GENERAL DESCRIPTION
The PCA1070 is a CMOS integrated circuit performing all speech and line interface functions in fully electronic telephone sets. The device requires a minimum of external components. The transmission parameters are programmable via the I2C-bus. This makes the IC adaptable to nearly all worldwide country requirements and to a various range of speech transducers, without changing the (few) external components.

FEATURES
• Line interface with:
   – Voltage regulator with programmable DC voltage drop
   – Programmable set impedance
   – Output to control an external switching MOS transistor for pulse dialling
   – Programmable DC voltage during pulse dialling
   – Circuitry for short DC settling time
• Interface to peripheral circuits with:
   – Supply for microcontroller and DTMF diallers
   – Input to sense supply voltage of microcontroller and output for reset of microcontroller
   – I2C-bus (programming of parameters, control of all logic signals)
   – High impedance DTMF signal input
   – Input for external oscillator signal with on-chip DC blocking
   – Power-down via the I2C-bus
   – Stabilized supply for electret microphone
• Microphone and DTMF amplifiers:
   – Low-noise microphone preamplifier suitable for various types of microphones
   – Symmetrical high impedance microphone preamplifier inputs
   – Programmable gain for microphone and DTMF channels
   – Sending mute via the I2C-bus to disable microphone amplifier and enable DTMF amplifier
   – Sending mute also to be used as privacy switch
   – Dynamic limiting (speech controlled) to prevent distortion of line signal and sidetone; programmable maximum sending level
• Receiving amplifier:
   – Suitable for various types of earpieces (including piezo)
   – Programmable gain and hearing protection level
   – Receiving mute via the I2C-bus to disable receiving amplifier and enable DTMF confidence tone
   – On-chip anti-sidetone circuit with programmable sidetone balance
   – Confidence tone in the earpiece during DTMF dialling
• Facility to regulate parameters with line current:
   – Value of DC line current (bit code) readable via the I2C-bus
   – Line loss compensation with fully software programmable characteristics (control range, stop current) of microphone/earpiece/DTMF amplifiers
   – Fully software programmable control of sidetone balance and DC voltage drop as a function of line length.

APPLICATIONS
• Wired telephony (basic till feature phones)
• Combi-terminals (e.g. telephone and answering machine or FAX)
• Modems and base units of cordless telephones.