PI6C557-03LE

Overview

The PI6C557-03LE is a spread spectrum clock generator designed for PCI Express and Ethernet applications. It accepts a 25 MHz crystal or CMOS input and generates two differential outputs in HCSL or LVDS formats. The device operates on a 3V to 3.6V supply with a maximum output frequency of 200 MHz. Key electrical parameters include a typical cycle-to-cycle jitter of 60 ps, an operating temperature range of -40°C to +85°C, and a package type of 16-TSSOP.

Feature Summary

• Supports spread spectrum frequencies of ±0.25%, -0.5%, -0.75%, and no spread via pin selection
• Provides selectable output frequencies of 25 MHz, 100 MHz, 125 MHz, and 200 MHz
• Features low cycle-to-cycle jitter (typical 60 ps) to reduce electromagnetic interference
• Configurable for both HCSL and LVDS compatible output voltage levels

Applications

• PCI Express Gen 1 and Gen 2 clock generation
• Ethernet system clock distribution
• PC and embedded systems requiring EMI reduction

Procurement Notes

Verify the ordering suffix 'E' confirms lead-free and green packaging compliance. Confirm the absence of the 'X' suffix indicates tube packaging rather than tape and reel. Ensure the specific revision matches the required PCB footprint and thermal characteristics for the 16-TSSOP package.

Selection Notes

Select this component when a single-ended 25 MHz input is available and differential HCSL or LVDS outputs are required. Verify that the application supports the configurable spread spectrum options and does not require higher frequencies beyond 200 MHz. Check if the industrial temperature range meets the environmental requirements.

Part Context

This part belongs to the PI6C557 series of PCI Express clock generators manufactured by Diodes Incorporated (formerly Pericom). The 'LE' suffix specifically denotes the lead-free and green packaging variant housed in a standard 16-pin TSSOP package.

Replacement Considerations

For PCIe Gen 2 applications, consider the 5V41065. For PCIe Gen 3 applications, consider the 5V41235. Direct functional replacements within the same family should be verified against pinout and output configuration compatibility.

FAQ

How is the output frequency selected?

The output frequency is configured using pins S0 and S1. Setting S1=0, S0=0 yields 25 MHz; S1=0, S0=1 yields 100 MHz; S1=1, S0=0 yields 125 MHz; and S1=1, S0=1 yields 200 MHz.

What is the function of the IREF pin?

The IREF pin connects to a precision external resistor (RR) that sets the internal current reference. For a target trace impedance of 50Ω, a 475Ω resistor provides an IREF of 2.32 mA.

How is spread spectrum modulation controlled?

Spread spectrum is selected via pins SS0 and SS1. Options include Center ±0.25% (SS1=0, SS0=0), Down -0.5% (SS1=0, SS0=1), Down -0.75% (SS1=1, SS0=0), and No Spread (SS1=1, SS0=1).