MC34118

HTC Korea MC34118 Voice Switched Speakerphone Circuit incorporates the necessary amplifiers, attenuators, level detectors, and control algorithm to form the heart of a high  quality hands-free speakerphone system. Included are a microphone amplifier with  adjustable gain and MUTE control, Transmit and Receive attenuators which operate in a  complementary manner, level detectors at both input and output of both attenuators,  and background noise monitors for both the transmit and receive channels. A Dial Tone Detector prevents the dial tone from being attenuated by the Receive background noise monitor circuit. Also included are two line driver amplifiers which can be used to form a hybrid network in conjunction with an external coupling transformer. A high-pass filter can be used to filter out 60Hz noise in the receive channel, or for other filtering  functions. A Chip Disable pin permits powering down the entire circuit to conserve power on long loops where loop current is at a minimum. The MC34118 may be  operated from a power supply, or it can be powered from the telephone line, requiring typically 5.0mA. The MC34118 can be interfaced directly to Tip and Ring (through a  coupling transformer) for stand-alone operation, or it can be used in conjunction with a  handset speech network and/or other features of a featurephone.

MC34118 features :

• Improved attenuator gain range: 52dB between transmit and receive
•  Low voltage operation for line-powered application (3.0V to 6.5V)
•  4-point signal sensing for improved sensitivity
• Background noise monitors for both transmit and receive paths
•  Microphone amplifier gain set by external resistors –
  Mute function included
•  Chip disable for active/standby operation
•  Dial tone detector to inhibit receive idle mode during dial tone presence
•  Standard 28-pin plastic DIP package and SOP package available
•  Compatible with MC34119 speaker amplifier