Programmable SLIC for advanced voice-over-IP

October 21, 2015 // By Graham Prophet
Silicon Labs' latest family of subscriber line interface circuits (SLICs) offers the lowest power consumption, smallest footprint, and highest levels of integration and programmability for the voice-over-IP (VoIP) gateway market.

The single- and dual-channel Si32x8x ProSLIC family provides a subscriber line interface solution for a wide range of VoIP customer premises equipment (CPE) including cable gateways, xDSL integrated access devices, xPON optical network terminals, fibre to the home (FTTH), fibre to the building (FTTB) and wireless fixed terminals.

The VoIP market, Silicon Labs says, continues to grow steadily each year, driven primarily by new FTTH/FTTB deployments and upgrades of existing xDSL and cable gateways as consumers demand higher broadband speeds and new services.

The Si32x8x ProSLIC family provides configurability to ensure future-proofed one- and two-channel foreign exchange station (FXS) telephony interfaces in a compact, single-chip solution. The ProSLIC devices minimise SLIC power consumption by using flexible, integrated tracking DC/DC controllers that support ultra-low-cost capacitive boost configuration technology. They also reduce power by using Silicon Labs' low-power ringing (LPR) technology and an ultra-low-power 50 mW per channel on-hook mode. Smart ringing technology available in dual-channel ProSLIC devices also enables the use of cost-effective power adapters in two-channel CPE designs by typically reducing the required peak current by more than 300 mA. These on-chip innovations make the highly integrated ProSLIC devices the most power-efficient SLIC products available, while significantly reducing system BOM cost.

The ProSLIC family offers an integrated level shifter/driver, enabling a direct connection to a DC-SC converter's power transistor regardless of input voltage. This eliminates the need for a separate MOSFET pre-drive circuit required by competing SLIC designs, reducing the cost and footprint of a two-channel design by at least 12 external devices. The Si32x8x devices interface to leading CPE SoCs offering a PCM/SPI or ISI digital interface. When coupled with Silicon Labs' Si88x4x digital isolators through a 3-wire ISI interface, the Si32x8x family provides the only single-transformer isolated voice solution.

The Si32x8x family claims the smallest single-channel SLICs in QFN package options as small as 5 x 6 mm, as well as a very compact 7 x 7 mm dual-channel solution. The Si32x8x BOM footprint is only 4.2 cm² per FXS channel - the smallest SLIC footprint in the industry. This tiny device size enables the lowest BOM cost and smallest footprint per channel for multiline CPE gateways.