Use CDCVF2509A as a Replacement for

this Device

Designed to Meet PC SDRAM Registered

DIMM Design Support Document Rev. 1.2

Spread Spectrum Clock Compatible

Operating Frequency 25 MHz to 125 MHz

Static tPhase Error Distribution at 66MHz to

100 MHz is ±150 ps

Drop-In Replacement for TI CDC2509A With

Enhanced Performance

Jitter (cyc ? cyc) at 66 MHz to 100 MHz is

|100 ps|

Available in Plastic 24-Pin TSSOP

Phase-Lock Loop Clock Distribution for

Synchronous DRAM Applications

Distributes One Clock Input to One Bank of

Five and One Bank of Four Outputs

Separate Output Enable for Each Output

Bank

External Feedback (FBIN) Terminal Is Used

to Synchronize the Outputs to the Clock

Input

On-Chip Series Damping Resistors

No External RC Network Required

Operates at 3.3 V

description

The CDC2509C is a high-performance, low-skew, low-jitter, phase-lock loop (PLL) clock driver. It uses a PLL

to precisely align, in both frequency and phase, the feedback (FBOUT) output to the clock (CLK) input signal.

It is specifically designed for use with synchronous DRAMs. The CDC2509C operates at 3.3 V VCC. It also

provides integrated series-damping resistors that make it ideal for driving point-to-point loads.

One bank of five outputs and one bank of four outputs provide nine low-skew, low-jitter copies of CLK. Output

signal duty cycles are adjusted to 50%, independent of the duty cycle at CLK. Each bank of outputs is enabled

or disabled separately via the control (1G and 2G) inputs. When the G inputs are high, the outputs switch in

phase and frequency with CLK; when the G inputs are low, the outputs are disabled to the logic-low state.

Unlike many products containing PLLs, the CDC2509C does not require external RC networks. The loop filter

for the PLL is included on-chip, minimizing component count, board space, and cost.

Because it is based on PLL circuitry, the CDC2509C requires a stabilization time to achieve phase lock of the

feedback signal to the reference signal. This stabilization time is required, following power up and application

of a fixed-frequency, fixed-phase signal at CLK, and following any changes to the PLL reference or feedback

signals. The PLL can be bypassed for test purposes by strapping AVCC to ground.

The CDC2509C is characterized for operation from 0°C to 85°C.