ACS1790IMLT

Overview

The Semtech ACS1790T is a high-performance, low phase noise programmable frequency synthesizer with an integrated voltage-controlled oscillator (VCO). It operates within a 2.3–2.7 GHz VCO range and supports ultra-fine dynamic output frequency control with accuracy better than 1 ppb. The device features an I2C interface for full programmability and includes an integrated loop filter, phase-and-frequency detector, and output dividers. It provides three clock outputs: a high-speed LVPECL differential output (OUT1), a low-speed LVCMOS single-ended output (OUT2), and a feedback clock (FBCLK). The component meets RMS jitter requirements for Gigabit Ethernet, 10 Gigabit Ethernet, OC-48/STM-16, XAUI, and SONET/SDH applications.

Feature Summary

• Optimized for Synchronous Ethernet, SONET, and SDH operation with low phase noise performance.
• Integrated VCO operating between 2.3 GHz and 2.7 GHz with fractional divider dithering.
• Supports input clocks of 10, 12.8, 20, or 25 MHz via hardware selection pins.
• Provides four selectable I2C slave addresses to allow multiple devices on a single bus.

Applications

• Synchronous Ethernet systems requiring frequency locking to external references.
• SONET and SDH network equipment generating OC-48/STM-16 clocks.
• Gigabit and 10 Gigabit Ethernet transceivers meeting IEEE 802.3 jitter masks.
• XAUI interface clock generation for high-speed serial links.

Procurement Notes

Verify the specific ordering suffix against the manufacturer's current datasheet to confirm package type and temperature grade. Confirm RoHS compliance status as manufacturing processes may change. Check for end-of-life notifications or obsolescence warnings before finalizing procurement plans.

Selection Notes

Select the appropriate input clock frequency configuration using OSCFSEL0 and OSCFSEL1 pins to match the system reference source. Ensure power supply filtering meets the RF requirements for VDDA and VDDF to maintain phase noise specifications. Verify that the required output frequencies can be achieved within the +/- 500 ppm tuning range without triggering recalibration cycles.

Part Context

The ACS1790T belongs to Semtech's Advanced Communications Product Group lineup. It is designed to function as a companion to ToPSync devices for synchronized clock distribution or operate standalone for standard frequency generation. The device replaces discrete PLL components by integrating the VCO, PFD, and loop filter into a single QFN-24 package.

Replacement Considerations

Publicly confirmed substitute part numbers are not available in the provided documentation. Evaluate alternative frequency synthesizers based on matching VCO frequency ranges, output drive types (LVPECL/LVCMOS), and jitter performance metrics relative to the target application standards.