Use CDCVF2509A as a Replacement for
this Device
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) Pin Is Used to
Synchronize the Outputs to the Clock Input
No External RC Network Required
Operates at 3.3-V VCC
Packaged in Plastic 24-Pin Thin Shrink
Small-Outline Package

description
The CDC509 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 CDC509 operates at 3.3-V VCC and is designed
to drive up to five clock loads per output.
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 percent, independent of the duty cycle at CLK. Each bank of outputs can
be 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 CDC509 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 CDC509 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, as well as following any changes to the PLL reference or
feedback signals. The PLL can be bypassed for test purposes by strapping AVCC to ground.
The CDC509 is characterized for operation from 0°C to 70°C.