Skyworks Solutions Inc. SL28748ELCT

Overview

SL28748ELCT from Silicon Laboratories is an EProClock® programmable clock generator optimized for Intel Calpella chipset platforms, delivering 100 MHz differential CPU/SRC/SATA clocks, 96 MHz DOT96, dual 27 MHz video clocks (spread and non-spread), and buffered 14.318 MHz reference output. It integrates voltage regulation, on-die termination resistors, I²C programmability, and triangular spread-spectrum modulation for EMI reduction in desktop and mobile motherboard designs.

For engineers reviewing the SL28748ELCT datasheet, SL28748ELCT pinout, SL28748ELCT application, or SL28748ELCT equivalent, this device supports Intel CK505 Clock Revision 1.0 compliance, PCI-Express Gen 2 timing requirements, hybrid video clocking (DOT96 + 27 MHz SS/NSS), and scalable VDD_IO (3.3 V to 1.05 V) for flexible system-level power management.

Technical Context

The SL28748ELCT implements a multi-PLL architecture with dedicated PLLs for CPU (100/133 MHz), SRC/SATA (100 MHz), DOT96 (96 MHz), and 27 MHz video clocks - each independently configurable via I²C. Its EProClock® non-volatile programmability enables field-updatable frequency sets, differential skew/duty cycle/amplitude control, and custom spread-spectrum profiles without hardware changes.

It features dual-function pins including CKPWRGD/PD# for power-good latching and asynchronous power-down, CPU_STP# for synchronous CPU clock gating, and FS for hardware-selectable CPU frequency (100 MHz or 133 MHz). All differential outputs meet PCIe Gen2 phase jitter specs (≤3.1 ps RMS), and single-ended outputs support wireless-friendly 3-bit slew rate control.

Key Specifications

Pinout & Package

SL28748ELCT uses a 32-pin QFN package (5 mm × 5 mm, 0.5 mm pitch) with exposed thermal pad. Power and ground pins are distributed across all four sides for optimal noise suppression and thermal dissipation in high-density motherboard layouts.

Key Features

Applications

Equivalent & Alternatives

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

Compared with ICS9LPRS405AGT and Si53320-A-GM, SL28748ELCT uniquely combines Intel Calpella-validated clock trees, hybrid video clocking, and field-programmable EProClock® technology - enabling one-time hardware design with post-deployment timing optimization.

Availability

SL28748ELCT is available at Aetrix Electronics and suitable for desktop motherboard timing, laptop platform clocking, embedded industrial PC designs, and PCIe add-in card synchronization requiring stable component supply and long-term lifecycle support.

Supply support for SL28748ELCT 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

Silicon Laboratories is a fabless semiconductor company specializing in timing, MCU, and connectivity solutions for embedded systems, with deep expertise in clock synthesis and jitter optimization.

The SL28748ELCT belongs to Silicon Labs' EProClock® family, designed specifically to replace fixed-frequency clock generators in Intel chipset platforms with field-upgradable, EMI-optimized, multi-output timing solutions.

FAQ

What is the primary application target for the SL28748ELCT?

The SL28748ELCT is engineered as the core clock generator for Intel Calpella chipset-based platforms, including desktop motherboards and mobile computing systems. It delivers synchronized CPU, SRC, SATA, DOT96, and dual 27 MHz video clocks while meeting Intel CK505 Revision 1.0 and PCIe Gen2 timing specifications. Its EProClock® programmability allows board designers to optimize signal integrity and EMI performance without hardware revisions - making SL28748ELCT ideal for high-volume, cost-sensitive motherboard designs requiring long-term supply stability.

Does the SL28748ELCT support both spread-spectrum and non-spread 27 MHz video clocks simultaneously?

Yes, the SL28748ELCT provides two independent 27 MHz single-ended outputs: Pin 6 (27M_NSS) delivers a non-spread-spectrum clock, and Pin 7 (27M_SS) delivers a spread-spectrum version. Both are generated concurrently and can drive separate display interfaces (e.g., LVDS and eDP) without external multiplexing. The spread profile is configurable via registers (Byte 13 and Table 4), and both outputs maintain ≤50 ppm long-term accuracy and ≤300 ps cycle-to-cycle jitter - confirming SL28748ELCT's suitability for hybrid video timing architectures.

How does the FS pin affect CPU clock frequency selection on the SL28748ELCT?

The FS pin (Pin 30) is sampled once at CKPWRGD assertion to select between 100 MHz and 133 MHz CPU clock outputs. When FS is pulled HIGH before CKPWRGD goes active, SL28748ELCT configures CPU0/CPU1 for 100 MHz operation; when FS is LOW, it defaults to 133 MHz. This one-shot sampling ensures deterministic boot behavior and eliminates race conditions. The FS pin includes a 100 kΩ internal pull-down resistor, simplifying strapping - and SL28748ELCT retains the selected frequency throughout operation unless reprogrammed via I²C.

What PCIe Gen2 compliance metrics does the SL28748ELCT meet for its SRC outputs?

The SL28748ELCT SRC outputs (Pins 10/11 and 13/14) meet PCIe Gen2 reference clock specifications with ≤3.1 ps RMS phase jitter in the low-band (<1.5 MHz), measured under JEDEC JESD216 conditions (PLL BW 8–16 MHz, ζ = 0.54, Td = 10 ns). Its differential amplitude is programmable (0.30–1.00 V), and integrated 100 Ω termination eliminates external resistors. These characteristics - verified in the AC Electrical Specifications table (Page 14) - confirm SL28748ELCT's readiness for Gen2 link training and stable high-speed serial interface operation.

Can the SL28748ELCT operate in industrial temperature range?

No - the SL28748ELCT variant is rated for commercial temperature range (0 °C to +85 °C), as specified in the Ordering Information table (Page 18). For industrial operation (–40 °C to +85 °C), the correct part number is SL28748ELIT (tape-and-reel) or SL28748ELI (tray). While SL28748ELCT shares the same silicon die and functionality, its qualification and screening are limited to commercial conditions; using SL28748ELCT outside 0–85 °C voids parametric guarantees and may impact long-term reliability. Always match the suffix (C/T vs. I/IT) to the target application environment.