SI52131-A11AGM

Overview

The SI52131-A11AGM is a PCIe clock generator providing two differential outputs and one buffered single-ended reference clock. It accepts a 25 MHz crystal or clock input to generate compliant frequencies for PCIe Gen 1, Gen 2, and Gen 3 specifications. The device operates on a 3.3 V supply with a typical dynamic current of 45 mA. Key electrical parameters include a cycle-to-cycle jitter of 50 ps maximum for differential outputs and a long-term accuracy of 100 ppm. It features pin-selectable frequency options (100, 125, 200 MHz) and spread spectrum control within a 24-pin QFN package.

Feature Summary

• Sources two PCIe-compliant differential clocks and one 25 MHz reference clock from a 25 MHz input.
• Supports selectable output frequencies of 100, 125, and 200 MHz via SS pins.
• Features active low OE pins for independent output enable/disable and I2C configuration support.
• Includes triangular spread spectrum capability (-0.5% down spread) for EMI reduction.

Applications

• PCI-Express Gen 1, Gen 2, and Gen 3 compliant systems
• Network Attached Storage (NAS)
• Wireless Access Points and Routers
• Multi-function Printers

Procurement Notes

Verify the specific ordering suffix against the manufacturer's official documentation. The 'GM' suffix indicates a 24-pin QFN package in an extended temperature range (-40°C to +85°C). Confirm whether the required variant is the tray-packaged 'GM' version or the tape-and-reel 'GMR' version, as packaging differences exist within the family.

Selection Notes

Select this component when a dual-differential clock source with a dedicated 25 MHz reference is required for PCIe applications. Ensure the design utilizes a parallel resonance crystal with appropriate load capacitance (12–15 pF) to achieve specified long-term accuracy. Verify that the 3.3 V power supply meets the ±5% tolerance requirements for stable operation.

Part Context

This part belongs to the Skyworks Si52131 series of high-performance clock generators. The A11A designation specifies the functional configuration including the 25 MHz reference output and specific frequency/spread capabilities. The device is designed for consumer and embedded applications requiring low power consumption and small footprint solutions.

Replacement Considerations

Publicly confirmed substitute part numbers are not available in the provided documentation. Designers should consult Skyworks technical support or the ClockBuilder Pro tool for validated alternatives if the SI52131-A11AGM is unavailable.

FAQ

How is the spread spectrum enabled?

Spread spectrum is enabled by setting the SS0 pin high while keeping the SS1 pin low (SS1=0, SS0=1). This configures the differential outputs to -0.5% down spread at a modulation frequency of approximately 31.5 kHz.

What is the default frequency output upon power-up?

The default state for the SS pins is 00, which corresponds to a 100 MHz differential output frequency with spread spectrum disabled.

Can the REF output be disabled independently?

Yes, the 25 MHz reference output can be disabled by pulling the OE_REF1 pin high or by setting the corresponding bit in Control Register 0 via the I2C interface.