Diodes Incorporated PI6C557-03AQEX

Overview

PI6C557-03AQEX from Diodes Incorporated is a PCIe 2.0-compliant spread spectrum clock generator with two HCSL differential outputs, designed for EMI reduction in PC and embedded systems. It accepts a 25 MHz crystal or clock input and generates selectable output frequencies of 25/100/125/200 MHz with programmable spread (-0.5%, -0.75%, or none) via external pins S0/S1/SS0/SS1.

For engineers reviewing the PI6C557-03AQEX datasheet, PI6C557-03AQEX pinout, PI6C557-03AQEX application, or PI6C557-03AQEX equivalent, key selection criteria include PCIe 2.0 RMS jitter (3.1 ps typ), HCSL current-mode output compliance, industrial temperature range (-40°C to +85°C), and external spread/frequency configuration logic.

Technical Context

The PI6C557-03AQEX implements a proprietary Phase-Locked Loop architecture optimized for low-jitter PCIe 2.0 timing, accepting only 25 MHz fundamental-mode crystal inputs and producing two independent HCSL differential clock pairs. Its internal current reference (IREF pin) sets output drive strength via external resistor RR (e.g., 475 Ω for 2.32 mA IREF → 6×IREF = ~13.9 mA per output).

Spread spectrum modulation operates at 30–33 kHz with down-spread options only; frequency selection is static via S0/S1 logic levels, and output enable (OE) supports tri-state control with 10 μs enable/disable timing. The device requires dual power domains (VDDA/VDDX) and separate analog/digital grounds (GNDA/GNDX) for optimal noise isolation.

Key Specifications

Pinout & Package

PI6C557-03AQEX is packaged in a 16-pin QSOP (Q16), 150 mil wide, lead-free and RoHS-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 Si53301-D-GM, the PI6C557-03AQEX delivers lower PCIe 2.0 jitter (3.1 ps vs. ≥4.5 ps), hardware-only configuration (no firmware overhead), and dedicated crystal interface - making it optimal for cost-sensitive, fixed-frequency industrial PCIe applications where simplicity and EMI margin are critical.

Availability

PI6C557-03AQEX is available at Aetrix Electronics and suitable for desktop motherboard clocking, industrial embedded controller timing, and network switch backplane synchronization requiring stable component supply and PCIe 2.0 compliance.

Supply support for PI6C557-03AQEX 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 integrated circuits, specializing in high-performance timing, power management, and signal integrity solutions.

The PI6C557 product line targets EMI-sensitive computing and communications platforms, delivering PCIe-compliant clock generation with minimal design-in effort and no software dependencies.

FAQ

What crystal specifications are required for PI6C557-03AQEX?

The device requires a 25 MHz fundamental-mode parallel-resonant crystal with ≤300 ppm frequency tolerance across temperature and specified load capacitance (e.g., 18 pF). Recommended part numbers include GC2500003 (49S/SMD, ±30 ppm) and FL2500047 (3.2×2.5 mm, ±20 ppm). External crystal capacitors must be calculated as (CL − 4) × 2 pF.

Can PI6C557-03AQEX operate without a crystal?

No - the PI6C557-03AQEX requires either a 25 MHz crystal connected between X1/CLK and X2, or a 25 MHz single-ended clock applied to X1/CLK with X2 left unconnected. It does not support arbitrary input frequencies or internal oscillators; the PLL is locked exclusively to 25 MHz.

How is HCSL output termination implemented?

HCSL outputs require external series resistors (RS = 33 Ω) and ground-return resistors (RT = 49.9 Ω) per PCI Express Layout Guidelines. The device uses open-source drivers, so termination must be placed close to the receiver. For LVDS compatibility, alternate termination (RP/RQ = 100 Ω, RT = 150 Ω) is used to achieve 1.1–1.3 V differential swing.

Does PI6C557-03AQEX support automotive qualification?

The PI6C557-03AQEX itself is not AEC-Q100 qualified. Diodes Incorporated offers automotive-grade variants (e.g., PI6C557-03AQEX-A) with PPAP capability, manufactured in IATF 16949-certified facilities. Standard PI6C557-03AQEX is rated for industrial temperature (-40°C to +85°C) and intended for non-safety-critical commercial/industrial use.