Texas Instruments CDCF2509PW

Overview

CDCF2509PW from Texas Instruments is a 3.3 V, PLL-based clock distribution IC designed for PC133 SDRAM Registered DIMM applications. It distributes one clock input to nine low-skew outputs (5+4 banks), delivers ±125 ps static phase error at 66–133 MHz, achieves |70| ps cycle-to-cycle jitter, and integrates on-chip 25-Ω series-damping resistors for point-to-point SDRAM clock tree driving.

For engineers reviewing the CDCF2509PW datasheet, CDCF2509PW pinout, CDCF2509PW application, or CDCF2509PW equivalent, key selection criteria include its 24-pin TSSOP package, bank-selectable output enables (1G/2G), external feedback loop via FBIN/FBOUT, spread-spectrum compatibility, and guaranteed operation from 0°C to 85°C without external RC components.

Technical Context

The CDCF2509PW implements a fully integrated PLL architecture with on-chip loop filter, eliminating external RC networks. Its feedback path requires direct FBOUT-to-FBIN connection to synchronize outputs to CLK with zero nominal phase error.

It features two independent output banks - 1Y0–1Y4 (pins 3,4,5,8,9) and 2Y0–2Y3 (pins 21,20,17,16) - each controlled by dedicated enable inputs (1G, 2G). Output duty cycles are actively adjusted to 50%, independent of CLK duty cycle, and all outputs include integrated 25-Ω series-damping resistors.

Key Specifications

Pinout & Package

Package: 24-pin TSSOP (PW), 0.65 mm pitch, 7.8 mm × 4.4 mm footprint, 1.2 mm max height, RoHS-compliant, moisture sensitivity level 1.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar PLL clock distribution applications.

Compared with CDCF2509PW, CDCF2509PWR offers identical functionality in tape-and-reel format for SMT lines, while CDCVF2509A provides superior jitter and temperature range but requires PCB redesign due to 28-pin TSSOP packaging and altered pin assignment.

Availability

CDCF2509PW is available at Aetrix Electronics and suitable for PC133 SDRAM modules, industrial memory subsystems, and legacy server board repairs requiring stable component supply with full traceability and long-term lifecycle support.

Supply support for CDCF2509PW 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 logic technologies, with decades of expertise in clock management and memory interface solutions.

The CDCF2509PW belongs to TI's legacy clock distribution product line, engineered specifically for PC133 SDRAM Registered DIMM timing compliance and high-reliability synchronous DRAM clock tree implementation.

FAQ

What is the recommended power-up sequence for CDCF2509PW?

The CDCF2509PW requires no specific power sequencing between VCC and AVCC, but both must be stable before applying CLK. A 1 ms stabilization delay after CLK application is mandatory for PLL lock. AVCC may be strapped to ground only during test to bypass the PLL; normal operation requires AVCC = VCC = 3.3 V. This ensures proper CDCF2509PW phase alignment and jitter performance.

Can CDCF2509PW drive unbuffered SDRAM modules?

No - CDCF2509PW is explicitly designed for Registered DIMMs per PC133 specification Rev. 0.9, which require clock registration. Its output drive strength, skew, and phase characteristics are optimized for loading registered clock buffers, not direct SDRAM clock inputs. Using CDCF2509PW with unbuffered modules risks timing violations and is outside its validated application scope.

Does CDCF2509PW support differential clock inputs?

No - CDCF2509PW accepts only single-ended CMOS/TTL-compatible clock inputs on the CLK pin (24). It does not include internal termination, LVDS receivers, or differential input circuitry. External conversion to single-ended is required if sourcing from differential oscillators or clock generators.

How is the feedback loop implemented for CDCF2509PW?

The CDCF2509PW feedback loop is completed by hard-wiring FBOUT (pin 12) directly to FBIN (pin 13) with minimal trace length (<5 mm recommended). This closed loop allows the internal PLL to synchronize FBOUT phase to CLK, achieving zero nominal phase error. No external components are needed - the loop filter is fully integrated.

Is CDCF2509PW still in active production?

CDCF2509PW is marked NRND (Not Recommended for New Designs) by Texas Instruments, indicating it remains in production for legacy support but is superseded by CDCVF2509A. Aetrix Electronics maintains inventory and offers full traceability, making CDCF2509PW suitable for repair, maintenance, and continuity of existing PC133-based systems.