Semtech Adds Jitter Attenuating and Multiplying PLL Devices for Cost-Sensitive Telecom Systems

Semtech Corp has announced the ACS8946 and ACS8944 jitter attenuating and multiplying (JAM) phase locked loop (PLL) devices for generating low jitter output clocks for low-cost SONET/SDH and Gigabit Ethernet line cards. The new devices are part of Semtech’s JAM PLL family, a sister family to the synchronous equipment timing source (SETS) product family.

The ACS8946 and ACS8944 are designed for clock de-jitter applications in telecom line cards supporting speeds up to OC-12/STM-4. They deliver output jitter of 2.8 ps rms to packet framing or serializing devices - well below the Telcordia GR-253 standard of 16 ps rms for OC-12.

Both JAM PLL devices offer frequency programmability to any SONET/SDH rate, including 19.44 MHz, 38.88 MHz, 77.76 MHz and 155.52 MHz. The ACS8946 and ACS8944 also feature an integrated voltage-controlled oscillator (VCO) to reduce parts count and build cost.

The ACS8946 features a built-in reference switch that allows it to serve as a complete SETS solution by providing frequency translation and line-card protection from lost clock signals. It has two differential, frequency-programmable low-voltage positive emitter coupled logic (LVPECL) reference inputs and one differential synchronous input. It has four outputs, programmable as LVPECL or current-mode logic (CML). The device can also be used on Gigabit Ethernet line cards operating at either 125 MHz or 156.25 MHz, with output frequency multiplication up to 625 MHz.

The ACS8944 has a single differential LVPECL input and a single differential LVPECL output, and provides frequency translation. It can be used with any synchronization device for a complete SETS solution, including Semtech’s ACS8525, ACS8526 and ACS8527 line card protection devices.

Many line cards today rely on a de-jitter solution built out of discrete components, which involves a higher part count and takes a significant engineering effort to meet Telcordia standards. The ACS8946 and ACS8944 are ideally suited for DSL access multiplexers, multi-service provisioning platforms, or ATCA-based telecom systems.

“The performance, integration and features of these new JAM PLLs enables designers to develop cost effective sync solutions for jitter sensitive high-speed systems and achieve system standard compliance,” said Stewart Kelly, director of Semtech's Advanced Communications Division. “With the JAM PLL family pairing with our successful SETS product line, Semtech has become a one-stop shop to fulfill all SONET/SDH network element, standards-compliant clocking requirements.”

Both devices are available in a 7mm x 7mm leadless QFN48 package that is lead-free and RoHS and WEEE compliant .