A high-performance analog front-end 13-bits linear codec for 3V digital cellular phones

Abstract

A low-voltage, low-power, CMOS programmable Analog Front-End IC for 3 V digital cellular phone applications is presented. The chip can be configured either as a classical A//spl mu/ law PCM codec or as a 13-bits linear codec. Its high performance speech interface results in a microphone preamplifier with about 0.5 mV offset and 1.3 /spl mu/V/sub rms/ input-referred noise for the transmit channel, while it is capable of driving loads up to 27 /spl Omega/ or 50 nF with 4 V/sub pp/, output voltages and -80 dB of THD in the receive path. A tone generator that can also be used for ringing or DTMF signaling purpose, and a dedicated pulse-width modulated output for a buzzer complete the chip functions. All programmable functions can be accessed via a standard four wire control interface. These performances have been achieved from a 3 V supply with operative and stand-by power consumptions of 21 mW and 1.5 /spl mu/W, respectively. Chip area is 22.7 mm/sup 2/ in a 0.8 /spl mu/ CMOS process.