Texas Instruments CDCF2509

3.3-V PHASE-LOCK LOOP CLOCK DRIVER

The CDCF2509 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 CDCF2509 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 CDCF2509 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 CDCF2509 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 CDCF2509 is characterized for operation from 0C to 85C. For application information refer to application reports High Speed Distribution Design Techniques for CDC509/516/2509/2510/2516 (literature number SLMA003) and Using CDC2509A/2510A PLL with Spread Spectrum Clocking (SSC) (literature number SCAA039).