72255LA15TF8 saves 0.4 mm Z-height for space-constrained modules; compared with NB3N502FG, it delivers 4× depth, 5V compatibility, FWFT timing, and retransmit - making it irreplaceable in high-reliability, high-throughput buffering roles.

Availability

IDT72255LA15TF8 is available at Aetrix Electronics and suitable for telecom infrastructure, industrial protocol gateways, medical imaging subsystems, and broadcast video equipment requiring stable component supply across extended product lifecycles.

Supply support for IDT72255LA15TF8 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) was a fabless semiconductor company specializing in timing, memory interface, RF, and high-performance FIFO solutions before its acquisition by Renesas Electronics in 2019.

IDT72255LA15TF8 belongs to the SuperSync FIFO™ family, designed specifically for deterministic, low-latency data buffering in multi-clock-domain systems such as networking switches, video processing pipelines, and industrial automation controllers.

FAQ

What timing modes does the IDT72255LA15TF8 support, and how is mode selection performed?

The IDT72255LA15TF8 supports two timing modes: IDT Standard and First Word Fall Through (FWFT). Mode selection occurs exclusively during Master Reset (MRS) based on the logic level of the FWFT/SI pin: LOW selects IDT Standard mode (EF/FF flags, REN-gated reads), HIGH selects FWFT mode (OR/IR flags, immediate first-word visibility after three RCLK edges). This configuration is latched and remains fixed until the next MRS assertion.

How does the retransmit (RT) function operate in the IDT72255LA15TF8, and what is its design impact?

The RT input, when asserted on a rising RCLK edge, resets the read pointer to zero without disturbing the write pointer, timing mode, or programmable flag settings. This enables hardware-accelerated rereading of the FIFO's head data - critical for CRC validation, header parsing, or error recovery loops. Unlike software-based pointer manipulation, RT guarantees atomicity and eliminates CPU overhead, preserving real-time determinism in the IDT72255LA15TF8's data path.

Can the programmable almost-empty (PAE) and almost-full (PAF) flags of the IDT72255LA15TF8 be configured after power-up, and what methods are supported?

Yes, PAE and PAF thresholds in the IDT72255LA15TF8 can be reprogrammed at any time after Master Reset using either serial or parallel methods. Parallel programming uses LD + WEN on WCLK edges to load offsets via D0–D17; serial programming uses LD + SEN on WCLK edges to shift 26 bits (LSB-first Empty Offset → MSB Full Offset) via the FWFT/SI pin. The LD pin state during MRS determines the default offset values (127 or 1023) and initial programming method selection.

What is the significance of the DC pin on the IDT72255LA15TF8, and how must it be handled in PCB layout?

DC (Pin 48) is a "Don't Care" terminal on the IDT72255LA15TF8 that must be externally tied to either VCC or GND - it cannot be left floating. Leaving DC unconnected violates the device's absolute maximum ratings and risks metastability or excessive leakage current. In PCB layout, route DC directly to the nearest solid ground or 5V plane using a short, low-inductance trace to ensure stable bias and prevent noise coupling into adjacent signal lines.

Does the IDT72255LA15TF8 support true simultaneous read and write operations, and what clocking constraints apply?

Yes, the IDT72255LA15TF8 supports concurrent read and write operations using fully independent RCLK and WCLK inputs. Crucially, there are no frequency ratio constraints - both clocks may operate from 0 to 66.7 MHz (15 ns cycle time) with arbitrary relative frequencies, phase relationships, or duty cycles. This eliminates the need for external clock domain crossing logic and simplifies system-level timing closure in heterogeneous SoC interconnects.