A voice-band audio processor IC for CDMA applications
A 2.7 V voice-band audio processor (VBAP/sup TM/) IC for CDMA wireless handsets as presented, The chip consists of transmit (uplink) and receive (downlink) audio channels and runs at a nominal current consumption of 9.1 mA. The transmit channel has two differential microphone inputs with external filtering and gain option for signal conditioning before a /spl Sigma//spl Delta/ ADC. The transmit channel pre-emphasis filter, receive channel filter, part of transmit gain, receive gain, receive volume control and sidetone gains are achieved by a single DSP core. The receive channel has a differential and a single-ended speaker interface which can deliver 35 mW and 10 mW to a 32 /spl Omega/ load respectively. The PCM encoding and decoding can be achieved in both linear and /spl mu/-law companded modes. Due to the PLL/clock recovery circuitry the 13-bit /spl Sigma//spl Delta/ voiceband codec is immune to system clock jitter up to 37%.