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Texas Instruments CDC421A312RGER
- Part No.:
- CDC421A312RGER
- Manufacturer:
- Texas Instruments
- Package:
- 24-VFQFN Exposed Pad
- Datasheet:
-
CDC421A312RGER.pdf
- Description:
- IC CLOCK GENERATOR 24VQFN
- Quantity:
- Payment:
- Shipping:
Inventory:1,019
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Product details
Overview
CDC421A312RGER from Texas Instruments is a fully-integrated, fixed-frequency, low-jitter crystal oscillator clock generator IC. It delivers 312.5 MHz LVPECL output from a 31.25 MHz AT-cut crystal input, features an integrated LC-based VCO (1.75–2.35 GHz), operates on single 3.3-V supply, and targets high-speed serial interface timing in telecom and datacom systems.
For engineers reviewing the CDC421A312RGER datasheet, CDC421A312RGER pinout, CDC421A312RGER application, or CDC421A312RGER equivalent, key selection criteria include its 378 fs RMS jitter (12 kHz–20 MHz), –147 dBc/Hz phase noise at 10-MHz offset, QFN-24 package thermal pad requirements, and CE-controlled LVPECL output enable functionality.
Technical Context
The CDC421A312RGER implements a PLL-based frequency synthesizer with integrated crystal oscillator circuitry and LC VCO. Its feedback divider, prescaler, and output divider are factory-configured to generate precisely 312.5 MHz from a 31.25 MHz crystal reference, eliminating external loop filter components.
It supports both crystal and LVCMOS input modes, with XIN1/XIN2 configured as differential crystal terminals or single-ended LVCMOS inputs. The chip enable (CE) pin provides full LVPECL output disable with high-impedance state, and internal power regulation ensures stable operation across –40°C to +85°C.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output frequency | 312.5 MHz - Fixed output for IEEE 802.3ae 10GBASE-R and OTU-2 line-rate applications. |
| RMS jitter (12 kHz–20 MHz) | 378 fs - Measured with 31.25 MHz crystal input; meets SONET OC-192 and 10G Ethernet jitter budgets. |
| Phase noise @ 10 MHz offset | –147 dBc/Hz - Confirmed at 312.5 MHz output; enables low BER in high-speed SerDes receivers. |
| Supply voltage | 3.3 V ±0.3 V - Single-rail operation; compatible with standard logic I/O domains and simplifies power design. |
| LVPECL output swing | 407–1076 mV differential - Ensures robust signal integrity into 50-Ω terminated transmission lines. |
| Operating temperature | –40°C to +85°C - Industrial-grade rating suitable for uncooled telecom line cards and embedded networking hardware. |
| Package | QFN-24 (4 mm × 4 mm, 1 mm max height) - Exposed thermal pad requires PCB soldering for thermal management and EMI control. |
Pinout & Package
Package: VQFN-24 (RGE), 4 mm × 4 mm body, 1 mm maximum height, exposed thermal pad (pin 25) requiring solder connection to PCB ground plane for thermal and electrical performance.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VCC (pins 16, 17) | Power supply input | 3.3-V core and I/O rail; decoupling capacitors required within 3 mm of each pin per layout guidelines. |
| GND (pins 8, 9) | Ground reference | Dual ground pins minimize ground bounce; connect directly to solid ground plane under package. |
| XIN1 (pin 21) | Clock input (crystal or LVCMOS) | In crystal mode: connects to one crystal terminal; in LVCMOS mode: primary reference input. |
| XIN2 (pin 22) | Clock input (crystal or LVCMOS) | In crystal mode: connects to second crystal terminal; in LVCMOS mode: tie to GND. |
| CE (pin 1) | Chip enable control | LVCMOS-compatible active-high signal; drives outputs to Hi-Z when low, enabling power-gating. |
| OUTP (pin 10) | LVPECL positive output | Differential output pair; requires 50-Ω termination to VCC–2 V and AC-coupling for DC blocking. |
| OUTN (pin 7) | LVPECL negative output | Complementary output to OUTP; forms 312.5 MHz differential clock signal with <230 ps rise/fall times. |
| NC (pins 2–6, 11–15, 18–20, 23, 24) | No-connect | TI test pins; must remain unconnected and floating per datasheet guidance. |
Key Features
| Feature | Design Value |
|---|---|
| Fully integrated crystal oscillator + PLL + VCO | Eliminates external crystal load capacitors, loop filter components, and discrete VCO tuning elements. |
| Low-phase-noise LC VCO (1.75–2.35 GHz) | Enables clean multiplication without added jitter from varactor-based or ring oscillators. |
| 378 fs RMS jitter (12 kHz–20 MHz) | Meets stringent jitter requirements for 10G Ethernet PHYs and OTN framers without post-synthesis cleanup. |
| LVPECL outputs with 230-ps edge rates | Supports direct interfacing to high-speed SerDes CDR circuits and FPGA transceivers with minimal signal conditioning. |
| Chip enable with Hi-Z output state | Allows dynamic clock gating in multi-rail systems without signal contention or termination mismatch issues. |
Applications
| 10GBASE-R Ethernet PHY Timing | OTU-2 Optical Transport Network |
|---|---|
|
Use Scenario: Generating the precise 312.5 MHz reference clock for 10GBASE-R PCS/PMA layers in switch/router line cards. IC Role / Device Role / Timing Role: Primary clock source feeding the gearbox and serializer stages; replaces discrete crystal + PLL solutions. Use Value: 378 fs jitter ensures compliance with IEEE 802.3ae jitter tolerance masks and reduces bit error rate in backplane links. |
Use Scenario: Providing the frame-aligned 312.5 MHz clock for OTU-2 (10.709 Gbps) framer and mapper ASICs in DWDM line systems. IC Role / Device Role / Timing Role: System-level timing reference synchronized to line rate; used in conjunction with elastic buffers. Use Value: –147 dBc/Hz phase noise at 10-MHz offset minimizes wander accumulation across cascaded OEO regenerators. |
| Synchronous Ethernet (SyncE) Distribution | High-Speed ADC/DAC Sampling Clock |
|
Use Scenario: Delivering traceable, low-jitter 312.5 MHz clocks to multiple SyncE-compliant PHYs in mobile backhaul baseband units. IC Role / Device Role / Timing Role: Stratum-3-equivalent clock generator with holdover stability enabled by crystal reference. Use Value: Integrated crystal oscillator eliminates external crystal layout sensitivity and improves phase transient response during network sync loss. |
Use Scenario: Supplying sampling clock to 12-bit+ ADCs/DACs operating at 312.5 MSPS in software-defined radio and test equipment. IC Role / Device Role / Timing Role: Low-phase-noise clock source for Nyquist-rate sampling; reduces aperture jitter-induced SNR degradation. Use Value: 378 fs RMS jitter translates to >72 dB theoretical SNR ceiling at 312.5 MSPS, preserving dynamic range. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar clock generator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LMK03806RHAR | Programmable output (10–900 MHz), higher power (450 mW), requires external loop filter and crystal. | Supports multi-rate systems; less suitable for fixed 312.5 MHz where simplicity and jitter are critical. | Choose when flexibility across multiple line rates is required; avoid if lowest jitter and BOM count are top priorities. |
| CDCM6208V2RGZR | 8-output, programmable jitter cleaner (100 fs typical), supports crystal or LVDS input, larger QFN-48 package. | Targets multi-clock domain systems; over-specified for single-output 312.5 MHz use cases. | Prefer when consolidating multiple clock domains onto one device; not cost-optimized for dedicated 312.5 MHz generation. |
Compared with LMK03806RHAR and CDCM6208V2RGZR, the CDC421A312RGER offers lower jitter (378 fs vs ≥500 fs), smaller footprint (QFN-24 vs QFN-48), and zero external passive components-making it optimal for space-constrained, fixed-frequency 10G timing applications.
Availability
CDC421A312RGER is available at Aetrix Electronics and suitable for telecom infrastructure, optical transport equipment, and high-speed data acquisition systems requiring stable component supply and guaranteed long-term availability.
Supply support for CDC421A312RGER 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
Texas Instruments is a global semiconductor leader specializing in analog, embedded processing, and connectivity technologies with over 50 years of innovation in precision timing and signal chain solutions.
The CDC421Axxx family was designed specifically for low-jitter, fixed-frequency clock generation in high-speed serial interfaces-including 10G Ethernet, OTN, and CPRI-where integration, phase noise, and reliability are critical.
FAQ
What crystal frequency is required for CDC421A312RGER to generate 312.5 MHz?
The CDC421A312RGER requires a 31.25 MHz AT-cut fundamental-mode crystal connected between XIN1 and XIN2. This 10× multiplication ratio is factory-trimmed and non-programmable; using any other crystal frequency will not yield the specified 312.5 MHz output.
Does CDC421A312RGER support LVCMOS input instead of a crystal?
Yes, CDC421A312RGER supports LVCMOS input mode: drive XIN1 with a 31.25 MHz LVCMOS signal and tie XIN2 to GND. Input thresholds are 0.3×VCC (low) and 0.7×VCC (high); the device maintains identical 312.5 MHz output and jitter performance in this mode.
What is the recommended PCB layout for the thermal pad on CDC421A312RGER?
The exposed thermal pad (pin 25) must be soldered to a solid copper ground plane using ≥78% solder paste coverage. TI recommends 20–24 thermal vias (0.25 mm diameter, 0.6 mm pitch) filled or tented, placed within the pad area to ensure mechanical reliability and thermal resistance <10°C/W.
How does the CE pin affect power consumption and output state in CDC421A312RGER?
When CE = 0, CDC421A312RGER disables all internal current sources: OUTP and OUTN enter high-impedance state, and total supply current drops to <10 µA. When CE = 1, full operation resumes with 110 mA typical ICC, enabling dynamic power gating in burst-mode systems.
Is CDC421A312RGER compliant with RoHS and lead-free assembly standards?
Yes, CDC421A312RGER is RoHS-compliant and uses NiPdAu (NIPDAU) lead finish. It carries MSL Level-2 (260°C peak reflow, 1-year floor life) and is qualified for lead-free reflow per JEDEC J-STD-020. Full compliance documentation is available via TI's Quality & Environmental page.
CDC421A312RGER Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- -
- Package/Case:
- 24-VFQFN Exposed Pad
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Programmable:
- Not Verified
- Type:
- Clock Generator
- PLL:
- Yes
- Input:
- LVCMOS, Crystal
- Output:
- LVPECL
- Number of Circuits:
- 1
- Ratio - Input:Output:
- 1:1
- Differential - Input:Output:
- No/Yes
- Frequency - Max:
- 312.5MHz
- Divider/Multiplier:
- Yes/No
- Voltage - Supply:
- 3V ~ 3.6V
- Operating Temperature:
- -40°C ~ 85°C
- Mounting Type:
- Surface Mount
- Grade:
- -
- Qualification:
- -
- Supplier Device Package:
- 24-VQFN (4x4)
CDC421A312RGER FAQ
1.How can I place an order for CDC421A312RGER through Aetrix?
Please submit a Request for Quotation (RFQ) for CDC421A312RGER 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 CDC421A312RGER reliable?
The price and inventory of CDC421A312RGER are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for CDC421A312RGER is usually 5 days.
3.What payment methods are accepted for CDC421A312RGER?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for CDC421A312RGER transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for CDC421A312RGER?
CDC421A312RGER orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your CDC421A312RGER 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 CDC421A312RGER?
For technical support, including CDC421A312RGER datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your CDC421A312RGER requirements.
6.How does Aetrix verify that CDC421A312RGER is sourced from the original manufacturer or authorized distributors?
All CDC421A312RGER 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 CDC421A312RGER meets industry standards.
7.What is the process for return or replacement of CDC421A312RGER?
All CDC421A312RGER units undergo pre-shipment inspection (PSI). If there is an issue with CDC421A312RGER, 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 CDC421A312RGER part is unused and in its original packaging.
Return procedure for CDC421A312RGER:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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