5V2528

The 5V2528 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. The 5V2528 inputs, PLL core, Y0, Y1, and FBOUT buffers operate from the 3.3V VDD and AVDD power supply pins. One bank of ten outputs provide low-skew, low-jitter copies of CLK. Of the ten outputs, up to seven may be configured for 2.5V or 3.3V LVTTL outputs. The number of 2.5V outputs is controlled by 3-level input signals G_Ctrl and T_Ctrl, and by connecting the appropriate VDDQ pins to 2.5V or 3.3V. The 3-level input signals may be hard-wired to high-mid-low levels. Output signal duty cycles are adjusted to 50 percent, independent of the duty cycle at CLK. The outputs can be enabled or disabled via the G_Ctrl input. When the G_Ctrl input is mid or high, the outputs switch in phase and frequency with CLK; when the G_Ctrl is low, all outputs (except FBOUT) are disabled to the logic-low state. Unlike many products containing PLLs, the 5V2528 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 5V2528 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 AVDD to ground.