CY2SSTV855ZXC

Overview

The CY2SSTV855ZXC is a high-performance, very-low-skew, zero-delay differential clock buffer and driver manufactured by Skyworks Solutions Inc. It distributes a differential SSTL_2 clock input to four differential output pairs and one feedback pair using an internal phase-locked loop (PLL). The device operates with AVDD and VDDQ supplies at 2.5V nominal. Key specifications include a low-to-high propagation delay of 1.5 ns typical, output skew under 100 ps, and half-period jitter below 100 ps for frequencies above 66 MHz. It supports Spread Spectrum Clocking (SSCG) for EMI reduction and conforms to JEDEC DDR specifications.

Feature Summary

• Zero-delay buffer architecture utilizing external feedback pins (FBINT, FBINC) connected to feedback outputs (FBOUTT, FBOUTC) to eliminate propagation delay.
• Supports Spread Aware™ technology to track spread spectrum clock inputs, reducing electromagnetic interference (EMI).
• Provides five differential output pairs: four clock outputs (YT/YC) and one feedback pair, all compatible with SSTL_2 standards.
• Features a power-down control pin (PWRDWN) that disables outputs to a high-impedance state and shuts down the PLL when asserted LOW.

Applications

• Double Data Rate Synchronous DRAM (DDR) clock distribution networks.
• Nested clock tree applications requiring near-zero delay between reference and output clocks.
• Systems requiring low-jitter differential clock buffering with EMI mitigation capabilities.

Procurement Notes

Verify the ordering suffix 'ZXC' corresponds to the commercial temperature range (0°C to 70°C) in the 28-pin TSSOP package. Confirm whether tape and reel packaging is required by checking for the 'CT' suffix variant. Ensure compatibility with the 2.5V supply voltage requirements specified in the datasheet.

Selection Notes

Select this component for designs requiring a 1:5 differential clock split with minimal skew. Ensure the PCB layout allows for close placement of bypass capacitors (< 0.2”) to power pins to maintain high-frequency filtering characteristics. Verify that the input clock frequency falls within the operational range where static phase offset remains within ±450 ps.

Part Context

This part belongs to the CY2SSTV855 family of differential clock buffers. The 'ZXC' suffix indicates a lead-free version in a standard commercial temperature grade. Other variants include industrial grades ('ZI') and tape-and-reel options ('CT'). The device is functionally equivalent to other members of the series but differs in temperature rating and packaging format.

Replacement Considerations

Direct replacements within the same family include CY2SSTV855ZC (commercial, standard pkg), CY2SSTV855ZCT (commercial, tape & reel), CY2SSTV855ZI (industrial), and CY2SSTV855ZXI (industrial, lead-free). Ensure the substitute matches the required operating temperature range and packaging type.

FAQ

How does the CY2SSTV855 achieve zero-delay buffering?

It achieves near-zero delay by connecting the external feedback inputs (FBINT/FBINC) to the feedback outputs (FBOUTT/FBOUTC). The PLL aligns the output edge with the input reference edge, effectively eliminating propagation delay through the device.

What is the effect of the PWRDWN pin on the device operation?

When PWRDWN is HIGH, the device operates normally. When PWRDWN is LOW, all outputs are disabled to a high-impedance state, and the PLL is shut down.

Does the CY2SSTV855 support spread spectrum clocking?

Yes, the device is Spread Aware and supports tracking of spread spectrum clock inputs to reduce electromagnetic interference (EMI).