ACS1790IMLTRT

Overview

The ACS1790IMLTRT is a high-performance, low phase noise programmable frequency synthesizer with an integrated voltage-controlled oscillator (VCO). Designed for Synchronous Ethernet, SONET, and SDH applications, it generates outputs locked to an external reference or operates standalone. The device features ultra-fine dynamic output frequency control via an I2C interface, supporting LVPECL and LVCMOS outputs. It meets RMS jitter requirements for Gigabit Ethernet, 10 Gigabit Ethernet, and OC-48/STM-16 standards.

Feature Summary

• Integrated VCO operating between 2.3 GHz and 2.7 GHz with fractional divider dithering for ultra-fine frequency steps.
• Low phase noise performance: Typical RMS jitter of 0.56 ps (OC-48/STM-16), 0.15 ps (1G Ethernet), and 0.29 ps (10G Ethernet).
• Supports 10, 12.8, 20, or 25 MHz input clock frequencies with selectable default outputs at reset.
• I2C-bus interface with four selectable slave addresses for multi-device configurations.

Applications

• Synchronous Ethernet systems requiring precise clock derivation from local or external references.
• SONET and SDH network equipment compliant with ANSI T1.105.03 and ITU-T G.813 standards.
• Clock generation for Gigabit Ethernet (IEEE 802.3) and 10 Gigabit Ethernet interfaces.
• Standalone frequency generation for general-purpose timing applications.

Procurement Notes

Verify the specific ordering suffix against the manufacturer's current documentation to confirm packaging details such as tape and reel quantities. Ensure compatibility with the required I2C bus voltage levels and check for any recent product change notifications regarding pinout or electrical specifications before finalizing procurement.

Selection Notes

Select this component when low phase noise and high frequency stability are critical for synchronous networking protocols. The integrated VCO simplifies design by eliminating external components typically required for PLL synthesis. Consider the available output drivers (LVPECL and LVCMOS) to match the downstream receiver requirements without additional level shifting circuitry.

Part Context

The ACS1790T belongs to Semtech's Advanced Communications Product Group portfolio, specifically targeting precision timing solutions for telecommunications infrastructure. It is often used in conjunction with ToPSync devices to simplify system architecture by reducing the bill of materials and component count in complex synchronization networks.

Replacement Considerations

Publicly confirmed substitute part numbers are not available in the provided source material. Evaluate alternative frequency synthesizers based on matching VCO range, jitter performance masks, and package dimensions if direct replacement is necessary.

FAQ

What is the typical RMS jitter performance for OC-48/STM-16 applications?

The typical RMS jitter performance for OC-48/STM-16 (ANSI T1.105.03 & ITU-T G.813) is 0.56 ps within the 12 kHz to 20 MHz bandwidth.

How does the device handle frequency adjustments after calibration?

Once calibrated, the output frequency can be adjusted by up to +/- 500 ppm without requiring further calibration. Adjustments outside this range necessitate initiating a new calibration cycle.

What input clock frequencies are supported?

The device supports 10, 12.8, 20, or 25 MHz input clock frequencies, which can be selected via hardware pins.