Electronic Design

Codec And SLIC Merged Into Single-Chip VoIP Solution

Voice over Internet Protocol (VoIP) is finding homes everywhere. The Le88111, a single-channel VoIP codec from Legerity, supports these applications. Yet this codec also incorporates the complete subscriber line interface circuits (SLICs) on the same chip (see the figure). As a result, it implements all BORSCHT functions associated with a common plain-old-telephone-service phone.

These functions—which include battery feed, overvoltage protection, ringing, line supervision, codec, hybrid, and test—call for high-voltage components. Typically, such components aren't available in CMOS. Yet the company's proprietary designs and processes enable these chips to handle up to 150 V peak.

The Le88111 also features an integrated high-voltage switching regulator controller and programmable ringing. It handles ringing voltages up to 100 V. (The Le88131 can handle up to 150 V.) Other programmable functions include ac impedance, balance impedance and gain, dc feed voltage and current limiting, ringing frequency, 12- or 16-kHz metering, and loop closure.

The codec uses G.711 standard µ-law or A-law companding or 16-bit linear coding. Moreover, the chip features universal caller ID generation and selectable wideband or narrow-band pulse-code modulation (PCM). A 150-mW 3- or 5-V relay driver is built in as well.

Thanks to subscriber and loop test capability, the carrier can perform tests remotely on the circuits. These tests include comprehensive line sensing, integrated self test, line fault detection, and reporting (including loop supervision and ac-dc faults).

Available now, the Le88111 and Le88131 come in a 44-pin eLQFP. Pricing is $2.50 each in high volumes.

Legerity Inc.

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