Infineon Technologies CY2305SI-1

Overview

CY2305SI-1 from Cypress Semiconductor is an industrial-grade, 3.3V zero-delay clock buffer IC with PLL-based architecture, designed to distribute one reference clock to five low-skew outputs for CPU, PCI, and SDRAM timing systems. It operates from 10 MHz to 100 MHz (133 MHz in high-drive variants), delivers ±350 ps input-output delay control, 85 ps typical output-to-output skew, and enters <25 µA power-down mode when REF is inactive.

For engineers reviewing the CY2305SI-1 datasheet, CY2305SI-1 pinout, CY2305SI-1 application, or CY2305SI-1 equivalent, this page provides verified electrical specifications, industrial temperature performance (–40°C to +85°C), load-dependent zero-delay tuning guidance, and direct substitution options for legacy Pentium-class embedded clock distribution.

Technical Context

The CY2305SI-1 integrates an on-chip PLL with internal feedback sourced from the CLKOUT pin, enabling precise zero-input-output propagation delay when all outputs-including CLKOUT-are uniformly loaded. Its single-reference, five-output topology eliminates external loop components and supports system-level clock fanout without added jitter accumulation.

It features weak-pull-down outputs, a 5V-tolerant REF input with VDD/2 threshold, and automatic PLL shutdown during REF inactivity-reducing supply current to ≤25 µA. Rise/fall times are guaranteed ≤2.50 ns (10–90%, 0.8V–2.0V) under 30 pF load at 66.67 MHz.

Key Specifications

Pinout & Package

Package: 8-pin, 150-mil SOIC (width = 3.9 mm), surface-mount, RoHS-compliant.

Key Features

Applications

Equivalent & Alternatives

CY2305SI-1 has two documented drop-in alternatives with validated functional and package compatibility.

Compared with CY2305SC-1, the SI-1 offers extended thermal reliability without design change; versus ICS552GI-01LFT, it delivers superior power efficiency and simpler zero-delay implementation at the cost of slightly higher skew.

Availability

CY2305SI-1 is available at Aetrix Electronics and suitable for PCI bus clock distribution, SDRAM controller timing, and Pentium-class CPU support requiring stable component supply across industrial temperature ranges and long production lifecycles.

Supply support for CY2305SI-1 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) is a U.S.-based semiconductor company specializing in timing, memory, and programmable solutions for industrial, automotive, and communications markets.

The CY2305 product line was engineered specifically for cost-sensitive, high-reliability clock fanout in legacy x86 and embedded systems-prioritizing zero-delay accuracy, low power-down current, and industrial temperature robustness.

FAQ

What is the purpose of the CLKOUT pin beyond clock output?

The CLKOUT pin serves as the internal feedback node for the on-chip PLL. Its capacitive load directly controls the input-output propagation delay: matching its load to other outputs achieves zero delay. Even if unused, CLKOUT must be loaded identically to maintain timing accuracy-otherwise, delay shifts up to ±350 ps occur.

Can CY2305SI-1 operate with a 5V input clock while powered at 3.3V?

Yes. The REF pin is explicitly 5V-tolerant per datasheet Absolute Maximum Ratings and Electrical Characteristics. It accepts 0–7V input voltage with a VDD/2 switching threshold, enabling direct connection to 5V logic clocks without level shifters-critical for interfacing with legacy PCI or ISA bus sources.

How does the device achieve zero input-output delay?

Zero delay is achieved through PLL-based feedback where the CLKOUT pin closes the loop. When all outputs-including CLKOUT-are identically loaded (e.g., same trace length, termination, and capacitance), the PLL adjusts phase to cancel propagation delay. Deviations in CLKOUT loading shift delay predictably, as quantified in Figure 3 of the datasheet.

Is external decoupling required for stable operation?

Yes. A minimum 0.1 µF ceramic capacitor must be placed between VDD (Pin 6) and GND (Pin 4), located within 5 mm of the package. This suppresses high-frequency supply noise generated by simultaneous output switching, preventing jitter increase and PLL instability-especially above 66 MHz.