Infineon Technologies CY7C421-20VXCT

Overview

CY7C421-20VXCT from Cypress Semiconductor is a 512 × 9 asynchronous FIFO memory IC with dual-port RAM architecture, 20 ns access time, 50 MHz max read/write clock rate, TTL-compatible I/O, and standalone/expandable operation for data buffering between mismatched-speed systems. It delivers deterministic latency in serial-to-parallel bridging and protocol translation applications.

For engineers reviewing the CY7C421-20VXCT datasheet, CY7C421-20VXCT pinout, CY7C421-20VXCT application, or CY7C421-20VXCT equivalent, key selection criteria include access time (20 ns), FIFO depth/width (512 × 9), flag behavior (EF/FF/HF), retransmit capability, and width/depth expansion support via XI/XO pins.

Technical Context

The CY7C421-20VXCT implements an asynchronous dual-clock FIFO using a 512-word × 9-bit P-well CMOS RAM array with independent read and write pointers. Its flag logic generates EF (empty), FF (full), and HF (half-full) outputs synchronized to respective control edges, enabling overflow/underflow prevention without external arbitration.

It supports three operational modes: standalone (single device), width expansion (bit-width increase via FL/RT/XI/XO), and depth expansion (capacity increase via cascaded XI→XO chaining). Retransmit functionality is enabled by RT input while R and W are HIGH, allowing repeat readout of the current word without pointer advancement.

Key Specifications

Pinout & Package

Package: 32-pin TQFP (7 mm × 7 mm, 0.5 mm pitch), RoHS-compliant, surface-mount.

Key Features

Applications

Equivalent & Alternatives

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

Compared with IDT7201L20SOI and AM7201-20JC, the CY7C421-20VXCT uniquely integrates retransmit functionality and offers active Pb-free packaging, making it preferable for new designs requiring robust error recovery and RoHS compliance.

Availability

CY7C421-20VXCT is available at Aetrix Electronics and suitable for serial bridging, protocol translation, industrial I/O expansion, and digital acquisition buffering requiring stable component supply and long-term manufacturability.

Supply support for CY7C421-20VXCT 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

Cypress Semiconductor (now part of Infineon Technologies) designs high-reliability memory and programmable logic solutions for industrial, automotive, and communications systems.

The CY7C421 belongs to Cypress's legacy asynchronous FIFO product line, engineered specifically for deterministic data buffering between asynchronous clock domains in embedded control and instrumentation systems.

FAQ

What is the function of the FL/RT pin in depth expansion mode?

In depth expansion mode, FL/RT serves as the First Load input: grounding this pin identifies the first device in the cascade, while tying it to VCC configures subsequent devices. This ensures correct initialization order and prevents race conditions during power-up or reset sequencing across chained FIFOs.

How does the retransmit (RT) feature operate without disrupting pointer positions?

When RT is asserted LOW while R and W are both HIGH, the CY7C421-20VXCT repeats output of the current word at Q0–Q8 without incrementing the read pointer. The internal read address remains unchanged until R goes LOW, preserving data sequence integrity for retry or verification use cases.

Can CY7C421-20VXCT be used in 3.3 V systems?

No - the CY7C421-20VXCT is specified only for 5 V ±10% operation (4.5 V to 5.5 V). Its TTL-compatible inputs require VIH ≥ 2.0 V (commercial) and its outputs drive to VOH ≥ 2.4 V, making direct interfacing with 3.3 V logic unsafe without level translation.

What is the electrical behavior of the XO/HF pin in standalone versus depth expansion configurations?

In standalone mode, XO/HF functions as an active-low half-full flag (asserted when 256 words are stored). In depth expansion, it becomes an active-low expansion out signal that asserts when the current device is full, enabling automatic enablement of the next FIFO in the chain via its XI input.