Diodes Incorporated PI6C557-05BLEX

Overview

PI6C557-05BLEX from Diodes Incorporated is a PCIe® 3.0-compliant spread spectrum clock generator with four HCSL differential outputs, 100/200 MHz selectable frequencies, 0.48 ps RMS high-frequency jitter (typ), and -0.5% to -1.5% down-spread modulation. It accepts a 25 MHz crystal input and operates across -40°C to +85°C for EMI reduction in PC and embedded host systems.

For engineers reviewing the PI6C557-05BLEX datasheet, PI6C557-05BLEX pinout, PI6C557-05BLEX application, or PI6C557-05BLEX equivalent, key selection criteria include PCIe 3.0 phase jitter compliance, HCSL/LVDS output compatibility, spread-spectrum selectability via S[2:0], 3.3 V ±5% supply operation, and TSSOP-20 packaging for space-constrained board layouts.

Technical Context

The PI6C557-05BLEX employs a proprietary PLL architecture optimized for PCIe 3.0 jitter performance, with low-bandwidth (2–5 MHz) and high-bandwidth (0.47–0.48 ps RMS) filtering to meet PCI-SIG specification requirements. It supports dual-frequency operation (100 MHz and 200 MHz) determined by S[2:0] configuration and delivers differential outputs using current-mode HCSL drivers.

Spread spectrum modulation is digitally selected via three external pins (S0–S2), enabling discrete -0.5%, -1.0%, -1.5%, or no-spread modes without requiring external components. Output enable (OE) and power-down (PD) pins provide system-level control over clock distribution and power gating.

Key Specifications

Pinout & Package

Package: 20-pin TSSOP (173 mil wide), RoHS-compliant, lead-free, green (halogen/antimony-free).

Key Features

Applications

Equivalent & Alternatives

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

Compared with IDT8T49N242BGI and Si53320-D-GM, the PI6C557-05BLEX offers lower-cost, pin-strapped simplicity for fixed-frequency PCIe 3.0 clocking, with native HCSL drive eliminating level-shifters and reducing BOM count by two components per channel.

Availability

PI6C557-05BLEX is available at Aetrix Electronics and suitable for desktop motherboard clocking, server PCIe expansion slot timing, and embedded industrial controller designs requiring stable component supply and long-term lifecycle support.

Supply support for PI6C557-05BLEX 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

Diodes Incorporated is a global manufacturer of discrete semiconductors and analog ICs, specializing in power management, signal integrity, and timing solutions for industrial, computing, and communications markets.

The PI6C557-05BLEX belongs to Diodes' Pericom-branded clock generation portfolio, designed specifically for EMI reduction in PCIe 3.0-compliant host systems through hardware-configurable spread spectrum and HCSL-native output drivers.

FAQ

What crystal specifications are required for stable operation?

The PI6C557-05BLEX requires a 25 MHz fundamental-mode parallel-resonant crystal with ≤30 ppm frequency tolerance across -40°C to +85°C, 18 pF load capacitance, and low ESR (e.g., GC2500003 or FL2500047). External load capacitors are not needed due to internal driver optimization.

How is HCSL output current set and verified?

HCSL output current is set by connecting a precision 475 Ω resistor between IREF (Pin 10) and GND, establishing a 2.32 mA reference that scales to 6×IREF = 13.9 mA per output leg. This matches PCIe HCSL specification (±10%) and is verified using differential probe measurements at the output pins.

Can the device operate in LVDS mode, and what layout changes are needed?

Yes - the PI6C557-05BLEX supports LVDS-compatible voltage levels by configuring external termination: 100 Ω differential load (RP/RQ = 100 Ω) and 150 Ω ground return (RT). Layout must use controlled 100 Ω differential microstrip/stripline routing with <500 ps rise/fall times and strict length matching (<50 ps skew).

What is the power-up sequence requirement for reliable initialization?

No strict power sequencing is required. The device stabilizes within 3.0 ms after VDDXD reaches 3.3 V. Crystal oscillation starts automatically; PLL lock occurs within 10 ms. OE and PD pins default to enabled (high) via internal pull-ups, so outputs activate immediately after lock unless externally asserted low.