Diodes Incorporated PI6C557-05LE

Overview

PI6C557-05LE from Pericom Semiconductor is a PCIe® 2.0-compliant spread spectrum clock generator with four HCSL differential outputs, operating at 100 MHz or 200 MHz from a 25 MHz crystal input. It delivers 2.1 ps RMS phase jitter (typ), supports -0.5% to -1.5% down-spread or no spread, and functions across -40°C to +85°C industrial temperature range.

For engineers reviewing the PI6C557-05LE datasheet, PI6C557-05LE pinout, PI6C557-05LE application, or PI6C557-05LE equivalent, key selection criteria include PCIe 2.0 timing compliance, HCSL/LVDS output compatibility, spread-spectrum configuration via S[2:0] pins, and 3.3 V ±5% supply operation in embedded PC and server clocking systems.

Technical Context

This device implements a proprietary PLL architecture that synthesizes precise 100/200 MHz differential clocks from a 25 MHz fundamental-mode crystal, meeting PCI-SIG jitter requirements (≤3.1 ps RMS). Spread spectrum modulation is digitally selectable via three external pins (S2–S0) and operates at 30–33 kHz modulation frequency.

The output stage supports both HCSL (0.7 V current-mode differential pair, 6×IREF) and LVDS-compatible voltage levels, with configurable termination requiring external series (33 Ω) and ground (49.9 Ω for HCSL, 150 Ω for LVDS) resistors. Output enable (OE) and power-down (PD) pins provide system-level control with internal pull-up resistors.

Key Specifications

Pinout & Package

Package: Pb-free and Green 20-pin, 173-mil wide TSSOP (Package Code L), JEDEC MO-153F/AC compliant.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar spread spectrum clock generator applications.

Compared with IDT8T49N242B and ICS843002AGI, the PI6C557-05LE offers hardware-configured spread control, native HCSL drive strength, and lower quiescent current (120 mA vs. 160 mA), making it optimal for cost-sensitive, fixed-configuration PCIe 2.0 designs where firmware overhead must be minimized.

Availability

PI6C557-05LE is available at Aetrix Electronics and suitable for PCIe 2.0 motherboard design, server backplane timing distribution, and industrial embedded storage controller applications requiring stable component supply and full industrial temperature qualification.

Supply support for PI6C557-05LE includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Pericom Semiconductor (acquired by Diodes Incorporated in 2017) specialized in high-performance timing, interface, and signal-integrity solutions for computing, communications, and industrial markets.

The PI6C557-05LE belongs to Pericom's PCIe-compliant clock generator product line, designed specifically to replace discrete crystal oscillators and reduce EMI in high-density PC and server platforms without compromising timing accuracy.

FAQ

What crystal specifications are required for stable operation of the PI6C557-05LE?

The device requires a 25 MHz fundamental-mode parallel-resonant crystal with load capacitance of 18 pF and frequency tolerance ≤±30 ppm over -40°C to +85°C. Recommended part numbers include GC2500003 (49S/SMD), FY2500081 (5×3.2 mm), and FL2500047 (3.2×2.5 mm), all validated for low phase noise and fast startup.

Can the PI6C557-05LE operate in LVDS mode without hardware modification?

Yes - LVDS compatibility is achieved through board-level termination: replace the HCSL 33 Ω series + 49.9 Ω ground network with 100 Ω differential termination and 150 Ω pull-down on each leg. No internal register or pin change is needed; the same output drivers deliver valid LVDS voltage levels (1.0–1.325 V) under those conditions.

How does the spread spectrum selection affect output frequency accuracy?

Spread selection does not alter nominal output frequency - 100 MHz or 200 MHz remains exact. The -0.5% to -1.5% down-spread modulates the output within that center frequency, shifting instantaneous frequency by ±0.5% around 100 MHz (or 200 MHz), with modulation centered at 30–33 kHz. Frequency accuracy is preserved per crystal tolerance (±30 ppm).

What is the maximum allowable trace length for HCSL outputs driving PCIe slots?

For microstrip routing, HCSL outputs support up to 16 inches of coupled 100 Ω differential trace (L4) between the PI6C557-05LE and PCIe connector. For stripline, max length is 14.4 inches. Skew remains <50 ps across all four pairs when trace lengths are matched within ±10 mil and impedance controlled to ±10%.