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Infineon Technologies CY26121ZI-21
- Part No.:
- CY26121ZI-21
- Manufacturer:
- Infineon Technologies
- Package:
- 16-TSSOP (0.173", 4.40mm Width)
- Datasheet:
-
CY26121ZI-21.pdf
- Description:
- IC FANOUT DIST 16TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:4,491
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Product details
Overview
CY26121ZI-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, targeting EMI reduction in industrial-grade embedded systems including graphics controllers and PCI Express clock trees.
For engineers reviewing the CY26121ZI-21 datasheet, CY26121ZI-21 pinout, CY26121ZI-21 application, or CY26121ZI-21 equivalent, key selection criteria include industrial temperature support (–40°C to +85°C), TSSOP-16 package compatibility, dual-output frequency selection via CLKSEL, and verified 15-pF crystal load capacitance for noise-sensitive timing domains.
Technical Context
The CY26121ZI-21 implements a flash-configurable PLL with spread-spectrum modulation logic that dynamically shifts output frequency around nominal values to reduce electromagnetic interference peaks. Its dual-output architecture supports independent clock distribution paths (CLKA–CLKD) referenced to VDDL, with analog and digital supply separation (AVDD/VDD/VDDL) ensuring low-noise timing synthesis.
Frequency selection is controlled by the CLKSEL pin: logic 0 selects 33.33 MHz, logic 1 selects 25.00 MHz. The device uses a parallel-resonant fundamental-mode crystal (15 pF load) on XIN/XOUT, and includes weak internal pull-ups on CLKSEL and SSON pins for default SS-enable behavior without external biasing.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Frequency | 25 MHz crystal or CMOS reference - matches standard low-cost quartz resonators and eliminates need for external oscillator. |
| Output Frequencies | 33.33 MHz or 25.00 MHz selectable via CLKSEL pin - enables single-part support for multiple system clock domains. |
| Spread Spectrum | –2.8% downspread at 30 kHz nominal modulation - reduces peak radiated emissions by spreading energy across ~100 kHz bandwidth. |
| RMS Cycle-to-Cycle Jitter | 15–40 ps with spread spectrum enabled - meets PCI Express Gen1/Gen2 and USB 2.0 clock jitter requirements. |
| Supply Voltage | 3.135–3.465 V for VDD, AVDD, and VDDL - ensures stable operation across industrial voltage tolerances and board-level ripple. |
| Operating Temperature | –40°C to +85°C - qualified for industrial environments including factory automation and network infrastructure equipment. |
| Crystal Load Capacitance | 15 pF - requires matching 15-pF parallel-resonant crystal; avoids tuning errors and startup failures in high-reliability designs. |
Pinout & Package
Package: 16-pin Thin Shrink Small Outline Package (TSSOP), 4.4 mm body width, lead pitch 0.65 mm, RoHS-compliant.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| XIN (Pin 1) | Reference Input / Crystal Terminal | Accepts 25-MHz fundamental-mode crystal or CMOS clock; internal oscillator circuitry drives crystal directly. |
| VDD (Pin 2) | Digital Core Supply | 3.3-V supply for logic block, configuration memory, and control circuitry; decoupling required near pin. |
| AVDD (Pin 3) | Analog PLL Supply | Independent 3.3-V rail for PLL charge pump and VCO; isolation from digital noise improves jitter performance. |
| CLKSEL (Pin 4) | Output Frequency Select | Logic level selects 33.33 MHz (0) or 25.00 MHz (1); internal weak pull-up defaults to 25-MHz mode if left floating. |
| AVSS (Pin 5) | Analog Ground | Return path for AVDD; must be routed separately from digital ground to minimize PLL phase noise coupling. |
| VSSL (Pin 6) | CLK Output Ground | Dedicated ground for clock buffer outputs (CLKA–CLKD); reduces switching noise on timing signals. |
| CLKA–CLKD (Pins 7,8,9,12) | CMOS Clock Outputs | Four identical 3.3-V CMOS outputs referenced to VDDL; each capable of driving 15-pF load at ≤40 ps jitter. |
| SSON (Pin 10) | Spread Spectrum Enable | Active-high control: logic 1 enables modulation; internal weak pull-up ensures SS active on power-up unless pulled low. |
| VDDL (Pin 11) | Output Driver Supply | 3.3-V supply for clock buffers only; separate from VDD/AVDD to isolate output switching transients from core logic. |
| VSS (Pin 13) | Digital Ground | Main digital return; connects to system GND plane but must be star-connected to avoid ground bounce on CLK outputs. |
| REF (Pin 14) | Reference Output | Buffers XIN signal at VDD level; usable as clean 25-MHz source for other ICs without loading crystal node. |
| NC (Pin 15) | No Connect | Not internally bonded; must remain unconnected to prevent parasitic coupling or latch-up risk. |
| XOUT (Pin 16) | Crystal Output | Completes crystal oscillator loop; must float when XIN is driven externally to avoid contention. |
Key Features
| Feature | Design Value |
|---|---|
| Flash-programmable PLL | Enables one-time configuration of spread-spectrum parameters and output frequencies without external EEPROM or I²C interface. |
| Separate analog/digital supplies | Reduces supply-induced jitter by isolating PLL VCO and charge pump from digital switching noise on VDD and VSSL. |
| Four synchronized CMOS outputs | Delivers matched skew and identical edge rates (0.8–1.4 V/ns) across CLKA–CLKD, simplifying multi-clock domain synchronization. |
| 15-pF crystal load optimization | Guarantees reliable start-up and frequency stability with industry-standard 15-pF parallel-resonant crystals, eliminating tuning iterations. |
| Industrial temperature qualification | Validated operation from –40°C to +85°C ensures timing integrity in extended-temperature applications like motor drives and base stations. |
Applications
| PCI Express Root Complex Clocking | Embedded Graphics Controller Timing |
|---|---|
|
Use Scenario: Provides primary 25-MHz or 33.33-MHz reference clock to PCIe root complex PHY and associated SerDes logic in industrial PCs. IC Role / Device Role / Timing Role: Spread-spectrum clock generator delivering low-jitter, EMI-compliant reference to meet PCIe Gen1/Gen2 specification limits. Use Value: Reduces radiated emissions from PCIe slot interfaces by >10 dB at fundamental harmonics, easing FCC Class B compliance testing. |
Use Scenario: Supplies synchronized clocks to GPU memory interface, display controller, and video encoder in medical imaging systems. IC Role / Device Role / Timing Role: Dual-frequency clock source enabling dynamic clock scaling between high-resolution capture (33.33 MHz) and low-power display (25 MHz). Use Value: Eliminates need for two discrete oscillators while maintaining <40 ps cycle-to-cycle jitter required for DDR2/DDR3 memory timing margins. |
| Factory Automation PLC Backplane | Network Switch Fabric Timing |
|
Use Scenario: Generates timing for real-time I/O modules and fieldbus communication controllers in programmable logic controllers operating in harsh industrial environments. IC Role / Device Role / Timing Role: Industrial-grade clock generator with –40°C to +85°C operation and robust crystal drive capability. Use Value: Ensures deterministic timing across distributed I/O nodes despite wide ambient temperature swings and electrical noise on DIN-rail power rails. |
Use Scenario: Distributes low-jitter clocks to packet buffering ASICs, MAC controllers, and SERDES transceivers in 1/10-GbE switch fabric boards. IC Role / Device Role / Timing Role: Multi-output clock source supporting simultaneous 25-MHz management interface and 33.33-MHz data-path timing. Use Value: Minimizes bit error rate (BER) in high-speed serial links by maintaining sub-50-ps RMS jitter under spread-spectrum operation. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar spread-spectrum clock generator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| IDT 8T49N241 | Supports up to 4 LVDS/LVPECL outputs; requires external configuration EEPROM; higher power (85 mA typical). | Targets telecom infrastructure with differential signaling; lacks integrated crystal driver. | Choose for systems requiring differential outputs or multi-protocol clock synthesis beyond spread-spectrum only. |
| Si5351A | Programmable I²C-based clock generator; no integrated spread-spectrum; 3.3-V CMOS outputs; 100-fs phase jitter (non-SS). | Used in software-defined radio and FPGA prototyping where flexible frequency synthesis outweighs EMI reduction needs. | Prefer when design requires dynamic frequency reconfiguration or ultra-low phase jitter without spread-spectrum trade-offs. |
Compared with IDT 8T49N241 and Si5351A, the CY26121ZI-21 offers lower system cost through integrated crystal drive, flash configuration, and industrial temperature support - making it optimal for fixed-frequency, EMI-critical embedded applications without I²C or differential signaling requirements.
Availability
CY26121ZI-21 is available at Aetrix Electronics and suitable for industrial automation controllers, network infrastructure equipment, and embedded graphics subsystems requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for CY26121ZI-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) is a fabless semiconductor company specializing in programmable system-on-chip solutions, timing devices, and USB/USB-C controllers for industrial, automotive, and consumer markets.
The PacketClock™ family was designed specifically for EMI reduction in high-speed digital systems using spread-spectrum clocking, with emphasis on plug-and-play integration, industrial reliability, and minimal external components.
FAQ
What is the function of the REF pin on CY26121ZI-21?
The REF pin (Pin 14) provides a buffered, non-inverted copy of the XIN input signal at VDD level. It is intended to drive secondary clock loads without loading the crystal node, preserving oscillator stability. REF operates at full CMOS levels and can source/sink ≥12 mA, making it suitable for feeding auxiliary timing circuits or test points.
Can CY26121ZI-21 operate with a 12.5-MHz input?
No. The CY26121ZI-21 is specified exclusively for 25-MHz reference input, either from a crystal (XIN/XOUT) or external CMOS source (XIN only). Its PLL architecture and internal dividers are hardwired for 25-MHz base frequency; using 12.5 MHz will result in incorrect output frequencies and potential failure to lock.
How does CLKSEL behavior differ between CY26121ZI-21 and CY26121ZI-3?
On CY26121ZI-21, CLKSEL = 0 selects 33.33 MHz and CLKSEL = 1 selects 25.00 MHz. In contrast, CY26121ZI-3 uses CLKSEL = 0 for 66.66 MHz and CLKSEL = 1 for 33.33 MHz. This functional difference is fixed per part number and cannot be reconfigured - selecting the correct variant is essential for target frequency alignment.
Is external termination required on CLKA–CLKD outputs?
No external series termination is required for CLKA–CLKD outputs when driving standard CMOS loads ≤15 pF. The outputs are designed as push-pull CMOS drivers with 12–24 mA drive strength and controlled edge rates (0.8–1.4 V/ns). Series resistors may be added only if board trace impedance exceeds 50 Ω or if overshoot/ringing is observed in specific layout conditions.
CY26121ZI-21 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Infineon Technologies
- Series:
- PacketClock™
- Package/Case:
- 16-TSSOP (0.173", 4.40mm Width)
- Packaging:
- Tube
- Product Status:
- Obsolete
- Programmable:
- Not Verified
- Type:
- Fanout Distribution, Multiplexer, Spread Spectrum Clock Generator
- PLL:
- Yes with Bypass
- Input:
- Clock, Crystal
- Output:
- Clock
- Number of Circuits:
- 1
- Ratio - Input:Output:
- 1:5
- Differential - Input:Output:
- No/No
- Frequency - Max:
- 33.33MHz
- Divider/Multiplier:
- Yes/No
- Voltage - Supply:
- 3.135V ~ 3.465V
- Operating Temperature:
- -40°C ~ 85°C
- Mounting Type:
- Surface Mount
- Grade:
- -
- Qualification:
- -
- Supplier Device Package:
- 16-TSSOP
CY26121ZI-21 FAQ
1.How can I place an order for CY26121ZI-21 through Aetrix?
Please submit a Request for Quotation (RFQ) for CY26121ZI-21 on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.
2.Are the price and stock information for CY26121ZI-21 reliable?
The price and inventory of CY26121ZI-21 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for CY26121ZI-21 is usually 5 days.
3.What payment methods are accepted for CY26121ZI-21?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for CY26121ZI-21 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for CY26121ZI-21?
CY26121ZI-21 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your CY26121ZI-21 order is processed, you will receive an email with the shipment details and tracking number.
Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.
5.How can I obtain technical support or documentation for CY26121ZI-21?
For technical support, including CY26121ZI-21 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your CY26121ZI-21 requirements.
6.How does Aetrix verify that CY26121ZI-21 is sourced from the original manufacturer or authorized distributors?
All CY26121ZI-21 products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that CY26121ZI-21 meets industry standards.
7.What is the process for return or replacement of CY26121ZI-21?
All CY26121ZI-21 units undergo pre-shipment inspection (PSI). If there is an issue with CY26121ZI-21, returns or replacements are accepted under the following conditions:
1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.
2.The issue is reported within 90 days of delivery.
3.The CY26121ZI-21 part is unused and in its original packaging.
Return procedure for CY26121ZI-21:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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