Skyworks Solutions Inc. SI5335A-B15687-GM

Overview

SI5335A-B15687-GM from Skyworks Solutions is a web-customizable, quad-output clock generator/buffer IC with MultiSynth fractional synthesis. It delivers four independent, non-integer-related frequencies up to 350 MHz, supports LVPECL/LVDS/HCSL/CMOS/SSTL outputs, achieves 0.7 ps RMS phase jitter, and operates across –40 to +85 °C in PCIe Gen 1–4 timing systems.

For engineers reviewing the SI5335A-B15687-GM datasheet, SI5335A-B15687-GM pinout, SI5335A-B15687-GM application, or SI5335A-B15687-GM equivalent, key selection criteria include PCIe Gen 4 common-clock jitter compliance (0.15–0.45 ps RMS), dual PLL loop bandwidth options (475 kHz / 1.6 MHz), loss-of-signal alarm, and pin-selectable frequency plans for multi-configuration system support.

Technical Context

The SI5335A-B15687-GM implements a single high-performance PLL with patented MultiSynth fractional dividers per output bank, enabling zero-ppm synthesis error across all four output banks. Each bank supports one differential pair or two single-ended outputs, with independent voltage control (1.5/1.8/2.5/3.3 V) and format selection (LVPECL, LVDS, HCSL, CMOS, SSTL, HSTL).

It accepts flexible references: 25/27 MHz crystal, or AC-coupled CMOS/SSTL/HSTL/differential inputs from 10–350 MHz. Two selectable PLL loop bandwidths (475 kHz for DSL jitter attenuation; 1.6 MHz for PCIe) and five user-assignable control pins (SSENB, RESET, FS[1:0], OEB) enable system-level timing control without firmware.

Key Specifications

Pinout & Package

SI5335A-B15687-GM uses a 24-lead QFN package (4 mm × 4 mm) with exposed thermal pad. Pin functions are defined per Skyworks Rev. 1.4 datasheet, including dual differential reference inputs (XA/CLKIN, XB/CLKINB), four differential clock output pairs (CLK0A/B through CLK3A/B), three dedicated control pins (P1, P2, P3), two dual-function pins (P5, P6), loss-of-signal indicator (LOS), and multiple VDDO/VDD/GND terminals.

Key Features

Applications

Equivalent & Alternatives

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

Compared with Si5345A-D-GM and ICS8430I-01T, the SI5335A-B15687-GM uniquely balances web-based configurability, PCIe Gen 4 readiness, and industrial temperature operation in a compact 24-QFN, making it optimal for mid-tier networking and embedded computing where flexibility and qualification matter more than maximum channel count or absolute lowest jitter.

Availability

SI5335A-B15687-GM is available at Aetrix Electronics and suitable for PCIe Gen 4 server motherboards, 10G Ethernet switches, broadcast video equipment, and telecom line cards requiring stable component supply, long-term lifecycle support, and factory-programmed configuration.

Supply support for SI5335A-B15687-GM 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

Skyworks Solutions is a global leader in analog and mixed-signal semiconductors, specializing in RF, timing, and connectivity solutions for infrastructure, automotive, and mobile markets.

The SI5335 family is designed as a highly configurable, any-frequency clock generator/buffer targeting high-reliability applications in data center, enterprise networking, and broadcast video where PCIe compliance, low jitter, and multi-configuration flexibility are critical.

FAQ

What is the guaranteed phase jitter performance of the SI5335A-B15687-GM under PCIe Gen 4 conditions?

The SI5335A-B15687-GM delivers 0.15–0.45 ps RMS phase jitter (12 kHz–20 MHz) when configured for PCIe Gen 4 common-clock operation at 100 MHz HCSL output with 1.6 MHz PLL loop bandwidth, fully compliant with PCI-Express Base Specification 4.0 rev. 0.5. This value is measured using the Intel Clock Jitter Tool Ver. 1.6.4 and verified per AN562 methodology. The SI5335A-B15687-GM maintains this performance across –40 to +85 °C.

Does the SI5335A-B15687-GM support spread spectrum clocking (SSC) for EMI reduction?

Yes, the SI5335A-B15687-GM supports PCIe-compliant spread spectrum clocking via its dedicated SSENB pin. When asserted, it applies –0.5% down-spread modulation at 31.5 kHz (default), reducing electromagnetic interference without compromising timing integrity. SSC is configurable per output bank and can be enabled/disabled dynamically during operation. The SI5335A-B15687-GM's MultiSynth architecture ensures zero frequency error even with SSC active.

Can the SI5335A-B15687-GM operate as a pure clock buffer without PLL involvement?

Yes, the SI5335A-B15687-GM supports true clock buffer mode (PLL bypass), where input clocks pass directly to outputs with only 2.5–4 ns propagation delay and no added synthesis jitter. In this mode, it accepts 5–350 MHz inputs (differential or single-ended), provides output-enable control per bank, and retains loss-of-signal detection. Buffer mode draws just 12 mA core current, making the SI5335A-B15687-GM ideal for low-power timing distribution.

How many independent voltage domains does the SI5335A-B15687-GM support for its outputs?

The SI5335A-B15687-GM supports four independent output voltage domains (VDDO0–VDDO3), each configurable for 1.5 V, 1.8 V, 2.5 V, or 3.3 V. This allows simultaneous generation of mixed-voltage clocks - for example, 1.8 V LVDS for an FPGA I/O bank and 3.3 V CMOS for a microcontroller - without level shifters. Each domain powers one output bank (CLK0, CLK1, CLK2, CLK3), ensuring clean signal integrity and PSRR isolation. The SI5335A-B15687-GM's core VDD is separate and supports 1.8/2.5/3.3 V operation.

Is factory programming required for the SI5335A-B15687-GM to function, or can it run from default configuration?

The SI5335A-B15687-GM ships with a factory-programmed default configuration that enables basic clock generation from a 25 MHz crystal or differential input, with all outputs active at default frequencies and formats. No external EEPROM or programming is needed for immediate operation. However, full utilization of features - such as custom frequencies, spread spectrum, multi-configuration pin selection (FS[1:0]), or optimized jitter settings - requires configuration via Skyworks' ClockBuilder Pro web utility and factory programming. The SI5335A-B15687-GM retains its programmed configuration permanently.