Microchip Technology SY75578LMG

Overview

SY75578LMG from Micrel is a PCIe-compliant 1:8 differential clock fanout buffer with HCSL/LVDS dual-input multiplexer, 267MHz max frequency, 130fsrms phase jitter at 200MHz, <100ps output-to-output skew, and 3.3V ±5% supply operation-designed for high-speed server and storage interconnect timing distribution.

For engineers reviewing the SY75578LMG datasheet, SY75578LMG pinout, SY75578LMG application, or SY75578LMG equivalent, key selection criteria include HCSL output compatibility with PCIe Gen1–Gen3 reference clocks, industrial-temperature operation (−40°C to +85°C), QFN-32 package thermal performance, and input MUX control via TTL/CMOS SEL pin.

Technical Context

The SY75578LMG implements a fully differential signal path with two independent HCSL/LVDS input pairs (IN0/IN1) selected by a single-ended TTL/CMOS SEL pin, enabling dynamic source switching without external logic. Its internal current-mode driver architecture supports precise 50Ω output impedance matching and maintains sub-100ps skew across all eight HCSL output pairs (Q0–Q7).

Phase jitter is minimized via low-noise biasing and optimized layout in the 32-pin QFN package, achieving 130fsrms (12kHz–20MHz integration) at 200MHz-meeting PCIe Gen3 jitter budget requirements. Power management includes asynchronous OE and /PD pins for output tri-state and full chip shutdown, respectively.

Key Specifications

Pinout & Package

SY75578LMG is housed in a 32-pin QFN package (5mm × 5mm, 0.5mm pitch) with exposed thermal pad soldered to PCB ground plane for optimal thermal dissipation (θJB = 20°C/W). The package is lead-free with NiPdAu finish and Pb-free bar-line indicator marking.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar clock fanout buffer applications.

Compared with IDT8T49N242 and NB3N551, SY75578LMG uniquely combines HCSL/LVDS dual-input MUX, 267MHz operation, and 130fsrms jitter in a thermally optimized QFN-32-making it the only option for PCIe Gen3 server backplanes requiring source redundancy and tight skew control.

Availability

SY75578LMG is available at Aetrix Electronics and suitable for blade servers, storage area networks, and IP routers requiring stable component supply, industrial-temperature reliability, and PCIe Gen3 timing compliance.

Supply support for SY75578LMG 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

Micrel, Inc. was a U.S.-based semiconductor company specializing in high-performance analog, RF, and timing solutions before its acquisition by Microchip Technology in 2015.

The SY75578LMG belongs to Micrel's PrecisionEdge™ ultra-low-jitter clock buffer product line, engineered specifically for PCIe, SATA, and high-speed SerDes timing distribution in enterprise computing and networking infrastructure.

FAQ

What is the maximum operating frequency supported by the SY75578LMG?

The SY75578LMG supports a maximum frequency of 267MHz, verified per AC Electrical Characteristics in the official datasheet. This specification enables full compliance with PCIe Gen3 reference clock requirements (100MHz nominal with 267MHz headroom) and supports high-speed SerDes applications where timing margin is critical. The SY75578LMG maintains specified jitter and skew performance up to this limit across the full industrial temperature range.

Does the SY75578LMG support both HCSL and LVDS input levels simultaneously?

Yes, the SY75578LMG accepts either HCSL or LVDS differential signals on both IN0 and IN1 input pairs, with defined VIH/VIL thresholds and common-mode voltage ranges (1.125V–1.375V) that accommodate both standards. The SY75578LMG does not require configuration or external components to switch between them-the input receivers are inherently compatible with both logic families.

How is input selection controlled on the SY75578LMG?

Input selection on the SY75578LMG is managed by the SEL pin (Pin 7), a single-ended TTL/CMOS-compatible control. When SEL = HIGH, the device routes IN0/IN0 to all outputs; when SEL = LOW, it routes IN1/IN1. The pin features an internal pull-up resistor, defaulting to IN0 selection if left unconnected-enabling fail-safe operation in redundant clock architectures using the SY75578LMG.

What is the purpose of the separate VDDIN and VDD pins on the SY75578LMG?

The SY75578LMG uses separate VDDIN (Pin 4) and VDD (Pins 12,17,24,29) supplies to isolate input-stage biasing from output-driver power domains. This separation improves PSRR, reduces supply-induced jitter coupling, and enhances noise immunity-particularly important in dense server PCB layouts where power rail noise can degrade phase jitter. Both rails operate at 3.3V ±5%.

Can the SY75578LMG be used in PCIe Gen4 systems?

The SY75578LMG is not rated for PCIe Gen4 (16GT/s) reference clock distribution, as its 267MHz maximum frequency and specified jitter performance (130fsrms @200MHz) align with PCIe Gen3 timing requirements. While it may function in some Gen4 implementations, the SY75578LMG lacks validation for Gen4 jitter budgets and eye diagram compliance. For Gen4, a newer-generation buffer such as Microchip SY89854L is recommended instead of the SY75578LMG.