Infineon Technologies CY23FS04ZXI-3T

Overview

CY23FS04ZXI-3T from Cypress Semiconductor is a FailSafe™ zero-delay clock buffer with dual reference inputs, four phase-aligned LVCMOS outputs, internal digitally controlled crystal oscillator (DCXO), 35 ps max RMS jitter, and 166.7 MHz max output frequency. It serves as a fault-tolerant clock distribution device in telecom line cards requiring uninterrupted timing during primary reference failure.

For engineers reviewing the CY23FS04ZXI-3T datasheet, CY23FS04ZXI-3T pinout, CY23FS04ZXI-3T application, or CY23FS04ZXI-3T equivalent, key selection criteria include DCXO holdover capability, FAIL#/SAFE flag timing, REFSEL-controlled reference switching, and VDD/VDDC dual-supply configuration for industrial-grade clock resilience.

Technical Context

The device implements a DCXO as its primary clock source-phase-aligned to an external reference via feedback (FBK)-eliminating glitching during reference loss. Its PLL is permanently driven by the DCXO, not the reference input, enabling seamless failover without switching transients.

FailSafe operation relies on S[2:1]-configured integer reference-to-crystal ratios (e.g., ×1, ×2, ×6), with capture range determined by crystal C0/C1 ratio and ±300 ppm digital tuning. The FAIL#/SAFE pin asserts within 2×t_REF×n + 25 ns when reference drifts beyond ±300 ppm.

Key Specifications

Pinout & Package

Package: 16-pin TSSOP (thin shrunk small outline package), 5.0 mm × 4.4 mm × 1.2 mm body, 0.65 mm pitch.

Key Features

Applications

Equivalent & Alternatives

Cypress CY23FS04ZXI-3T has two verified drop-in alternatives with documented functional trade-offs.

Compared with Si5332A-D-GM and ICS853S04I-31LFT, CY23FS04ZXI-3T uniquely integrates DCXO-based holdover, hardware-driven FAIL#/SAFE signaling, and zero-delay phase alignment - making it the only choice for applications demanding autonomous, glitch-free clock continuity without software intervention.

Availability

CY23FS04ZXI-3T is available at Aetrix Electronics and suitable for telecom line cards, industrial PLC backplanes, and network switch control planes requiring stable component supply, long-term lifecycle assurance, and fail-safe timing resilience.

Supply support for CY23FS04ZXI-3T 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 timing, memory, and programmable logic solutions for industrial, automotive, and communications infrastructure.

The CY23FS04 family targets mission-critical clock distribution systems where continuous operation during reference failure is mandatory - emphasizing hardware-based failover, low-jitter buffering, and industrial temperature robustness.

FAQ

What crystal specifications are required for reliable DCXO holdover?

The CY23FS04ZXI-3T requires a parallel-resonant fundamental-mode crystal with C0/C1 ≤ 240, nominal load capacitance of 12–14 pF, and manufacturing tolerance ≤ ±15 ppm. Recommended motional capacitance C1 is 10–30 fF; shunt capacitance C0 is 3–7 pF. Pull range must exceed ±300 ppm after accounting for board parasitics and aging.

How does the FAIL#/SAFE pin behave during reference recovery?

FAIL#/SAFE deasserts after tFSH = 12×t_REF×n + 25 ns (min) once the reference frequency re-enters the DCXO capture range. The device automatically resynchronizes the DCXO to the restored reference without interrupting output clocks - no reset or reconfiguration is needed.

Can VDD and VDDC be powered from the same 3.3 V rail?

No. VDDC must be 3.3 V, but VDD may be 2.5 V or 3.3 V. Even when both are 3.3 V, they must be supplied from separate filtered rails: VDDC powers sensitive analog DCXO/PLL circuitry, while VDD drives digital outputs. Mixing rails increases jitter and risks FAIL#/SAFE false assertion.

Is FBK connection mandatory for zero-delay operation?

Yes. One output (e.g., CLKA1) must be connected to FBK to close the phase-lock loop. Without this feedback, the device operates in open-loop mode with uncontrolled phase offset and no zero-delay guarantee. The FBK path must be routed with controlled impedance and minimal stub length to avoid jitter degradation.