Infineon Technologies CY26121KZI-21

Overview

CY26121KZI-21 from Cypress Semiconductor is a Spread Spectrum Clock Generator with integrated PLL, operating at 3.3 V and accepting a 25-MHz crystal or driven reference input. It delivers selectable 33.33-MHz or 25-MHz outputs with –2.8% downspread modulation at 30-kHz nominal frequency, housed in a 16-pin TSSOP package rated for –40°C to +85°C industrial operation.

For engineers reviewing the CY26121KZI-21 datasheet, CY26121KZI-21 pinout, CY26121KZI-21 application, or CY26121KZI-21 equivalent, this device supports EMI reduction in high-speed digital systems including PC motherboards, graphics controllers, and embedded computing platforms where jitter-controlled clocking and thermal stability are critical.

Technical Context

The CY26121KZI-21 implements a dedicated analog PLL with spread-spectrum modulation control logic, generating two independent clock outputs (CLKA–CLKD) referenced to a single 25-MHz input. Its flash-configurable architecture enables fixed-frequency selection via CLKSEL pin state without external programming.

It supports dual crystal load options (6 pF or 15 pF), uses separate analog/digital supply domains (AVDD/VDD/VDDL), and integrates weak-pullup inputs for CLKSEL and SSON - enabling hardware-selectable output frequency and spread-spectrum enable/disable without external biasing.

Key Specifications

Pinout & Package

Package: 16-pin Thin Shrink Small Outline Package (TSSOP), 4.4 mm body width, 0.65 mm pitch, JEDEC MO-153 compliant.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar spread-spectrum clock generator applications.

Compared with IDT 8T49N241 and ON Semi NB3N3020B, the CY26121KZI-21 uniquely balances hardware-selectable spread-spectrum operation, industrial temperature rating, and zero-configuration deployment - making it optimal for cost-sensitive, fixed-function embedded timing applications.

Availability

CY26121KZI-21 is available at Aetrix Electronics and suitable for PC motherboard clocking, graphics controller timing, and industrial PLC CPU timing requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for CY26121KZI-21 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-performance mixed-signal ICs for timing, connectivity, and programmable systems, with global manufacturing and quality certifications.

The CY26121 belongs to Cypress's PacketClock™ family, engineered specifically for EMI-reduction in high-speed digital systems through deterministic spread-spectrum clock generation without software overhead.

FAQ

What is the function of the SSON pin on CY26121KZI-21?

The SSON pin (Pin 10) is an active-high spread-spectrum enable control. When driven high (or left floating, due to internal weak pull-up), it activates the –2.8% downspread modulation at 30 kHz. When pulled low, the device operates in fixed-frequency mode with no spectral spreading. This allows runtime EMI control without changing clock frequency or requiring reconfiguration.

Can CY26121KZI-21 use a 25-MHz oscillator instead of a crystal?

Yes - the XIN pin accepts either a 25-MHz fundamental parallel-resonant crystal (with 15-pF load) or a CMOS-level 25-MHz clock signal. When using an external oscillator, XOUT must be left unconnected per datasheet Note 1. The internal oscillator circuitry is bypassed, and the device locks directly to the applied reference.

How does the CY26121KZI-21 handle power supply separation?

It uses three independent supply domains: VDD (digital logic), AVDD (PLL/analog core), and VDDL (clock output drivers). Each has dedicated ground pins (VSS, AVSS, VSSL) to isolate noise paths. This separation reduces supply-induced jitter and maintains <40 ps RMS cycle-to-cycle jitter even under mixed-signal PCB conditions.

Is the CY26121KZI-21 pin-compatible with other variants in the CY26121 family?

Yes - all CY26121 variants, including CY26121KZI-21, share identical 16-pin TSSOP pinout and footprint. Differences lie in internal flash configuration (output frequency mapping, spread percentage, crystal load capacitance), not physical layout or electrical interface, enabling direct substitution within the same temperature grade.