SY89840UMG-TR

Overview

The SY89840UMG-TR is a Precision LVPECL Runt Pulse Eliminator (RPE) 2:1 multiplexer designed for redundant source switchover applications. It operates from a 2.5V ±5% or 3.3V ±10% supply and supports frequencies up to 2.0 GHz. The device features an ultra-low jitter design with typical RMS phase jitter of 140 fs and MUX crosstalk-induced jitter of 0.7 ps rms. Propagation delay ranges from 460 ps to 880 ps depending on input voltage swing, with rise/fall times under 190 ps. It accepts AC or DC-coupled differential inputs as small as 100 mV single-ended or 200 mV differential without external level shifting.

Feature Summary

• Unique Runt Pulse Eliminator (RPE) circuit prevents short cycles or runt pulses during clock switchover transitions.
• Fail-Safe Input (FSI) protection prevents metastable conditions when the selected input clock fails to a DC voltage below 100mV.
• Patent-pending 3-pin input termination architecture allows direct interface to CML, PECL, and LVDS signals without external termination networks.
• Internal power-on reset logic ensures stable startup states via an external capacitor on the CAP pin.

Applications

• Redundant clock switchover systems
• Failsafe clock protection circuits
• Enterprise server infrastructure
• Test and measurement equipment

Procurement Notes

Verify that the specific ordering suffix matches the required package type and reel configuration. Confirm the component meets RoHS compliance standards and lead finish specifications prior to integration. Ensure the supplier provides valid traceability documentation for the manufacturing lot. Check for any recent product change notifications regarding packaging or material composition updates.

Selection Notes

Select this component when glitch-free switchover between two asynchronous clock sources is critical. The device is suitable for designs requiring low jitter performance and compatibility with various differential signaling standards including LVPECL, CML, and LVDS. Consider the industrial temperature range and supply voltage flexibility when designing power delivery networks.

Part Context

This part belongs to Micrel's Precision Edge product line, now under Microchip Technology. It is specifically engineered for high-speed digital applications where signal integrity during source switching is paramount. The QFN-16 package facilitates compact PCB layouts while maintaining thermal performance for industrial environments.

Replacement Considerations

SY89841U: Precision LVDS variant with similar RPE functionality but different output signaling standard.

FAQ

How does the Fail-Safe Input function protect against clock failure?

If the selected input pair drops below the minimum amplitude requirement (less than 100mV single-ended or 200mV differential), the FSI circuit latches the output to the last valid clock state, preventing oscillations or metastable conditions.

What is the purpose of the CAP pin?

The CAP pin connects to an external capacitor to control the Power-On Reset (POR) delay. This ensures the internal RPE logic starts up in a known state once the power supply stabilizes above 2.3V.